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<p>在日常生活开发中，我们一般通过LayoutInflater来将xml文件加载到Activity当中，无论是在<code>setContentView(resId)</code>，或者在代码中直接通过<code>LayoutInflater.from(…)</code>等方法进行，还是换肤框架的基本思路，都是经由LayoutInflater来处理的，因此LayoutInflater在解析视图方面是扮演着一个非常重要的角色，那么既然那么重要，那就有必要学习一下了。</p>
<p>我们一般使用如下方式进行获取LayoutInflater:</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div><div class="line">4</div><div class="line">5</div><div class="line">6</div><div class="line">7</div><div class="line">8</div></pre></td><td class="code"><pre><div class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> LayoutInflater <span class="title">from</span><span class="params">(Context context)</span> </span>{</div><div class="line"> LayoutInflater LayoutInflater =</div><div class="line"> (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);</div><div class="line"> <span class="keyword">if</span> (LayoutInflater == <span class="keyword">null</span>) {</div><div class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> AssertionError(<span class="string">"LayoutInflater not found."</span>);</div><div class="line"> }</div><div class="line"> <span class="keyword">return</span> LayoutInflater;</div><div class="line"> }</div></pre></td></tr></table></figure>
<p>可以看到，其实在源码内部还是使用<code>context.getSystemService(Context.LAYOUT_INFLATER_SERVICE)</code>来进行的，那这里其实有个问题，一个Activity是对应一个LayoutInflater还是所有的Activity都是同一个LayoutInflater呢？一开始想到的是既然都是拿来解析xml文件布局，那么用一个实例肯定是最好的，不用分配多余的存储空间，但是其实一个Activity是对应一个LayoutInflater的，答案我们通过源码可以得到。</p>
<p>既然是通过getSystemService(…)获取到的，那么我们就需要找到这个方法的实现类，在Activity当中我们获取到的LayoutInflater来源于ContextThemeWrapper，而Activity是继承自ContextThemeWrapper，LayoutInflater的实现类为PhoneLayoutInflater：</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div><div class="line">4</div><div class="line">5</div><div class="line">6</div><div class="line">7</div><div class="line">8</div><div class="line">9</div><div class="line">10</div><div class="line">11</div><div class="line">12</div><div class="line">13</div><div class="line">14</div></pre></td><td class="code"><pre><div class="line"><span class="comment">//ContextThemeWrapper.java</span></div><div class="line"><span class="meta">@Override</span> <span class="function"><span class="keyword">public</span> Object <span class="title">getSystemService</span><span class="params">(String name)</span> </span>{</div><div class="line"> <span class="keyword">if</span> (LAYOUT_INFLATER_SERVICE.equals(name)) {</div><div class="line"> <span class="keyword">if</span> (mInflater == <span class="keyword">null</span>) {</div><div class="line"> mInflater = LayoutInflater.from(mBase).cloneInContext(<span class="keyword">this</span>);</div><div class="line"> }</div><div class="line"> <span class="keyword">return</span> mInflater;</div><div class="line"> }</div><div class="line"> <span class="keyword">return</span> mBase.getSystemService(name);</div><div class="line"> }</div><div class="line"><span class="comment">//PhoneLayoutInflater</span></div><div class="line"><span class="function"><span class="keyword">public</span> LayoutInflater <span class="title">cloneInContext</span><span class="params">(Context newContext)</span> </span>{</div><div class="line"> <span class="keyword">return</span> <span class="keyword">new</span> PhoneLayoutInflater(<span class="keyword">this</span>, newContext);</div><div class="line"> }</div></pre></td></tr></table></figure>
<p>最终设置的给LayoutInflater的Context是当前Activity的Context，那么其实也就意味着一个Activity是对应一个LayoutInflater，因为每个Activity的Context是不一样的所以对应生成的LayoutInflater也不一样。诶？！突然发现这个问题好弱智- -，推断一下就出来了，算了，就当理解一下获取到LayoutInflater的步骤吧。</p>
