在Android开发中我们经常会遇到展示列表的情况，在早期版本系统提供了ListView、GirdView供我们使用，今天来向大家介绍另外一个可以集ListView、GirdView和瀑布流与一身的强大控件RecyclerView。
下面我们先来看一下效果图：
RecyclerView是新增控件，使用前需要首先在build.gradle中添加support依赖库中，
dependencies {
compile fileTree(include: ['*.jar'], dir: 'libs')
testCompile 'junit:junit:4.12'
compile 'com.android.support:appcompat-v7:25.1.1'
compile 'com.android.support:recyclerview-v7:25.1.1'
}
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然后我们定义activity_main.xml文件，使用RedioGroup中的三个RadioButton切换三个Fragment来分别展示RecyclerView的ListView、GirdView和瀑布流三种模式。
<RadioGroup android:id="@+id/radioGroup" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal" android:padding="10dp"> <RadioButton android:id="@+id/listView" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="ListView" /> <RadioButton android:id="@+id/girdView" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="GirdView" /> <RadioButton android:id="@+id/wallFalls" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="WallFalls" /> </RadioGroup> <FrameLayout android:id="@+id/frameLayout" android:layout_width="match_parent" android:layout_height="match_parent" /> -
MainActivity.java代码实现三种模式的切换
public class MainActivity extends AppCompatActivity implements RadioGroup.OnCheckedChangeListener {
private FragmentManager fragmentManager; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); RadioGroup radioGroup = $(R.id.radioGroup); radioGroup.setOnCheckedChangeListener(this); fragmentManager = getSupportFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction(); fragmentTransaction.replace(R.id.frameLayout, new ListViewFragment()).commit(); radioGroup.check(R.id.listView); } protected <T extends View> T $(int id) { //return返回view时,加上泛型T return (T) findViewById(id); } @Override public void onCheckedChanged(RadioGroup radioGroup, int i) { switch (i) { case R.id.listView: fragmentManager.beginTransaction().replace(R.id.frameLayout, new ListViewFragment()).commit(); break; case R.id.girdView: fragmentManager.beginTransaction().replace(R.id.frameLayout, new GirdFragment()).commit(); break; case R.id.wallFalls: fragmentManager.beginTransaction().replace(R.id.frameLayout, new WaterFallsFragment()).commit(); break; default: break; } }}
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定义抽象类BaseFragment加载定义有RecyclerView控件的布局，要展示的三种模式的Fragment都要继承BaseFragment类并统一实现其中的抽象方法为控件添加Data数据
public abstract class BaseFragment extends Fragment {
protected RecyclerView recyclerView; @Override public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { View view = inflater.inflate(R.layout.fragment, null); recyclerView = (RecyclerView) view.findViewById(R.id.recyclerView); initAdapter(); return view; } public abstract void initAdapter(); protected List<String> getData() { List<String> list = new ArrayList<String>(); String[] data = Constant.data; for (int i = 0; i < 50; i++) { int random = new Random().nextInt(data.length); list.add(data[random]); } return list; } protected List<String> getWallFallsData() { List<String> list = new ArrayList<String>(); String[] data = Constant.data; StringBuilder builder; for (int i = 0; i < 50; i++) { builder = new StringBuilder(); int random = new Random().nextInt(data.length); for (int j = 0; j < new Random().nextInt(15)+5; j++) { builder.append(data[random] + "\n"); } list.add(builder.toString()); } return list; }}
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定义有RecyclerView的fragment.xml布局
<android.support.v7.widget.RecyclerView android:id="@+id/recyclerView" android:layout_width="match_parent" android:layout_height="wrap_content" />
RecyclerView可以通过设置setLayoutManager实现三种不同的展示形式，可设置为LinearLayoutManager(ListView形式)，GridLayoutManager(GirdView形式)，StaggeredGridLayoutManager(瀑布流形式)；每一种LayoutManager又可以通过设置setOrientation来设置是横向滑动还是垂直滑动
public class ListViewFragment extends BaseFragment {
@Override
public void initAdapter() {
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
//LinearLayoutManager.VERTICAL 垂直滑动，LinearLayoutManager.HORIZONTAL 水平滑动
linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
//也可在创建LinearLayoutManager的时候直接设置滑动方向,最后一个参数 reverseLayout表示是否逆序排列展示
//LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.HORIZONTAL, false);
//设置RecyclerView的展示模式
recyclerView.setLayoutManager(linearLayoutManager);
