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<a href="/2019/04/10/Android-插件化实现方式（Hook）/" class="post-title-link" itemprop="url">Android_插件化实现方式（Hook）</a>
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<time title="创建时间：2019-04-10 13:28:02 / 修改时间：13:36:43" itemprop="dateCreated datePublished" datetime="2019-04-10T13:28:02+08:00">2019-04-10</time>
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<h4 id="一、首先我们要找到Hook的点"><a href="#一、首先我们要找到Hook的点" class="headerlink" title="一、首先我们要找到Hook的点"></a>一、首先我们要找到Hook的点</h4><h5 id="1-分析"><a href="#1-分析" class="headerlink" title="1. 分析"></a>1. 分析</h5><ul>
<li>我们先大概看下activity的启动流程(图片来自Android 插件化开发指南)<br><img src="https://note.youdao.com/yws/api/personal/file/WEBbee44fcd6b816bccace9444417d927e2?method=download&shareKey=c4175ab0d0221636865936e41ab3163e" alt="image"></li>
<li>当我们调用startActivity的时候，AMS对我们要启动的Activity进行检查，是否在AndroidManifest中声明过，如果没有就报没有在AndroidManifest的错误。这个时候需要欺骗AMS，我们需要hook，要它去检查一个我们预配置的Activity，通过AMS的检查。</li>
<li>为什么不能直接hook掉AMS，AMS是系统的进程，管理者所有app的启动，不仅仅只是我们自己的app。</li>
</ul>
<h5 id="2-看看源码怎么启动的（主要就是拦截这个方法startActivity）"><a href="#2-看看源码怎么启动的（主要就是拦截这个方法startActivity）" class="headerlink" title="2. 看看源码怎么启动的（主要就是拦截这个方法startActivity）"></a>2. 看看源码怎么启动的（主要就是拦截这个方法startActivity）</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">//通过ActivityManagerNative.getDefault()获取一个对象，开始启动新的Activity</span><br><span class="line"> int result = ActivityManagerNative.getDefault().startActivity(whoThread,</span><br><span class="line"> </span><br><span class="line"> who.getBasePackageName(), intent,intent.resolveTypeIfNeeded(who.getContentResolver()),</span><br><span class="line"> </span><br><span class="line"> token, target != null ? target.mEmbeddedID : null,</span><br><span class="line"> requestCode, 0, null, options);</span><br></pre></td></tr></table></figure>
<h5 id="3-看看代码的实现"><a href="#3-看看代码的实现" class="headerlink" title="3. 看看代码的实现"></a>3. 看看代码的实现</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">private Context mContext;</span><br><span class="line">private Class<?> mProxyClass;</span><br><span class="line"></span><br><span class="line">private String TAG = HookUtil.class.getName();</span><br><span class="line">private final String EXTRA_ORIGIN_INTENT = "EXTRA_ORIGIN_INTENT";</span><br><span class="line"></span><br><span class="line">public HookUtil(Context context, Class<?> proxyClass) {</span><br><span class="line"> this.mContext = context.getApplicationContext();</span><br><span class="line"> this.mProxyClass = proxyClass;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">public void hookStartActivity() throws Exception {</span><br><span class="line"> //1. 通过反射，拿到IActivityManager对象；</span><br><span class="line"> Class amnClass = Class.forName("android.app.ActivityManagerNative");</span><br><span class="line"> //2. 获得指定的私有属性</span><br><span class="line"> Field gDefaultField = amnClass.getDeclaredField("gDefault");</span><br><span class="line"> gDefaultField.setAccessible(true);</span><br><span class="line"> // 获取字段上面的值传递null 证明是属性是static的,此处返回的是</span><br><span class="line"> // new Singleton<IActivityManager>()</span><br><span class="line"> Object gDefault = gDefaultField.get(null);</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> Class singletonClass = Class.forName("android.util.Singleton");</span><br><span class="line"> Field mInstanceField = singletonClass.getDeclaredField("mInstance");</span><br><span class="line"> mInstanceField.setAccessible(true);</span><br><span class="line"> //不是static的方法 ，需要传入当前使用的对象 此处返回的是IActivityManager</span><br><span class="line"> Object iamInstance = mInstanceField.get(gDefault);</span><br><span class="line"></span><br><span class="line"> Class iamClass = Class.forName("android.app.IActivityManager");</span><br><span class="line"> Object proxyInstance = Proxy.newProxyInstance(HookUtil.class.getClassLoader(),</span><br><span class="line"> new Class[]{iamClass},</span><br><span class="line"> // InvocationHandler 必须执行者，谁去执行</span><br><span class="line"> new StartActivityInvocationHandler(iamInstance));</span><br><span class="line"></span><br><span class="line"> //f.set(obj, "刘德华");</span><br><span class="line"> mInstanceField.set(gDefault, proxyInstance);</span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> private class StartActivityInvocationHandler implements InvocationHandler {</span><br><span class="line"> // 方法执行者</span><br><span class="line"> private Object mObject;</span><br><span class="line"></span><br><span class="line"> public StartActivityInvocationHandler(Object object) {</span><br><span class="line"> this.mObject = object;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> @Override</span><br><span class="line"> public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {</span><br><span class="line"> // 替换Intent,过AndroidManifest.xml检测</span><br><span class="line"> if (method.getName().equals("startActivity")) {</span><br><span class="line"> Log.e(TAG,"Activity已经开始启动");</span><br><span class="line"> Log.e(TAG,"小弟到此一游！！！");</span><br><span class="line"> // 1.首先获取原来的Intent</span><br><span class="line"> Intent originIntent = (Intent) args[2];</span><br><span class="line"></span><br><span class="line"> // 2.创建一个安全的</span><br><span class="line"> Intent safeIntent = new Intent(mContext, mProxyClass);</span><br><span class="line"> args[2] = safeIntent;</span><br><span class="line"></span><br><span class="line"> // 3.绑定原来的Intent</span><br><span class="line"> safeIntent.putExtra(EXTRA_ORIGIN_INTENT, originIntent);</span><br><span class="line"> }</span><br><span class="line"> return method.invoke(mObject, args);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="4-初始化插件"><a href="#4-初始化插件" class="headerlink" title="4. 初始化插件"></a>4. 初始化插件</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line">protected void onCreate(Bundle savedInstanceState) {</span><br><span class="line"> super.onCreate(savedInstanceState);</span><br><span class="line"> setContentView(R.layout.activity_main);</span><br><span class="line"></span><br><span class="line"> ButterKnife.bind(this);</span><br><span class="line"> mButton.setText("test");</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> //初始化插件</span><br><span class="line"> HookUtil hookUtil =</span><br><span class="line"> new HookUtil(this, ProxyActivity.class);</span><br><span class="line"> try {</span><br><span class="line"> hookUtil.hookStartActivity();</span><br><span class="line"> } catch (Exception e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> </span><br><span class="line"> @OnClick(R.id.btn)</span><br><span class="line"> public void btnOnclick() {</span><br><span class="line"> Intent intent = new Intent(MainActivity.this, Main3Activity.class</span><br><span class="line"> );</span><br><span class="line"> startActivity(intent);</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<h5 id="5-打印结果-没有报错，打印了当前activity的stop方法-证明通过AMS的检查了"><a href="#5-打印结果-没有报错，打印了当前activity的stop方法-证明通过AMS的检查了" class="headerlink" title="5. 打印结果(没有报错，打印了当前activity的stop方法,证明通过AMS的检查了)"></a>5. 打印结果(没有报错，打印了当前activity的stop方法,证明通过AMS的检查了)</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">com.dhcc.net.plug.HookUtil: Activity已经开始启动</span><br><span class="line">com.dhcc.net.plug.HookUtil: 小弟到此一游！！！</span><br></pre></td></tr></table></figure>