<p>上面扯了那么多，只是为了解决再看源码当时突然想到的问题：一个Activity是对应一个LayoutInflater还是所有的Activity都是同一个LayoutInflater呢。接下来就正式的开始深入的研究LayoutInflater的代码。当我们需要使用LayoutInflater去解析一个xml文件的时候，我们都会调用LayoutInflater.inflate(…)方法来进行解析最终获取到一个View，无论调用何种inflate(…)方法(前提是我们传入的是resource)，都会最后调用到底下的方法当中：</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div><div class="line">4</div><div class="line">5</div><div class="line">6</div><div class="line">7</div><div class="line">8</div><div class="line">9</div><div class="line">10</div></pre></td><td class="code"><pre><div class="line"><span class="function"><span class="keyword">public</span> View <span class="title">inflate</span><span class="params">(@LayoutRes <span class="keyword">int</span> resource, @Nullable ViewGroup root, <span class="keyword">boolean</span> attachToRoot)</span> </span>{</div><div class="line"> <span class="keyword">final</span> Resources res = getContext().getResources();</div><div class="line"> <span class="comment">//获取一个XmlResourceParser对象</span></div><div class="line"> <span class="keyword">final</span> XmlResourceParser parser = res.getLayout(resource);</div><div class="line"> <span class="keyword">try</span> {</div><div class="line"> <span class="keyword">return</span> inflate(parser, root, attachToRoot);</div><div class="line"> } <span class="keyword">finally</span> {</div><div class="line"> parser.close();</div><div class="line"> }</div><div class="line"> }</div></pre></td></tr></table></figure>
<p>XmlResourceParser的作用在于保存解析xml后的数据，然后就进入<code>inflate(parser, root, attachToRoot)</code>:</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div><div class="line">4</div><div class="line">5</div><div class="line">6</div><div class="line">7</div><div class="line">8</div><div class="line">9</div><div class="line">10</div><div class="line">11</div><div class="line">12</div><div class="line">13</div><div class="line">14</div><div class="line">15</div><div class="line">16</div><div class="line">17</div><div class="line">18</div><div class="line">19</div><div class="line">20</div><div class="line">21</div><div class="line">22</div><div class="line">23</div><div class="line">24</div><div class="line">25</div><div class="line">26</div><div class="line">27</div><div class="line">28</div><div class="line">29</div><div class="line">30</div><div class="line">31</div><div class="line">32</div><div class="line">33</div><div class="line">34</div><div class="line">35</div><div class="line">36</div><div 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class="line">75</div><div class="line">76</div><div class="line">77</div><div class="line">78</div><div class="line">79</div><div class="line">80</div></pre></td><td class="code"><pre><div class="line"><span class="function"><span class="keyword">public</span> View <span class="title">inflate</span><span class="params">(XmlPullParser parser, @Nullable ViewGroup root, <span class="keyword">boolean</span> attachToRoot)</span> </span>{</div><div class="line"> <span class="keyword">synchronized</span> (mConstructorArgs) {</div><div class="line"> ...</div><div class="line"> <span class="keyword">final</span> Context inflaterContext = mContext;</div><div class="line"> <span class="comment">//获取AttributeSet</span></div><div class="line"> <span class="keyword">final</span> AttributeSet attrs = Xml.asAttributeSet(parser);</div><div class="line"> Context lastContext = (Context) mConstructorArgs[<span class="number">0</span>];</div><div class="line"> mConstructorArgs[<span class="number">0</span>] = inflaterContext;</div><div class="line"> View result = root;</div><div class="line"></div><div class="line"> <span class="keyword">try</span> {</div><div class="line"> <span class="comment">// Look for the root node.</span></div><div class="line"> <span class="keyword">int</span> type;</div><div class="line"> <span class="keyword">while</span> ((type = parser.next()) != XmlPullParser.START_TAG &&</div><div class="line"> type != XmlPullParser.END_DOCUMENT) {</div><div class="line"> <span class="comment">// Empty</span></div><div class="line"> }</div><div class="line"> </div><div class="line"> <span class="keyword">if</span> (type != XmlPullParser.START_TAG) {</div><div class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> InflateException(parser.getPositionDescription()</div><div class="line"> + <span class="string">": No start tag found!"