Android Material设计中列表和卡片的创建方法解析

RecyclerView并确定重用项目视图时,布局管理器的利用item的方法，不再是对用户可见。重用(或回收)视图,布局管理器可能会问适配器，替换内容为不同的数据集的元素。回收view时，以这种方式来改进性能：避免创建不必要的view或执行消耗大的findViewById()查询。

RecyclerView提供了如下管理器：

• LinearLayoutManager  横向或纵向的滚动列表
• GridLayoutManager  网格列表
• StaggeredGridLayoutManager  交错的网格列表

  要创建一个自定义布局管理器,需要继承RecyclerView.LayoutManager类

  动画：
  添加和删除item的动画，在RecyclerView默认启用。定制这些动画,需要继承RecyclerView.ItemAnimator类并使用RecyclerView.setItemAnimator()方法。

  例子：
  layout

  <!-- A RecyclerView with some commonly used attributes --> 
  <android.support.v7.widget.RecyclerView 
    android:id="@+id/my_recycler_view" 
    android:scrollbars="vertical" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"/> 
  
  

  activity

  public class MyActivity extends Activity { 
    private RecyclerView mRecyclerView; 
    private RecyclerView.Adapter mAdapter; 
    private RecyclerView.LayoutManager mLayoutManager; 
   
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
      super.onCreate(savedInstanceState); 
      setContentView(R.layout.my_activity); 
      mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view); 
   
      // use this setting to improve performance if you know that changes 
      // in content do not change the layout size of the RecyclerView 
      mRecyclerView.setHasFixedSize(true); //使用固定size 以优化性能 
   
      // use a linear layout manager 
      mLayoutManager = new LinearLayoutManager(this); 
      mRecyclerView.setLayoutManager(mLayoutManager); 
   
      // specify an adapter (see also next example) 
      mAdapter = new MyAdapter(myDataset); 
      mRecyclerView.setAdapter(mAdapter); 
    } 
    ... 
  } 
  
  adapter
  
  public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> { 
    private String[] mDataset; 
   
    // Provide a reference to the views for each data item 
    // Complex data items may need more than one view per item, and 
    // you provide access to all the views for a data item in a view holder 
    public static class ViewHolder extends RecyclerView.ViewHolder { 
      // each data item is just a string in this case 
      public TextView mTextView; 
      public ViewHolder(TextView v) { 
        super(v); 
        mTextView = v; 
      } 
    } 
   
    // Provide a suitable constructor (depends on the kind of dataset) 
    public MyAdapter(String[] myDataset) { 
      mDataset = myDataset; 
    } 
   
    // Create new views (invoked by the layout manager) 
    @Override 
    public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, 
                            int viewType) { 
      // create a new view 
      TextView v = (TextView)LayoutInflater.from(parent.getContext()) 
                  .inflate(R.layout.my_text_view, parent, false); 
      // set the view's size, margins, paddings and layout parameters 
      ... 
      ViewHolder vh = new ViewHolder(v); 
      return vh; 
    } 
   
    // Replace the contents of a view (invoked by the layout manager) 
    @Override 
    public void onBindViewHolder(ViewHolder holder, int position) { 
      // - get element from your dataset at this position 
      // - replace the contents of the view with that element 
      holder.mTextView.setText(mDataset[position]); 
   
    } 
   
    // Return the size of your dataset (invoked by the layout manager) 
    @Override 
    public int getItemCount() { 
      return mDataset.length; 
    } 
  } 
  
  								 
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