<h4 id="二、启动时替换成我们自己的Actvity"><a href="#二、启动时替换成我们自己的Actvity" class="headerlink" title="二、启动时替换成我们自己的Actvity"></a>二、启动时替换成我们自己的Actvity</h4><h5 id="1-当AMS加载activty完成以后，就要启动activity了，这个时候他是通过ActivityThread类中的Handler去处理的。我们首先看看Handler是怎么分发消息的（我们处理msg-callback，将优先级最大化）"><a href="#1-当AMS加载activty完成以后，就要启动activity了，这个时候他是通过ActivityThread类中的Handler去处理的。我们首先看看Handler是怎么分发消息的（我们处理msg-callback，将优先级最大化）" class="headerlink" title="1. 当AMS加载activty完成以后，就要启动activity了，这个时候他是通过ActivityThread类中的Handler去处理的。我们首先看看Handler是怎么分发消息的（我们处理msg.callback，将优先级最大化）"></a>1. 当AMS加载activty完成以后，就要启动activity了，这个时候他是通过ActivityThread类中的Handler去处理的。我们首先看看Handler是怎么分发消息的（我们处理msg.callback，将优先级最大化）</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">/**</span><br><span class="line"> * Handle system messages here.</span><br><span class="line"> */</span><br><span class="line"> public void dispatchMessage(Message msg) {</span><br><span class="line"> if (msg.callback != null) {</span><br><span class="line"> handleCallback(msg);</span><br><span class="line"> } else {</span><br><span class="line"> if (mCallback != null) {</span><br><span class="line"> if (mCallback.handleMessage(msg)) {</span><br><span class="line"> return;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> handleMessage(msg);</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<h5 id="2-替换成为自己的Activity"><a href="#2-替换成为自己的Activity" class="headerlink" title="2. 替换成为自己的Activity"></a>2. 替换成为自己的Activity</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br></pre></td><td class="code"><pre><span class="line">public void hookLaunchActivity() throws Exception{</span><br><span class="line"> // 3.4.1 获取ActivityThread实例</span><br><span class="line"> Class<?> atClass = Class.forName("android.app.ActivityThread");</span><br><span class="line"> Field scatField = atClass.getDeclaredField("sCurrentActivityThread");</span><br><span class="line"> scatField.setAccessible(true);</span><br><span class="line"> Object sCurrentActivityThread = scatField.get(null);</span><br><span class="line"> </span><br><span class="line"> </span><br><span class="line"> // 3.4.2 获取ActivityThread中的mH</span><br><span class="line"> Field mhField = atClass.getDeclaredField("mH");</span><br><span class="line"> mhField.setAccessible(true);</span><br><span class="line"> Object mHandler = mhField.get(sCurrentActivityThread);</span><br><span class="line"> </span><br><span class="line"> </span><br><span class="line"> // 3.4 设置当前对象（也就是ActivityThread）的mH的成员变量</span><br><span class="line"> Class<?> handlerClass = Class.forName("android.os.Handler");</span><br><span class="line"> Field mCallbackField = handlerClass.getDeclaredField("mCallback");</span><br><span class="line"> mCallbackField.setAccessible(true);</span><br><span class="line"> mCallbackField.set(mHandler,new HandlerCallBack());</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> </span><br><span class="line"> private class HandlerCallBack implements Handler.Callback{</span><br><span class="line"></span><br><span class="line"> @Override</span><br><span class="line"> public boolean handleMessage(Message msg) {</span><br><span class="line"> Log.e(TAG,"handleMessage");</span><br><span class="line"> // 每发一个消息都会走一次这个CallBack发放</span><br><span class="line"> if(msg.what == 100){</span><br><span class="line"> handleLaunchActivity(msg);</span><br><span class="line"> }</span><br><span class="line"> return false;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> /**</span><br><span class="line"> * 开始启动创建Activity拦截</span><br><span class="line"> * @param msg</span><br><span class="line"> */</span><br><span class="line"> private void handleLaunchActivity(Message msg) {</span><br><span class="line"> try {</span><br><span class="line"> Object record = msg.obj;</span><br><span class="line"> // 1.从record 获取过安检的Intent</span><br><span class="line"> Field intentField = record.getClass().getDeclaredField("intent");</span><br><span class="line"> intentField.setAccessible(true);</span><br><span class="line"> Intent proxyInent = (Intent) intentField.get(record);</span><br><span class="line"></span><br><span class="line"> // 2.从safeIntent中获取原来的originIntent</span><br><span class="line"> Intent realIntent = proxyInent.getParcelableExtra(EXTRA_ORIGIN_INTENT);</span><br><span class="line"></span><br><span class="line"> // 3.重新设置回去</span><br><span class="line"> if(realIntent != null){</span><br><span class="line"> Log.e(TAG,"启动我们自己的activity了");</span><br><span class="line"> intentField.set(record,realIntent);</span><br><span class="line"> }</span><br><span class="line"> }catch (Exception e){</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<h5 id="3-修改一下OnCreate方法"><a href="#3-修改一下OnCreate方法" class="headerlink" title="3. 修改一下OnCreate方法"></a>3. 修改一下OnCreate方法</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"> protected void onCreate(Bundle savedInstanceState) {</span><br><span class="line"> super.onCreate(savedInstanceState);</span><br><span class="line"> setContentView(R.layout.activity_main);</span><br><span class="line"></span><br><span class="line"> ButterKnife.bind(this);</span><br><span class="line"> mButton.setText("test");</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> //初始化插件</span><br><span class="line"> HookUtil hookUtil =new HookUtil(this, ProxyActivity.class);</span><br><span class="line"> try {</span><br><span class="line"> hookUtil.hookStartActivity();</span><br><span class="line"> hookUtil.hookLaunchActivity();</span><br><span class="line"> } catch (Exception e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="4-看看打印结果"><a href="#4-看看打印结果" class="headerlink" title="4. 看看打印结果"></a>4. 看看打印结果</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">com.dhcc.net.plug.HookUtil: Activity已经开始启动</span><br><span class="line">com.dhcc.net.plug.HookUtil: 小弟到此一游！！！</span><br><span class="line">com.dhcc.net.plug.HookUtil: 启动我们自己的activity了</span><br><span class="line">com.dhcc.net E/Main3Activity: 我是没有注册的Activity</span><br></pre></td></tr></table></figure>