</span>);</div><div class="line"> }</div><div class="line"> <span class="comment">//找到第一个节点</span></div><div class="line"> <span class="keyword">final</span> String name = parser.getName();</div><div class="line"> <span class="comment">//是否是Merge标签</span></div><div class="line"> <span class="keyword">if</span> (TAG_MERGE.equals(name)) {</div><div class="line"> <span class="keyword">if</span> (root == <span class="keyword">null</span> || !attachToRoot) {</div><div class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> InflateException(<span class="string">"<merge /> can be used only with a valid "</span></div><div class="line"> + <span class="string">"ViewGroup root and attachToRoot=true"</span>);</div><div class="line"> }</div><div class="line"></div><div class="line"> rInflate(parser, root, inflaterContext, attrs, <span class="keyword">false</span>);</div><div class="line"> } <span class="keyword">else</span> {</div><div class="line"> <span class="comment">// Temp is the root view that was found in the xml</span></div><div class="line"> <span class="keyword">final</span> View temp = createViewFromTag(root, name, inflaterContext, attrs);</div><div class="line"> ViewGroup.LayoutParams params = <span class="keyword">null</span>;</div><div class="line"> <span class="keyword">if</span> (root != <span class="keyword">null</span>) {</div><div class="line"> <span class="comment">// Create layout params that match root, if supplied</span></div><div class="line"> params = root.generateLayoutParams(attrs);</div><div class="line"> <span class="keyword">if</span> (!attachToRoot) {</div><div class="line"> <span class="comment">// Set the layout params for temp if we are not</span></div><div class="line"> <span class="comment">// attaching. (If we are, we use addView, below)</span></div><div class="line"> temp.setLayoutParams(params);</div><div class="line"> }</div><div class="line"> }</div><div class="line"> <span class="comment">// Inflate all children under temp against its context.</span></div><div class="line"> rInflateChildren(parser, temp, attrs, <span class="keyword">true</span>);</div><div class="line"> <span class="comment">// We are supposed to attach all the views we found (int temp)</span></div><div class="line"> <span class="comment">// to root. Do that now.</span></div><div class="line"> <span class="keyword">if</span> (root != <span class="keyword">null</span> && attachToRoot) {</div><div class="line"> root.addView(temp, params);</div><div class="line"> }</div><div class="line"></div><div class="line"> <span class="comment">// Decide whether to return the root that was passed in or the</span></div><div class="line"> <span class="comment">// top view found in xml.</span></div><div class="line"> <span class="keyword">if</span> (root == <span class="keyword">null</span> || !attachToRoot) {</div><div class="line"> result = temp;</div><div class="line"> }</div><div class="line"> }</div><div class="line"></div><div class="line"> } <span class="keyword">catch</span> (XmlPullParserException e) {</div><div class="line"> <span class="keyword">final</span> InflateException ie = <span class="keyword">new</span> InflateException(e.getMessage(), e);</div><div class="line"> ie.setStackTrace(EMPTY_STACK_TRACE);</div><div class="line"> <span class="keyword">throw</span> ie;</div><div class="line"> } <span class="keyword">catch</span> (Exception e) {</div><div class="line"> <span class="keyword">final</span> InflateException ie = <span class="keyword">new</span> InflateException(parser.getPositionDescription()</div><div class="line"> + <span class="string">": "</span> + e.getMessage(), e);</div><div class="line"> ie.setStackTrace(EMPTY_STACK_TRACE);</div><div class="line"> <span class="keyword">throw</span> ie;</div><div class="line"> } <span class="keyword">finally</span> {</div><div class="line"> <span class="comment">// Don't retain static reference on context.</span></div><div class="line"> mConstructorArgs[<span class="number">0</span>] = lastContext;</div><div class="line"> mConstructorArgs[<span class="number">1</span>] = <span class="keyword">null</span>;</div><div class="line"></div><div class="line"> Trace.traceEnd(Trace.TRACE_TAG_VIEW);</div><div class="line"> }</div><div class="line"></div><div class="line"> <span class="keyword">return</span> result;</div><div class="line"> }</div><div class="line"> }</div></pre></td></tr></table></figure>
