RecyclerViews使用基础指南

RecyclerView

相关引用：
1. 《第一行代码 第二版》

2. https://www.jianshu.com/p/f86f59dccaef

3. https://www.jianshu.com/p/991062d964cf

对比ListView

拓展性更好、添加动画效果更加方便（自带ItemAnimation）、性能更好（ ListView继承自：AbsListView。(GirdView也是)， RecyclerView直接继承了ViewGroup，从封装的层次上得出了为什么RecyclerView性能比ListView更好的原因， 因为封装的层次越高，查询执行的速度相对较慢），更加灵活

基本使用步骤

1. moudle下的build.gradle添加依赖

   dependencies{
       compile fileTree(dir: 'libs',include: ['*.jar'])
       compile 'com.android.support:appcompat-v7:24.2.1'
       compile 'com.android.support:recyclerview-v7:24.2.1'
       testCompile 'junit:junit:4.12'
   }   
   

2. 在布局文件中添加该组件

   由于RecyclerView不是内置在SDK中，所以要把完整的包路径写出来。

3. 创建适配器

   public class MyRecyclerViewAdapter extends RecyclerView.Adapter {
       private final LayoutInflater mLayoutInflater;
       private final Context mContext;
       private String[] mTitles;
   
       // 传递数据源
       public MyRecyclerViewAdapter(Context context,String[] strs) {
           mTitles = strs;
           mContext = context;
           mLayoutInflater = LayoutInflater.from(context);
       }
   
       // 用于创建ViewHolder实例，在这个方法中将item的布局加载出来
       @Override
       public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {// 第二个参数就是View的类型，实现多布局关键
           return new ViewHolder(mLayoutInflater.inflate(R.layout.item_text, parent, false));
       }
   
       // 对每个item进行赋值，会在每个子项被滚动到屏幕内的时候执行
       @Override
       public void onBindViewHolder(ViewHolder holder, int position) {
           String str = mTitles[position];
           holder.mTextView.setText(str);
       }
   
       // 告诉RecyclerView有多少子项
       @Override
       public int getItemCount() {
           return mTitles == null ? 0 : mTitles.length;
       }
   
       public static class ViewHolder extends RecyclerView.ViewHolder {
           TextView mTextView;
   
           ViewHolder(View view) {
               super(view);
               mTextView = (TextView)view.findViewById(R.id.tv_title);
           }
       }
   }
   

4. 在Acvitiy中设置

   public class MainActivity extends ActionBarActivity {
       private RecyclerView mRecyclerView;
       private String[] mTitles;
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
           initData();
           mRecyclerView = (RecyclerView)findViewById(R.id.recyclerView);
           mRecyclerView.setLayoutManager(new LinearLayoutManager(this));//这里用线性显示 类似于listview
   //        mRecyclerView.setLayoutManager(new GridLayoutManager(this, 2));//这里用线性宫格显示 类似于grid view
   //        mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(2, OrientationHelper.VERTICAL));//这里用线性宫格显示 类似于瀑布流
           mRecyclerView.setAdapter(new NormalRecyclerViewAdapter(this,mTitles));
       }
   
       private void initData() {
           //to do sth here
       }
   }
   

5. 设置点击事件

   其实ListView的setOnItemClickListener()注册的是子项的点击事件，如果想点击的是子项里面具体控件的事件，那就比较麻烦了。居以此，RecyclerView的点击事件是由具体的View去注册

   public class MyRecyclerViewAdapter extends RecyclerView.Adapter {
       private final LayoutInflater mLayoutInflater;
       private final Context mContext;
       private String[] mTitles;
   
       // 传递数据源
       public MyRecyclerViewAdapter(Context context,String[] strs) {
           mTitles = strs;
           mContext = context;
           mLayoutInflater = LayoutInflater.from(context);
       }
   
       // 用于创建ViewHolder实例，在这个方法中将item的布局加载出来
       @Override
       public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
           View view = mLayoutInflater.inflate(R.layout.item_text, parent, false);
           final ViewHolder holder = new ViewHolder(view);
           holder.mRootView.setOnClickListener(new OnClickListener(){
               @override
               public void onClick(View v){
                   //to do sth here
               }
           });
           holder.mTextView.setOnClickListener(new OnClickListener(){
               @override
               public void onClick(View v){
                   //to do sth here
               }
           });
           return holder;
       }
   
       // 对每个item进行赋值，会在每个子项被滚动到屏幕内的时候执行
       @Override
       public void onBindViewHolder(ViewHolder holder, int position) {
           String str = mTitles[position];
           holder.mTextView.setText(str);
       }
   