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<time title="创建时间：2019-04-09 16:39:22 / 修改时间：21:13:31" itemprop="dateCreated datePublished" datetime="2019-04-09T16:39:22+08:00">2019-04-09</time>
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<h4 id="一、源码分析"><a href="#一、源码分析" class="headerlink" title="一、源码分析"></a>一、源码分析</h4><h5 id="1-一般调用"><a href="#1-一般调用" class="headerlink" title="1. 一般调用"></a>1. 一般调用</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">mHandler.sendEmptyMessage(100);</span><br></pre></td></tr></table></figure>
<h5 id="2-Handler-java"><a href="#2-Handler-java" class="headerlink" title="2. Handler.java"></a>2. Handler.java</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br></pre></td><td class="code"><pre><span class="line">public final boolean sendEmptyMessage(int what)</span><br><span class="line">{</span><br><span class="line"> return sendEmptyMessageDelayed(what, 0);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">public final boolean sendEmptyMessageDelayed(int what, long delayMillis) {</span><br><span class="line"> Message msg = Message.obtain();</span><br><span class="line"> msg.what = what;</span><br><span class="line"> return sendMessageDelayed(msg, delayMillis);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">public final boolean sendMessageDelayed(Message msg, long delayMillis)</span><br><span class="line"> {</span><br><span class="line"> if (delayMillis < 0) {</span><br><span class="line"> delayMillis = 0;</span><br><span class="line"> }</span><br><span class="line"> return sendMessageAtTime(msg, SystemClock.uptimeMillis() + delayMillis);</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line">public boolean sendMessageAtTime(Message msg, long uptimeMillis) {</span><br><span class="line"> MessageQueue queue = mQueue;</span><br><span class="line"> if (queue == null) {</span><br><span class="line"> RuntimeException e = new RuntimeException(</span><br><span class="line"> this + " sendMessageAtTime() called with no mQueue");</span><br><span class="line"> Log.w("Looper", e.getMessage(), e);</span><br><span class="line"> return false;</span><br><span class="line"> }</span><br><span class="line"> return enqueueMessage(queue, msg, uptimeMillis);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line">private boolean enqueueMessage(MessageQueue queue, Message msg, long uptimeMillis) {</span><br><span class="line"> msg.target = this;</span><br><span class="line"> if (mAsynchronous) {</span><br><span class="line"> msg.setAsynchronous(true);</span><br><span class="line"> }</span><br><span class="line"> return queue.enqueueMessage(msg, uptimeMillis);</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<h5 id="3-MessageQueue-java"><a href="#3-MessageQueue-java" class="headerlink" title="3. MessageQueue.java"></a>3. MessageQueue.java</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br></pre></td><td class="code"><pre><span class="line">boolean enqueueMessage(Message msg, long when) {</span><br><span class="line"> if (msg.target == null) {</span><br><span class="line"> throw new IllegalArgumentException("Message must have a target.");</span><br><span class="line"> }</span><br><span class="line"> if (msg.isInUse()) {</span><br><span class="line"> throw new IllegalStateException(msg + " This message is already in use.");</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> synchronized (this) {</span><br><span class="line"> if (mQuitting) {</span><br><span class="line"> IllegalStateException e = new IllegalStateException(</span><br><span class="line"> msg.target + " sending message to a Handler on a dead thread");</span><br><span class="line"> Log.w(TAG, e.getMessage(), e);</span><br><span class="line"> msg.recycle();</span><br><span class="line"> return false;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> msg.markInUse();</span><br><span class="line"> msg.when = when;</span><br><span class="line"> Message p = mMessages;</span><br><span class="line"> boolean needWake;</span><br><span class="line"> // 第一次添加数据到队列中，或者当前 msg 的时间小于 mMessages 的时间</span><br><span class="line"> if (p == null || when == 0 || when < p.when) {</span><br><span class="line"> // New head, wake up the event queue if blocked.</span><br><span class="line"> msg.next = p;</span><br><span class="line"> mMessages = msg;</span><br><span class="line"> needWake = mBlocked;</span><br><span class="line"> } else {</span><br><span class="line"> // Inserted within the middle of the queue. Usually we don't have to wake</span><br><span class="line"> // up the event queue unless there is a barrier at the head of the queue</span><br><span class="line"> // and the message is the earliest asynchronous message in the queue.</span><br><span class="line"> needWake = mBlocked && p.target == null && msg.isAsynchronous();</span><br><span class="line"> Message prev;</span><br><span class="line"> for (;;) {</span><br><span class="line"> prev = p;</span><br><span class="line"> p = p.next;</span><br><span class="line"> if (p == null || when < p.when) {</span><br><span class="line"> break;</span><br><span class="line"> }</span><br><span class="line"> if (needWake && p.isAsynchronous()) {</span><br><span class="line"> needWake = false;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> // 把当前 msg 插入到列表中</span><br><span class="line"> msg.next = p; // invariant: p == prev.next</span><br><span class="line"> prev.next = msg;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // We can assume mPtr != 0 because mQuitting is false.</span><br><span class="line"> if (needWake) {</span><br><span class="line"> nativeWake(mPtr);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> return true;</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<h5 id="4-把消息都存到队列里面去了，然后他们是怎么轮训的呢？（Looper-java）"><a href="#4-把消息都存到队列里面去了，然后他们是怎么轮训的呢？（Looper-java）" class="headerlink" title="4.