RecyclerView(5)官方教程带简单示例

Create Lists

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　　The RecyclerView widget is a more advanced and flexible version of ListView. This widget is a container for displaying large data sets that can be scrolled very efficiently by maintaining a limited number of views. Use the RecyclerView widget when you have data collections whose elements change at runtime based on user action or network events.

RecyclerView比listview更高级灵活，适合显示由用户动作或网络事件而变化的大数据集合。主要是通过下面几点：

The RecyclerView class simplifies the display and handling of large data sets by providing:

• Layout managers for positioning items
• Default animations for common item operations, such as removal or addition of items

You also have the flexibility to define custom layout managers and animations for RecyclerView widgets.

RecyclerView，LayoutManager ，adapter，数据库之间的关系图

　　　　　　　　　　　　　　　　Figure 1. The RecyclerView widget.

　　To use the RecyclerView widget, you have to specify an adapter and a layout manager. To create an adapter, extend the RecyclerView.Adapter class. The details of the implementation depend on the specifics of your dataset and the type of views. For more information, see the examples below.

　　Figure 2 - Lists with RecyclerView.

　　A layout manager positions item views inside a RecyclerView and determines when to reuse item views that are no longer visible to the user. To reuse (or recycle) a view, a layout manager may ask the adapter to replace the contents of the view with a different element from the dataset. Recycling views in this manner improves performance by avoiding the creation of unnecessary views or performing expensivefindViewById() lookups.

RecyclerView可以使用的3个 layout manager

RecyclerView provides these built-in layout managers:

• LinearLayoutManager shows items in a vertical or horizontal scrolling list.
• GridLayoutManager shows items in a grid.
• StaggeredGridLayoutManager shows items in a staggered grid.

To create a custom layout manager, extend theRecyclerView.LayoutManager class.

Animations

自定义RecyclerView 动画的方法，继承 RecyclerView.ItemAnimator 然后调用 RecyclerView.setItemAnimator() 设置下。

　　Animations for adding and removing items are enabled by default in RecyclerView. To customize these animations, extend the RecyclerView.ItemAnimator class and use the RecyclerView.setItemAnimator() method.

Examples

　　The following code example demonstrates how to add the RecyclerView to a 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"/>

　　Once you have added a RecyclerView widget to your layout, obtain a handle to the object, connect it to a layout manager, and attach an adapter for the data to be displayed:

 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);
 
         // 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);
     }
     ...
 }

　　The adapter provides access to the items in your data set, creates views for items, and replaces the content of some of the views with new data items when the original item is no longer visible. The following code example shows a simple implementation for a data set that consists of an array of strings displayed using TextViewwidgets:

 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
         View v = 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;
     }
 }