<p>该方法代码有点长，但也是我们今天要讲解的重点，主要逻辑就是递归解析布局文件并创建View树结构，然后返回该View树结构。该段代码中先通过Xml类的静态方法生成一个AttributeSet实例对象attrs，AttributeSet对象我们应该很熟悉，里边主要包含了相关属性的键值对。接下来就是通过parser解析器循环遍历查询布局文件的根节点，若没有查询到就会抛出异常。遍历完成之后获取到根节点名字存储在变量name中，然后进行判断。如果当前根节点标签名字是mege标签就走if()语句，否则进入else语句。由于我们在布局文件中没有使用merge标签，所以直接进入else语句中。进入else语句后，先定义值为null的临时变量temp，接着开始做判断，如果当前根节点标签名字为BlinkLayout就进入if语句，因为我们没有使用这个标签就进入else语句，在else语句中通过调用createViewFromTag()来创建一个View并赋值给temp。接下来又是条件判断，因为传递进来的root为空，所以跳过if(root != null)的判断语句，接着执行rInflate()方法(该方法是来循环渲染包含的所有的子视图的)。执行完成后返回temp的值。</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div><div class="line">4</div><div class="line">5</div><div class="line">6</div><div class="line">7</div><div class="line">8</div><div class="line">9</div><div class="line">10</div><div class="line">11</div><div class="line">12</div><div class="line">13</div><div class="line">14</div><div class="line">15</div><div class="line">16</div><div class="line">17</div><div class="line">18</div><div class="line">19</div><div class="line">20</div><div class="line">21</div><div class="line">22</div><div class="line">23</div><div class="line">24</div><div class="line">25</div><div class="line">26</div><div class="line">27</div><div class="line">28</div><div class="line">29</div><div class="line">30</div><div class="line">31</div><div class="line">32</div><div class="line">33</div><div class="line">34</div><div class="line">35</div><div class="line">36</div><div class="line">37</div><div class="line">38</div><div class="line">39</div><div class="line">40</div><div class="line">41</div><div class="line">42</div><div class="line">43</div><div class="line">44</div><div class="line">45</div><div class="line">46</div><div class="line">47</div><div class="line">48</div><div class="line">49</div><div class="line">50</div><div class="line">51</div><div class="line">52</div><div class="line">53</div><div class="line">54</div><div class="line">55</div><div class="line">56</div><div class="line">57</div><div class="line">58</div><div class="line">59</div><div class="line">60</div><div class="line">61</div><div class="line">62</div><div class="line">63</div><div class="line">64</div><div class="line">65</div></pre></td><td class="code"><pre><div class="line"><span class="function">View <span class="title">createViewFromTag</span><span class="params">(View parent, String name, Context context, AttributeSet attrs,<span class="keyword">boolean</span> ignoreThemeAttr)</span> </span>{</div><div class="line"> <span class="keyword">if</span> (name.equals(<span class="string">"view"</span>)) {</div><div class="line"> name = attrs.getAttributeValue(<span class="keyword">null</span>, <span class="string">"class"</span>);</div><div class="line"> }</div><div class="line"></div><div class="line"> <span class="comment">// Apply a theme wrapper, if allowed and one is specified.</span></div><div class="line"> <span class="keyword">if</span> (!ignoreThemeAttr) {</div><div class="line"> <span class="keyword">final</span> TypedArray ta = context.obtainStyledAttributes(attrs, ATTRS_THEME);</div><div class="line"> <span class="keyword">final</span> <span class="keyword">int</span> themeResId = ta.getResourceId(<span class="number">0</span>, <span class="number">0</span>);</div><div class="line"> <span class="keyword">if</span> (themeResId != <span class="number">0</span>) {</div><div class="line"> context = <span class="keyword">new</span> ContextThemeWrapper(context, themeResId);</div><div class="line"> }</div><div class="line"> ta.recycle();</div><div class="line"> }</div><div class="line"></div><div class="line"> <span class="keyword">if</span> (name.equals(TAG_1995)) {</div><div class="line"> <span class="comment">// Let's party like it's 1995!