把消息都存到队列里面去了，然后他们是怎么轮训的呢？（Looper.java）"></a>4.把消息都存到队列里面去了，然后他们是怎么轮训的呢？（Looper.java）</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br></pre></td><td class="code"><pre><span class="line"> /**</span><br><span class="line"> * Run the message queue in this thread. Be sure to call</span><br><span class="line"> * {@link #quit()} to end the loop.</span><br><span class="line">*/</span><br><span class="line">public static void loop() {</span><br><span class="line"> final Looper me = myLooper();</span><br><span class="line"> if (me == null) {</span><br><span class="line"> throw new RuntimeException("No Looper; Looper.prepare() wasn't called on this thread.");</span><br><span class="line"> }</span><br><span class="line"> final MessageQueue queue = me.mQueue;</span><br><span class="line"></span><br><span class="line"> // Make sure the identity of this thread is that of the local process,</span><br><span class="line"> // and keep track of what that identity token actually is.</span><br><span class="line"> Binder.clearCallingIdentity();</span><br><span class="line"> final long ident = Binder.clearCallingIdentity();</span><br><span class="line"></span><br><span class="line"> for (;;) {</span><br><span class="line"> // 不断的从消息队列里面取消息</span><br><span class="line"> Message msg = queue.next(); // might block</span><br><span class="line"> if (msg == null) {</span><br><span class="line"> // No message indicates that the message queue is quitting.</span><br><span class="line"> return;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // This must be in a local variable, in case a UI event sets the logger</span><br><span class="line"> Printer logging = me.mLogging;</span><br><span class="line"> if (logging != null) {</span><br><span class="line"> logging.println(">>>>> Dispatching to " + msg.target + " " +</span><br><span class="line"> msg.callback + ": " + msg.what);</span><br><span class="line"> }</span><br><span class="line"> // 通过 target 去 dispatchMessage 而 target 就是绑定的 Handler</span><br><span class="line"> msg.target.dispatchMessage(msg);</span><br><span class="line"></span><br><span class="line"> if (logging != null) {</span><br><span class="line"> logging.println("<<<<< Finished to " + msg.target + " " + msg.callback);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // Make sure that during the course of dispatching the</span><br><span class="line"> // identity of the thread wasn't corrupted.</span><br><span class="line"> final long newIdent = Binder.clearCallingIdentity();</span><br><span class="line"> if (ident != newIdent) {</span><br><span class="line"> Log.wtf(TAG, "Thread identity changed from 0x"</span><br><span class="line"> + Long.toHexString(ident) + " to 0x"</span><br><span class="line"> + Long.toHexString(newIdent) + " while dispatching to "</span><br><span class="line"> + msg.target.getClass().getName() + " "</span><br><span class="line"> + msg.callback + " what=" + msg.what);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> msg.recycleUnchecked();</span><br><span class="line"> }</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<h5 id="5-这个loop是什么时候调用的呢？我们看看ActivityThread的main方法（ActivityThread-java）"><a href="#5-这个loop是什么时候调用的呢？我们看看ActivityThread的main方法（ActivityThread-java）" class="headerlink" title="5. 这个loop是什么时候调用的呢？我们看看ActivityThread的main方法（ActivityThread.java）"></a>5. 这个loop是什么时候调用的呢？我们看看ActivityThread的main方法（ActivityThread.java）</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line">public static void main(String[] args) {</span><br><span class="line"> Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "ActivityThreadMain");</span><br><span class="line"> SamplingProfilerIntegration.start();</span><br><span class="line"></span><br><span class="line"> Process.setArgV0("<pre-initialized>");</span><br><span class="line"> // 初始化Looper</span><br><span class="line"> Looper.prepareMainLooper();</span><br><span class="line"></span><br><span class="line"> ActivityThread thread = new ActivityThread();</span><br><span class="line"> thread.attach(false);</span><br><span class="line"></span><br><span class="line"> if (sMainThreadHandler == null) {</span><br><span class="line"> sMainThreadHandler = thread.getHandler();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> if (false) {</span><br><span class="line"> Looper.myLooper().setMessageLogging(new</span><br><span class="line"> LogPrinter(Log.DEBUG, "ActivityThread"));</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // End of event ActivityThreadMain.</span><br><span class="line"> Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);</span><br><span class="line"> </span><br><span class="line"> // 开始轮训</span><br><span class="line"> Looper.loop();</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<h5 id="6-总结"><a href="#6-总结" class="headerlink" title="6. 总结"></a>6. 总结</h5><ul>
<li>handler.sendMessage 其实只是把我们的 Message 加入了消息队列，队列采用的是链表的方式，按照 when 也就是时间排序，然后再也没干其他；</li>
<li>Looper的loop一直轮训这个队列，这是一个死循环，然后调用message的target，就是我们写的Handler执行dispatchMessage。</li>
<li>当Laucher启动一个App的时候，首先会通过zygote Fork一个进程，然后进程会执行ActivityThread的main函数，在main函数里面初始化looper，执行loop。</li>
</ul>
<h4 id="二、自己手写"><a href="#二、自己手写" class="headerlink" title="二、自己手写"></a>二、自己手写</h4><h5 id="1-Handler"><a href="#1-Handler" class="headerlink" title="1. Handler"></a>1. Handler</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br></pre></td><td class="code"><pre><span class="line">public class Handler {</span><br><span class="line"> // 包含一个消息队列</span><br><span class="line"> MessageQueue mQueue;</span><br><span class="line"> </span><br><span class="line"> public Handler() {</span><br><span class="line"> //获取looper 轮训器。