MyAdapter myAdapter = new MyAdapter(getActivity(), getData());
recyclerView.setAdapter(myAdapter);
myAdapter.setOnItemClickListener(new MyAdapter.OnItemClickLitener() {
@Override
public void onItemClick(View view, int position) {
Toast.makeText(getActivity(), "点击了Item：" + position, Toast.LENGTH_SHORT).show();
}
});
}
}
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新建MyAdapter类并在其中创建MyViewHolder继承ViewHolder，然后再将MyAdapte继承RecyclerView.Adapte并设置泛型为MyAdapter中的MyViewHolder。RecyclerView中没有实现回调，所以最后要自己手动实现回调方法。
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> { private Context context; private List list; private OnItemClickLitener onItemClickLitener;
public MyAdapter(Context context, List<String> list) { this.context = context; this.list = list; } @Override public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View view = LayoutInflater.from(context).inflate(R.layout.item_list_gird, parent, false); MyViewHolder holder = new MyViewHolder(view); return holder; } @Override public void onBindViewHolder(final MyViewHolder holder, int position) { holder.textView.setText(list.get(position)); holder.itemView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { int position = holder.getAdapterPosition(); onItemClickLitener.onItemClick(holder.itemView, position); } }); holder.textView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { int position = holder.getAdapterPosition(); Toast.makeText(context, "点击了TextView：" + position, Toast.LENGTH_SHORT).show(); } }); } @Override public int getItemCount() { return list.size(); } class MyViewHolder extends ViewHolder { private TextView textView; public MyViewHolder(View view) { super(view); //这个view就是Item的View textView = (TextView) view.findViewById(R.id.textView); } } public interface OnItemClickLitener { void onItemClick(View view, int position); } /** * 点击Item回调 * * @param onItemClickLitener */ public void setOnItemClickListener(OnItemClickLitener onItemClickLitener) { this.onItemClickLitener = onItemClickLitener; }}
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Item的布局item_list_gird.xml
<TextView android:id="@+id/textView" android:layout_width="wrap_content" android:layout_height="100dp" android:layout_gravity="center" android:gravity="center" android:text="java" />
public class GirdFragment extends BaseFragment {
@Override
public void initAdapter() {
GridLayoutManager gridLayoutManager = new GridLayoutManager(getActivity(),4);
//LinearLayoutManager.VERTICAL 垂直滑动，LinearLayoutManager.HORIZONTAL 水平滑动
gridLayoutManager.setOrientation(GridLayoutManager.VERTICAL);
//也可在创建GridLayoutManager的时候直接设置滑动方向,最后一个参数 reverseLayout表示是否逆序排列展示
// GridLayoutManager gridLayoutManager = new GridLayoutManager(getActivity(),4, GridLayoutManager.VERTICAL, false);
recyclerView.setLayoutManager(gridLayoutManager);
MyAdapter myAdapter = new MyAdapter(getActivity(), getData());
recyclerView.setAdapter(myAdapter);
myAdapter.setOnItemClickListener(new MyAdapter.OnItemClickLitener() {
@Override
public void onItemClick(View view, int position) {
Toast.makeText(getActivity(), "点击了Item：" + position, Toast.LENGTH_SHORT).show();
}
});
}
}
public class WaterFallsFragment extends BaseFragment {
@Override
public void initAdapter() {
StaggeredGridLayoutManager staggeredGridLayoutManager = new StaggeredGridLayoutManager(4, StaggeredGridLayoutManager.VERTICAL);
//LinearLayoutManager.VERTICAL 垂直滑动，LinearLayoutManager.HORIZONTAL 水平滑动
staggeredGridLayoutManager.setOrientation(StaggeredGridLayoutManager.VERTICAL);
recyclerView.setLayoutManager(staggeredGridLayoutManager);
WallFallsAdapter wallFallsAdapter = new WallFallsAdapter(getActivity(), getWallFallsData());
recyclerView.setAdapter(wallFallsAdapter);
wallFallsAdapter.setOnItemClickListener(new WallFallsAdapter.OnItemClickLitener() {
@Override
public void onItemClick(View view, int position) {
Toast.makeText(getActivity(), "点击了Item：" + position, Toast.LENGTH_SHORT).show();
}
});
}
}
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瀑布流Item布局item_wallfalls.xml，注意与前面的不同
<TextView android:id="@+id/textView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:gravity="center" android:text="Java" />
OK今天就到这里，这只是RecyclerView很基础的用法，RecyclerView控件功能非常强大后面我们将继续学习RecyclerView的高级用法。