       // 告诉RecyclerView有多少子项
       @Override
       public int getItemCount() {
           return mTitles == null ? 0 : mTitles.length;
       }
   
       public static class ViewHolder extends RecyclerView.ViewHolder {
           View mRootView;
           TextView mTextView;
   
           ViewHolder(View view) {
               super(view);
               mRootView = view;
               mTextView = (TextView)view.findViewById(R.id.tv_title);
           }
       }
   }
   

多Item布局实现(MultipleItem)

我们知道，在ListView中设置多种布局的关键就是getItemViewType()与getViewTypeCount()，在RecyclerView中，只有getItemViewType()，其用法也与ListView一致。并且onCreateViewHolder()的第二个参数int viewType就是getItemViewType()的返回值。思路如下：

• 定义不同的viewType常量(非必须) 。

• 在getItemViewType方法中根据position来返回不同的viewType 。

• 根据getItemViewType方法返回的不同的viewType在onCreateViewHolder创建不同的ViewHolder。

• onBindViewHolder方法里面用instanceof判断不同的ViewHolder来做不通的赋值处理。

• 注意getItemCount的返回值

  public class ViewTypeActivity extends AppCompatActivity {
      private RecyclerView mRecyclerView;
      private List mDatas;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          initData();
          setContentView(R.layout.activity_water_full);
          mRecyclerView = (RecyclerView) findViewById(R.id.id_recyclerview);
          mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
          mRecyclerView.addItemDecoration(new SpacesItemDecoration(12));
          mRecyclerView.setAdapter(new ViewTypeAdapter());
      }
  
      private void initData() {
          mDatas = new ArrayList();
          for (int i = 0; i < 24; i++) {
              mDatas.add("位置是" + i);
          }
      }
  
      class ViewTypeAdapter extends RecyclerView.Adapter{
  
          public static final int ONE_ITEM = 1;
          public static final int TWO_ITEM = 2;
  
          @Override
          public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
              LayoutInflater mInflater = LayoutInflater.from(ViewTypeActivity.this);
              RecyclerView.ViewHolder holder = null;
              if(ONE_ITEM == viewType){
                  View v = mInflater.inflate(R.layout.item_linear,parent,false);
                  holder = new OneViewHolder(v);
              }else{
                  View v = mInflater.inflate(R.layout.item_two,parent,false);
                  holder = new TwoViewHolder(v);
              }
              return holder;
          }
  
          @Override
          public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
              if(holder instanceof OneViewHolder){
                  ((OneViewHolder) holder).tv.setText(mDatas.get(position));
              }else {
                  ((TwoViewHolder) holder).tv1.setText(mDatas.get(position));
                  ((TwoViewHolder) holder).tv2.setText(mDatas.get(position));
              }
          }
  
          @Override
          public int getItemViewType(int position) {
              if(position % 3 == 0){
                  return TWO_ITEM;
              }else{
                  return ONE_ITEM;
              }
          }
  
          @Override
          public int getItemCount() {
              return mDatas.size();
          }
  
          class OneViewHolder extends RecyclerView.ViewHolder{
              TextView tv;
              public OneViewHolder(View itemView) {
                  super(itemView);
                  tv = (TextView) itemView.findViewById(R.id.adapter_linear_text);
              }
          }
  
          class TwoViewHolder extends RecyclerView.ViewHolder{
              TextView tv1,tv2;
              public TwoViewHolder(View itemView) {
                  super(itemView);
                  tv1 = (TextView) itemView.findViewById(R.id.adapter_two_1);
                  tv2 = (TextView) itemView.findViewById(R.id.adapter_two_2);
              }
          }
      }
  }
  
  作者：丿歌吟有梦
  链接：https://www.jianshu.com/p/f86f59dccaef
  來源：简书
  简书著作权归作者所有，任何形式的转载都请联系作者获得授权并注明出处。
  

当RecyclerView为LinearLayoutManager，我们可以通过viewType给RecyclerView来设置Header和Footer，但是当布局管理器为GridLayoutManager和StaggeredGridLayoutManager时就要不能这样去做了。
如何去加我会放在后面去写:

    public static final int HEADER = 1;
            public static final int FOOTER = 2;
            public static final int ITEM = 3;
            @Override
            public int getItemViewType(int position) {
                if(position == 0){
                    return HEADER;
                }else if(position == getItemCount() -1){
                    return FOOTER;
                }else{
                    return ITEM;
                }
            }

            @Override
            public int getItemCount() {
                return mDatas.size() + 2;//Header和Footer
            }

    作者：丿歌吟有梦
    链接：https://www.jianshu.com/p/f86f59dccaef
    來源：简书
    简书著作权归作者所有，任何形式的转载都请联系作者获得授权并注明出处。