在Activity启动的时候创建</span><br><span class="line"> Looper looper = Looper.myLooper();</span><br><span class="line"> </span><br><span class="line"> if(looper == null){</span><br><span class="line"> throw new RuntimeException(</span><br><span class="line"> "Can't create handler inside thread that has not called Looper.prepare()");</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> mQueue= looper.mQueue;</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> public void sendMessage(Message message) {</span><br><span class="line"> sendMessageDelayed(message,0);</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> public final boolean sendMessageDelayed(Message msg, long delayMillis)</span><br><span class="line"> {</span><br><span class="line"> if (delayMillis < 0) {</span><br><span class="line"> delayMillis = 0;</span><br><span class="line"> }</span><br><span class="line"> return sendMessageAtTime(msg, System.currentTimeMillis() + delayMillis);</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> public boolean sendMessageAtTime(Message msg, long uptimeMillis) {</span><br><span class="line"> MessageQueue queue = mQueue;</span><br><span class="line"> return enqueueMessage(queue, msg, uptimeMillis);</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> private boolean enqueueMessage(MessageQueue queue, Message msg, long uptimeMillis) {</span><br><span class="line"> msg.target = this;</span><br><span class="line"> return queue.enqueueMessage(msg, uptimeMillis);</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> // 空方法并没具体的实现</span><br><span class="line"> public void handleMessage(Message msg) {</span><br><span class="line"> </span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="2-Looper"><a href="#2-Looper" class="headerlink" title="2. Looper"></a>2. Looper</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br></pre></td><td class="code"><pre><span class="line">public class Looper {</span><br><span class="line"> // sThreadLocal.get() will return null unless you've called prepare().</span><br><span class="line"> static final ThreadLocal<Looper> sThreadLocal = new ThreadLocal<Looper>();</span><br><span class="line"> </span><br><span class="line"> public static void prepare() {</span><br><span class="line"> sThreadLocal.set(new Looper());</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> MessageQueue mQueue;</span><br><span class="line"> </span><br><span class="line"> public Looper() {</span><br><span class="line"> mQueue = new MessageQueue();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> public static void loop() {</span><br><span class="line"> //无限轮训 获取队列里面的消息</span><br><span class="line"> Looper looper = myLooper();</span><br><span class="line"> for(;;){</span><br><span class="line"> MessageQueue queue = looper.mQueue;</span><br><span class="line"> </span><br><span class="line"> Message message = queue.next();</span><br><span class="line"> </span><br><span class="line"> if(message == null){</span><br><span class="line"> return;</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> message.target.handleMessage(message);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> static Looper myLooper() {</span><br><span class="line"> return sThreadLocal.get();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="3-MessageQueue"><a href="#3-MessageQueue" class="headerlink" title="3. MessageQueue"></a>3. MessageQueue</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br></pre></td><td class="code"><pre><span class="line">public class MessageQueue {</span><br><span class="line"> private Message mMessages;</span><br><span class="line"></span><br><span class="line"> // 按照时间排序插入</span><br><span class="line"> public boolean enqueueMessage(Message msg, long when) {</span><br><span class="line"> synchronized (this) {</span><br><span class="line"> msg.when = when;</span><br><span class="line"> Message p = mMessages;</span><br><span class="line"> //按照when 的时间进行排序插入</span><br><span class="line"> if (p == null || when == 0 || when < p.when) {</span><br><span class="line"> // New head, wake up the event queue if blocked.</span><br><span class="line"> msg.next = p;</span><br><span class="line"> mMessages = msg;</span><br><span class="line"> } else {</span><br><span class="line"> Message prev;</span><br><span class="line"> for (;;) {</span><br><span class="line"> prev = p;</span><br><span class="line"> p = p.next;</span><br><span class="line"> if (p == null || when < p.when) {</span><br><span class="line"> break;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> msg.next = p; // invariant: p == prev.next</span><br><span class="line"> prev.next = msg;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> return true;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // 无限轮训 获取下一个消息</span><br><span class="line"> public Message next() {</span><br><span class="line"> int pendingIdleHandlerCount = -1; // -1 only during first iteration</span><br><span class="line"> for (;;) {</span><br><span class="line"></span><br><span class="line"> synchronized (this) {</span><br><span class="line"> // Try to retrieve the next message. Return if found.</span><br><span class="line"> final long now = System.currentTimeMillis();</span><br><span class="line"> Message prevMsg = null;</span><br><span class="line"> Message msg = mMessages;</span><br><span class="line"> if (msg != null && msg.target == null) {</span><br><span class="line"> // Stalled by a barrier. Find the next asynchronous message</span><br><span class="line"> // in the queue.</span><br><span class="line"> do {</span><br><span class="line"> prevMsg = msg;</span><br><span class="line"> msg = msg.next;</span><br><span class="line"> } while (msg != null);</span><br><span class="line"> }</span><br><span class="line"> if (msg != null) {</span><br><span class="line"> if (now < msg.when) {</span><br><span class="line"> // Next message is not ready. Set a timeout to wake up</span><br><span class="line"> // when it is ready.</span><br><span class="line"> } else {</span><br><span class="line"> if (prevMsg != null) {</span><br><span class="line"> prevMsg.next = msg.next;</span><br><span class="line"> } else {</span><br><span class="line"> mMessages = msg.next;</span><br><span class="line"> }</span><br><span class="line"> msg.next = null;</span><br><span class="line"> return msg;</span><br><span class="line"> }</span><br><span class="line"> } else {</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> if (pendingIdleHandlerCount <= 0) {</span><br><span class="line"> continue;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="4-Message"><a href="#4-Message" class="headerlink" title="4. Message"></a>4. Message</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">public class Message {</span><br><span class="line"></span><br><span class="line"> public Object obj;</span><br><span class="line"> public Handler target;</span><br><span class="line"> public long when;</span><br><span class="line"> public Message next;</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="5-因为Looper是在主线程中执行的，我们来写一个ActivityThread"><a href="#5-因为Looper是在主线程中执行的，我们来写一个ActivityThread" class="headerlink" title="5. 