</span></div><div class="line"> <span class="keyword">return</span> <span class="keyword">new</span> BlinkLayout(context, attrs);</div><div class="line"> }</div><div class="line"></div><div class="line"> <span class="keyword">try</span> {</div><div class="line"> View view;</div><div class="line"> <span class="keyword">if</span> (mFactory2 != <span class="keyword">null</span>) {</div><div class="line"> view = mFactory2.onCreateView(parent, name, context, attrs);</div><div class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (mFactory != <span class="keyword">null</span>) {</div><div class="line"> view = mFactory.onCreateView(name, context, attrs);</div><div class="line"> } <span class="keyword">else</span> {</div><div class="line"> view = <span class="keyword">null</span>;</div><div class="line"> }</div><div class="line"></div><div class="line"> <span class="keyword">if</span> (view == <span class="keyword">null</span> && mPrivateFactory != <span class="keyword">null</span>) {</div><div class="line"> view = mPrivateFactory.onCreateView(parent, name, context, attrs);</div><div class="line"> }</div><div class="line"></div><div class="line"> <span class="keyword">if</span> (view == <span class="keyword">null</span>) {</div><div class="line"> <span class="keyword">final</span> Object lastContext = mConstructorArgs[<span class="number">0</span>];</div><div class="line"> mConstructorArgs[<span class="number">0</span>] = context;</div><div class="line"> <span class="keyword">try</span> {</div><div class="line"> <span class="keyword">if</span> (-<span class="number">1</span> == name.indexOf(<span class="string">'.'</span>)) {</div><div class="line"> view = onCreateView(parent, name, attrs);</div><div class="line"> } <span class="keyword">else</span> {</div><div class="line"> view = createView(name, <span class="keyword">null</span>, attrs);</div><div class="line"> }</div><div class="line"> } <span class="keyword">finally</span> {</div><div class="line"> mConstructorArgs[<span class="number">0</span>] = lastContext;</div><div class="line"> }</div><div class="line"> }</div><div class="line"></div><div class="line"> <span class="keyword">return</span> view;</div><div class="line"> } <span class="keyword">catch</span> (InflateException e) {</div><div class="line"> <span class="keyword">throw</span> e;</div><div class="line"></div><div class="line"> } <span class="keyword">catch</span> (ClassNotFoundException e) {</div><div class="line"> <span class="keyword">final</span> InflateException ie = <span class="keyword">new</span> InflateException(attrs.getPositionDescription()</div><div class="line"> + <span class="string">": Error inflating class "</span> + name, e);</div><div class="line"> ie.setStackTrace(EMPTY_STACK_TRACE);</div><div class="line"> <span class="keyword">throw</span> ie;</div><div class="line"></div><div class="line"> } <span class="keyword">catch</span> (Exception e) {</div><div class="line"> <span class="keyword">final</span> InflateException ie = <span class="keyword">new</span> InflateException(attrs.getPositionDescription()</div><div class="line"> + <span class="string">": Error inflating class "</span> + name, e);</div><div class="line"> ie.setStackTrace(EMPTY_STACK_TRACE);</div><div class="line"> <span class="keyword">throw</span> ie;</div><div class="line"> }</div><div class="line"> }</div></pre></td></tr></table></figure>
<p>方法createViewFromTag()主要流程就是通过标签名name来创建相应View实例对象并返回。在该方法中首先根据Factory实例对象来创建View，如果创建成功就直接返回，否则执行系统默认创建View流程。这里需要强调一点，LayoutInflater内部定义了一个boolean类型的mFactorySet开关，其值默认值为false，当我们调用过setFactory()或者是setFactory2()后mFactorySet为true，若我们再次调用这俩方法时会抛出异常，也就是说每一个LayoutInflater实例对象只能赋值一次Factory，若再想赋成其他值只能通过反射先把mFactorySet的值置为false防止抛异常。系统默认创建View流程是先通过判断标签名称中有没有包含”.”，如果没有包含就把标签名添加前缀”android.view.”，最终调用LayoutInflater的createView()方法，注意该方法是public并且是final类型的，是系统默认的创建View的方式，创建完成之后返回该view。</p>
<p>到这里我们已经清楚了LayoutInflater根据xml布局文件来渲染View视图的主要流程：先是通过布局文件的资源ID创建一个XmlResourceParser解析器对象parser，再是利用parser递归解析xml布局文件，然后根据解析出的标签名来创建相关View，最终返回层级视图View。如果LayoutInflater中设置了Factory，那么在创建每一个View时都会调用该Factory的onCreateView()方法，这个方法就是我们的入口点，如果想在每一个View创建之前做点处理，只需要在Factory的onCreateView()方法中做相关逻辑操作</p>
