5.0提供了两个新的Widget,它们使用了Material Design 的style和animation:
它两位于 sdk/extras/android/support/v7/cardview 和 sdk/extras/android/support/v7/RecyclerView
创建列表
RecyclerView组件是一个更先进和灵活的版本的列表视图。这个小部件是一个非常有效率的容器,通过有限的views,可以滚动显示大型数据集。
RecyclerView组件数据集合的元素,可在运行时根据用户操作或网络事件进行改变。
RecyclerView类简化了显示和处理大型数据集,它提供了:
你可以在RecyclerView中灵活定义 布局管理器和动画
要使用RecyclerView组件,您必须指定一个适配器和布局管理器。创建一个适配器,继承RecyclerView.Adapter类。有关更多信息,请参见下面的例子。
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:
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
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{ 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; } }
创建卡片
CardView继承自FrameLayout,以卡片式显示一致的外观。它可以有阴影和圆角
创建一个有阴影的卡片,使用card_view:cardElevation属性。
使用这些属性来定制CardView组件的外观:
例
添加依赖:
gradle依赖
dependencies { ... compile 'com.android.support:cardview-v7:21.0.+' compile 'com.android.support:recyclerview-v7:21.0.+' }