因为Looper是在主线程中执行的，我们来写一个ActivityThread"></a>5. 因为Looper是在主线程中执行的，我们来写一个ActivityThread</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line">public class ActivityThread {</span><br><span class="line"> final H mH = new H();</span><br><span class="line"> </span><br><span class="line"> public void attach(boolean b) {</span><br><span class="line"> Activity mainActivity = new TestActivity();</span><br><span class="line"> mainActivity.onCreate();</span><br><span class="line"></span><br><span class="line"> // 通过 Handler 去执行Activity的生命周期</span><br><span class="line"> Message message = new Message();</span><br><span class="line"> message.obj = mainActivity;</span><br><span class="line"> mH.sendMessage(message);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> private class H extends Handler {</span><br><span class="line"> public void handleMessage(Message msg) {</span><br><span class="line"> Activity mainActivity = (Activity) msg.obj;</span><br><span class="line"> mainActivity.onResume();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="6-模拟Activity"><a href="#6-模拟Activity" class="headerlink" title="6. 模拟Activity"></a>6. 模拟Activity</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">public class Activity {</span><br><span class="line"></span><br><span class="line"> public void onCreate(){</span><br><span class="line"> </span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> public void onResume(){</span><br><span class="line"> </span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> public TextView findViewById(int id){</span><br><span class="line"> return new TextView();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="7-TestActivity"><a href="#7-TestActivity" class="headerlink" title="7. TestActivity"></a>7. TestActivity</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br></pre></td><td class="code"><pre><span class="line">/**</span><br><span class="line"> * @author 512573717@qq.com</span><br><span class="line"> * @created 2018/8/23 下午7:08.</span><br><span class="line"> */</span><br><span class="line">public class TestActivity extends Activity {</span><br><span class="line"> private static final String TAG = "TestActivity";</span><br><span class="line"> private TextView mHTextView;</span><br><span class="line"></span><br><span class="line"> private Handler mHHandler = new Handler() {</span><br><span class="line"></span><br><span class="line"> @Override</span><br><span class="line"> public void handleMessage(Message message) {</span><br><span class="line"> Log.e(TAG, "当前线程名称===="+Thread.currentThread().getName());</span><br><span class="line"> mHTextView.setText((CharSequence) message.obj);</span><br><span class="line"> }</span><br><span class="line"> };</span><br><span class="line"></span><br><span class="line"> @Override</span><br><span class="line"> public void onCreate() {</span><br><span class="line"> super.onCreate();</span><br><span class="line"></span><br><span class="line"> Log.e(TAG, "onCreate");</span><br><span class="line"> mHTextView = findViewById(0x111111);</span><br><span class="line"> new Thread(new Runnable() {</span><br><span class="line"> @Override</span><br><span class="line"> public void run() {</span><br><span class="line"></span><br><span class="line">// mHTextView.setText("I will be update !!!");</span><br><span class="line"></span><br><span class="line"> Log.e(TAG, "当前线程名称==="+Thread.currentThread().getName());</span><br><span class="line"></span><br><span class="line"> try {</span><br><span class="line"> Thread.sleep(100);</span><br><span class="line"> Message msg = new Message();</span><br><span class="line"> msg.obj = "I will be update !!!";</span><br><span class="line"> mHHandler.sendMessage(msg);</span><br><span class="line"> } catch (InterruptedException e) {</span><br><span class="line"> e.printStackTrace();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> ).start();</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> @Override</span><br><span class="line"> public void onResume() {</span><br><span class="line"> super.onResume();</span><br><span class="line"> Log.e(TAG, "onResume");</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="8-模拟UI控件TextView"><a href="#8-模拟UI控件TextView" class="headerlink" title="8. 模拟UI控件TextView"></a>8. 模拟UI控件TextView</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">public class TextView {</span><br><span class="line"> private Thread mThread;</span><br><span class="line"> public TextView(){</span><br><span class="line"> mThread = Thread.currentThread();</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> public void setText(CharSequence text){</span><br><span class="line"> checkThread();</span><br><span class="line"></span><br><span class="line"> System.out.println("更新UI成功："+text);</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> void checkThread() {</span><br><span class="line"> if (mThread != Thread.currentThread()) {</span><br><span class="line"> throw new RuntimeException(</span><br><span class="line"> "Only the original thread that created a view hierarchy can touch its views.");</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="9-Client"><a href="#9-Client" class="headerlink" title="9. Client"></a>9. Client</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">public class MainActivity extends AppCompatActivity {</span><br><span class="line"></span><br><span class="line"> @Override</span><br><span class="line"> protected void onCreate(Bundle savedInstanceState) {</span><br><span class="line"> super.onCreate(savedInstanceState);</span><br><span class="line"> setContentView(R.layout.activity_main);</span><br><span class="line"></span><br><span class="line"> Looper.prepare();</span><br><span class="line"></span><br><span class="line"> ActivityThread thread = new ActivityThread();</span><br><span class="line"> thread.attach(false);</span><br><span class="line"></span><br><span class="line"> Looper.loop();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h5 id="10-打印结果"><a href="#10-打印结果" class="headerlink" title="10 .打印结果"></a>10 .打印结果</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">1945-1945/? E/TestActivity: onCreate</span><br><span class="line">1945-1945/? E/TestActivity: onResume</span><br><span class="line">1945-1957/? E/TestActivity: 当前线程名称===Thread-161</span><br><span class="line">1945-1945/demo.dhcc.com.handlerdemo E/TestActivity: 当前线程名称====main</span><br><span class="line">1945-1945/demo.dhcc.com.handlerdemo I/System.out: 更新UI成功：I will be update !!!</span><br></pre></td></tr></table></figure>