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<p>公司项目是基于插件进行开发的，在开发初期，由于时间成本以及插件框架不完善，所以为了避坑(主要来源于插件)，项目中大量利用了<code>Fragment</code>作为核心的展示视图，因此趁这段比较清闲的时间整理学习一下<code>Fragment</code>。</p>
<p>注：本文基于4.4源码</p>
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<p>日常开发中我们接触到的主要是View以及Activity，并且在此基础上开发，但是其实View跟Window是离不开的，所以本文旨在理清View,Window以及Activity之间的关系。</p>
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深入理解计算机系统第一章
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2017-03-04
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<h3>hello文件的周期过程</h3>
<p>hello.c</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div><div class="line">4</div></pre></td><td class="code"><pre><div class="line"><span class="meta">#<span class="meta-keyword">include</span> <span class="meta-string"><stdio.h></span></span></div><div class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span></span>{</div><div class="line"> <span class="built_in">printf</span>(<span class="string">"hello ,world\n"</span>);</div><div class="line">}</div></pre></td></tr></table></figure>
<p>hello文件的生命周期：创建->系统上运行->输出消息->终止</p>
<p>hello文件的生命周期由一个源文件开始，我们利用编辑器创建并且保存，这就是一个以.c结尾的文本文件，源程序实际上是由值0到1组成的位(bit)序列，8个位被组织成一组，称为字节。</p>
<p>hello.c以字节序列的方式存储在文件当中，每个字节都由一个整数值进行对应，即ASCII码来对应。</p>
<p>hello程序的生命周期从一个C语言开始，为了在系统上运行hello.c,每条C语言语句都会被转化成低级机器语言，然后这些指令会按照一种<strong>可执行目标程序</strong>的格式打包，以<strong>二进制磁盘文件</strong>的形式存放起来。<strong>目标程序也称为可执行文件</strong></p>
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<p>1.公司需求需要在RecycerView滑动的时候每一个item在可见度>=50%时上报数据，一般的RecyclerView.OnScrollListener中我们做处理，如果自己去计算item的展示可见度那是很麻烦的，解决思路如下:</p>
<p>重点代码:<strong>view.getGlobalVisibleRect()</strong>，getGlobalVisibleRect方法的作用是获取视图在屏幕坐标中的可视区域，那只要在代码OnScrollListener中加入判断即可：</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><div class="line">1</div><div class="line">2</div><div class="line">3</div><div class="line">4</div><div class="line">5</div><div class="line">6</div><div class="line">7</div><div class="line">8</div><div class="line">9</div><div class="line">10</div><div class="line">11</div><div class="line">12</div><div class="line">13</div><div class="line">14</div><div class="line">15</div><div class="line">16</div><div class="line">17</div><div class="line">18</div></pre></td><td class="code"><pre><div class="line"><span class="keyword">private</span> RecyclerView.OnScrollListener mOnScrollListener = <span class="keyword">new</span> RecyclerView.OnScrollListener() {</div><div class="line"> <span class="meta">@Override</span></div><div class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">onScrolled</span><span class="params">(RecyclerView recyclerView, <span class="keyword">int</span> dx, <span class="keyword">int</span> dy)</span> </span>{</div><div class="line"> <span class="keyword">super</span>.onScrolled(recyclerView, dx, dy);</div><div class="line"> <span class="keyword">int</span> lastVisbile = mLayoutManager.findLastVisibleItemPosition();</div><div class="line"> mLayoutManager.findFirstVisibleItemPosition();</div><div class="line"> <span class="comment">// 只有广告才需要50%上报</span></div><div class="line"> <span class="keyword">if</span> (mAdapter.getItemViewType(lastVisbile) != STYLE_CONTENT_BIG_IMG)</div><div class="line"> <span class="keyword">return</span>;</div><div class="line"> View view = mLayoutManager.findViewByPosition(lastVisbile);</div><div class="line"> Rect rect = <span class="keyword">new</span> Rect();</div><div class="line"> view.getGlobalVisibleRect(rect);</div><div class="line"> <span class="keyword">int</span> currentHeight = view.getHeight();</div><div class="line"> <span class="keyword">if</span> (rect.bottom - rect.top >= currentHeight / <span class="number">2</span>) {</div><div class="line"> Log.e(<span class="string">"zzzzzz"</span>, <span class="string">"曝光了---->"</span> + lastVisbile);</div><div class="line"> }</div><div class="line"> }</div><div class="line"> };</div></pre></td></tr></table></figure>
<p>实现的代码如上所示。</p>
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