<h4 id="三、面试相关问题"><a href="#三、面试相关问题" class="headerlink" title="三、面试相关问题"></a>三、面试相关问题</h4><h5 id="1-为什么不能再子线程里面创建Handler"><a href="#1-为什么不能再子线程里面创建Handler" class="headerlink" title="1. 为什么不能再子线程里面创建Handler"></a>1. 为什么不能再子线程里面创建Handler</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">new Thread(new Runnable() {</span><br><span class="line"> @Override</span><br><span class="line"> public void run() {</span><br><span class="line"></span><br><span class="line"> Handler handler=new Handler();</span><br><span class="line"> handler.sendMessage(Message.obtain());</span><br><span class="line"> }</span><br><span class="line"> }).start();</span><br><span class="line"> </span><br><span class="line">//</span><br></pre></td></tr></table></figure>
<p>  这个时候会报错“Can’t create handler inside thread that has not called Looper.prepare()”，查看源码发现。</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">public Handler(Callback callback, boolean async) {</span><br><span class="line"> if (FIND_POTENTIAL_LEAKS) {</span><br><span class="line"> final Class<? extends Handler> klass = getClass();</span><br><span class="line"> if ((klass.isAnonymousClass() || klass.isMemberClass() || klass.isLocalClass()) &&</span><br><span class="line"> (klass.getModifiers() & Modifier.STATIC) == 0) {</span><br><span class="line"> Log.w(TAG, "The following Handler class should be static or leaks might occur: " +</span><br><span class="line"> klass.getCanonicalName());</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> mLooper = Looper.myLooper();</span><br><span class="line"> if (mLooper == null) {</span><br><span class="line"> throw new RuntimeException(</span><br><span class="line"> "Can't create handler inside thread that has not called Looper.prepare()");</span><br><span class="line"> }</span><br><span class="line"> mQueue = mLooper.mQueue;</span><br><span class="line"> mCallback = callback;</span><br><span class="line"> mAsynchronous = async;</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<p>  修改代码</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">Looper.prepare();</span><br><span class="line">Handler handler=new Handler();</span><br><span class="line">handler.sendMessage(Message.obtain());</span><br><span class="line">Looper.loop();</span><br></pre></td></tr></table></figure>
<p>  为什么这样有可以</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">public static void prepare() {</span><br><span class="line"> prepare(true);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> private static void prepare(boolean quitAllowed) {</span><br><span class="line"> if (sThreadLocal.get() != null) {</span><br><span class="line"> throw new RuntimeException("Only one Looper may be created per thread");</span><br><span class="line"> }</span><br><span class="line"> sThreadLocal.set(new Looper(quitAllowed));</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> public void set(T value) {</span><br><span class="line"> Thread t = Thread.currentThread();</span><br><span class="line"> ThreadLocalMap map = getMap(t);</span><br><span class="line"> if (map != null)</span><br><span class="line"> map.set(this, value);</span><br><span class="line"> else</span><br><span class="line"> createMap(t, value);</span><br><span class="line"> }</span><br></pre></td></tr></table></figure>
<p>  为什么主线程的可以（ActivityThread.java）<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line">public static void main(String[] args) {</span><br><span class="line"> Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "ActivityThreadMain");</span><br><span class="line"> SamplingProfilerIntegration.start();</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"> Process.setArgV0("<pre-initialized>");</span><br><span class="line"></span><br><span class="line"> // 启动时已经创建了</span><br><span class="line"> Looper.prepareMainLooper();</span><br><span class="line"></span><br><span class="line"> ActivityThread thread = new ActivityThread();</span><br><span class="line"> thread.attach(false);</span><br><span class="line"></span><br><span class="line"> if (sMainThreadHandler == null) {</span><br><span class="line"> sMainThreadHandler = thread.getHandler();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> if (false) {</span><br><span class="line"> Looper.myLooper().setMessageLogging(new</span><br><span class="line"> LogPrinter(Log.DEBUG, "ActivityThread"));</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // End of event ActivityThreadMain.</span><br><span class="line"> Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);</span><br><span class="line"> Looper.loop();</span><br><span class="line"> </span><br><span class="line"> }</span><br></pre></td></tr></table></figure></p>
<h5 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h5><p>   一个Looper对应一个线程。存放在ThreadLocal里面。Looper必须创建了才有消息队列。如果没有消息队列Message就没地方存。所以必须先创建Looper。</p>
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<h4 id="引言"><a href="#引言" class="headerlink" title="引言"></a>引言</h4><p>  继续上一节的<a href="https://www.heyangjob.cn/2019/04/07/%E8%AE%BE%E8%AE%A1%E6%A8%A1%E5%BC%8F-%E5%A4%96%E8%A7%82%E6%A8%A1%E5%BC%8F%EF%BC%88%E5%8D%81%E5%9B%9B%EF%BC%89/" target="_blank" rel="noopener">外观模式</a>，我们在来说装饰模式。</p>
<h4 id="示例地址"><a href="#示例地址" class="headerlink" title="示例地址"></a>示例地址</h4><p>  <a href="https://github.com/heyangJob/Design-Pattern/tree/master/Wrapper" target="_blank" rel="noopener">Demo</a></p>
<h4 id="类图"><a href="#类图" class="headerlink" title="类图"></a>类图</h4><p><img src="https://note.youdao.com/yws/api/personal/file/WEB35902d03aeb7a8e9fa132d49e6df474b?method=download&shareKey=a0dbb7446606ea7113efa3deba0fa389" alt="image"></p>
<h4 id="定义"><a href="#定义" class="headerlink" title="定义"></a>定义</h4><p>  动态地给一个对象添加一些额外的职责。就增加功能来说，装饰模式相比生成子类更为灵活。</p>
<h4 id="使用场景"><a href="#使用场景" class="headerlink" title="使用场景"></a>使用场景</h4><p>  需要透明且动态地扩展的功能时。</p>
<h4 id="装饰模式角色介绍"><a href="#装饰模式角色介绍" class="headerlink" title="装饰模式角色介绍"></a>装饰模式角色介绍</h4><p>  1. Component：抽象组件，被装饰的原始对象。<br>  2. ConcreteComponent: 组件具体实现类。装饰的具体对象。<br>  3. Decorator:抽象的装饰者，用来装饰组件的。一般是为抽象类。如果装饰单一，该类可直接作为具体的装饰者。<br>  4. ConcreteDecoratorA：装饰者具体实现类。</p>
<h4 id="装饰模式示例"><a href="#装饰模式示例" class="headerlink" title="装饰模式示例"></a>装饰模式示例</h4><p>  最近帮别人买了手机。然后他自己贴了一个钢化膜，买了一个手机外壳，加上一个吊坠，格外的珍惜。不过比之前漂亮了不少。突然发现这是典型的装饰模式啊。</p>
<h6 id="1-定义手机接口"><a href="#1-定义手机接口" class="headerlink" title="1. 定义手机接口"></a>1. 定义手机接口</h6><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">/**</span><br><span class="line"> * 手机</span><br><span class="line"> *</span><br><span class="line"> * @author 512573717@qq.com</span><br><span class="line"> * @created 2018/7/25 下午5:30.</span><br><span class="line"> */</span><br><span class="line">public interface IPhone {</span><br><span class="line"> //装饰</span><br><span class="line"> void decorate();</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h6 id="2-实现手机接口（被装饰的对象-华为手机）"><a href="#2-实现手机接口（被装饰的对象-华为手机）" class="headerlink" title="2. 实现手机接口（被装饰的对象 华为手机）"></a>2. 实现手机接口（被装饰的对象 华为手机）</h6><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">/**</span><br><span class="line"> * 华为手机</span><br><span class="line"> *</span><br><span class="line"> * @author 512573717@qq.com</span><br><span class="line"> * @created 2018/7/26 下午1:59.</span><br><span class="line"> */</span><br><span class="line">public class HuaWeiPhone implements IPhone{</span><br><span class="line"> @Override</span><br><span class="line"> public void decorate() {</span><br><span class="line"> System.out.println("华为手机");</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h6 id="3-装饰者（外壳）"><a href="#3-装饰者（外壳）" class="headerlink" title="3. 装饰者（外壳）"></a>3. 装饰者（外壳）</h6><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">/**</span><br><span class="line"> * 外壳</span><br><span class="line"> *</span><br><span class="line"> * @author 512573717@qq.com</span><br><span class="line"> * @created 2018/7/26 下午2:01.</span><br><span class="line"> */</span><br><span class="line">public abstract class Shell implements IPhone {</span><br><span class="line"></span><br><span class="line"> private IPhone mHuaWeiPhone;</span><br><span class="line"></span><br><span class="line"> public Shell(IPhone huaWeiPhone) {</span><br><span class="line"> mHuaWeiPhone = huaWeiPhone;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> @Override</span><br><span class="line"> public void decorate() {</span><br><span class="line"> mHuaWeiPhone.decorate();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h6 id="4-粉红色的外壳加挂坠"><a href="#4-粉红色的外壳加挂坠" class="headerlink" title="4. 粉红色的外壳加挂坠"></a>4. 粉红色的外壳加挂坠</h6><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line">/**</span><br><span class="line"> * 红色的外壳</span><br><span class="line"> *</span><br><span class="line"> * @author 512573717@qq.com</span><br><span class="line"> * @created 2018/7/26 下午2:05.</span><br><span class="line"> */</span><br><span class="line">public class RedShell extends Shell {</span><br><span class="line"></span><br><span class="line"> public RedShell(IPhone huaWeiPhone) {</span><br><span class="line"> super(huaWeiPhone);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> public void shell() {</span><br><span class="line"> System.out.println("粉红色外壳");</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> public void pendant() {</span><br><span class="line"> System.out.println("小猪佩奇挂件");</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> @Override</span><br><span class="line"> public void decorate() {</span><br><span class="line"> super.decorate();</span><br><span class="line"> shell();</span><br><span class="line"> pendant();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h6 id="5-装饰者（贴膜）"><a href="#5-装饰者（贴膜）" class="headerlink" title="5. 装饰者（贴膜）"></a>5. 装饰者（贴膜）</h6><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">/**</span><br><span class="line"> * 手机贴膜</span><br><span class="line"> *</span><br><span class="line"> * @author 512573717@qq.com</span><br><span class="line"> * @created 2018/7/26 下午2:17.</span><br><span class="line"> */</span><br><span class="line">public abstract class Membrane implements IPhone {</span><br><span class="line"></span><br><span class="line"> private IPhone mHuaWeiPhone;</span><br><span class="line"></span><br><span class="line"> public Membrane(IPhone huaWeiPhone) {</span><br><span class="line"> mHuaWeiPhone = huaWeiPhone;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> @Override</span><br><span class="line"> public void decorate() {</span><br><span class="line"> mHuaWeiPhone.decorate();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h6 id="6-贴钢化膜"><a href="#6-贴钢化膜" class="headerlink" title="6. 贴钢化膜"></a>6. 贴钢化膜</h6><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line">/**</span><br><span class="line"> * 钢化膜</span><br><span class="line"> *</span><br><span class="line"> * @author 512573717@qq.com</span><br><span class="line"> * @created 2018/7/26 下午2:22.</span><br><span class="line"> */</span><br><span class="line">public class TemperingMembrane extends Membrane {</span><br><span class="line"></span><br><span class="line"> public TemperingMembrane(IPhone huaWeiPhone) {</span><br><span class="line"> super(huaWeiPhone);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> public void pasting() {</span><br><span class="line"> System.out.println("蓝光钢化膜");</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> @Override</span><br><span class="line"> public void decorate() {</span><br><span class="line"> super.decorate();</span><br><span class="line"> pasting();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h6 id="7-Client"><a href="#7-Client" class="headerlink" title="7. Client"></a>7. Client</h6><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">IPhone phone = new HuaWeiPhone();</span><br><span class="line"></span><br><span class="line">System.out.println("装饰外壳");</span><br><span class="line">RedShell redShell = new RedShell(phone);</span><br><span class="line">redShell.decorate();</span><br><span class="line"></span><br><span class="line">System.out.println("手机贴膜");</span><br><span class="line">TemperingMembrane temperingMembrane = new TemperingMembrane(redShell);</span><br><span class="line">temperingMembrane.decorate();</span><br></pre></td></tr></table></figure>
<h4 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h4><p>  装饰模式降低系统的耦合度，可以动态的增加或删除对象的职责，并使得需要装饰的具体构建类和具体装饰类可以独立变化，以便增加新的具体构建类和具体装饰类。 </p>
<p>  1. 优点：<br>    扩展对象功能，比继承灵活，不会导致类个数急剧增加<br>    可以对一个对象进行多次装饰，创造出不同行为的组合，得到功能更加强大的对象<br>    具体构建类和具体装饰类可以独立变化，用户可以根据需要自己增加新的具体构件子类和具体装饰子类</p>
<p>  2. 缺点：<br>    产生很多小对象。大量小对象占据内存，一定程度上影响性能<br>    装饰模式易于出错，调试排查比较麻烦</p>
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