Material Design UI Widgets
Android L 开发者预览支持库提供两个新的Widgets，RecyclerView和CardView。使用这两个Widgets可以显示复杂的Listview和卡片布局，这两个Widgets默认使用Material design。
RecyclerView
RecyclerView是一个更高级柔性版本的Listview，RecyclerView是一个能包含很多视图的容器，它能完美的处理循环和滚动。在item动态变化的Listview使用RecyclerView。
RecyclerView使用很简单，因为它提供了：
1、定位item的布局管理器
2、常见的item操作默认动画
你能够灵活的为RecyclerView自定义布局管理器和动画。
使用RecyclerView，必须使用指定一个adapter、定义一个布局管理器。创建adapter必须继承自RecyclerView.Adapter。实施的细节需要看数据类型和需要的视图。
RecyclerView widget
RecyclerView 提供了 LayoutManager，RecylerView 不负责子 View 的布局，我们可以自定义 LayoutManager 来实现不同的布局效果，目前只提供了LinearLayoutManager。 LinearLayoutManager 可以指定方向，默认是垂直， 可以指定水平， 这样就轻松实现了水平的 ListView。
RecyclerView Demo：
1、布局文件
<!-- 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"/>2、Activity文件
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);
// improve performance if you know that changes in content
// do not change the 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);
}
...
}
To create a simple adapter:
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private String[] mDataset;
// Provide a reference to the type of views that you are using
// (custom viewholder)
public static class ViewHolder extends RecyclerView.ViewHolder {
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, null);
// 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;
}
}3、Recycler adapter
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private String[] mDataset;
// Provide a reference to the type of views that you are using
// (custom viewholder)
public static class ViewHolder extends RecyclerView.ViewHolder {
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, null);
// 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;
}
}RecyclerView 的标准化了 ViewHolder， 编写 Adapter 面向的是 ViewHoder 而不在是View 了， 复用的逻辑被封装了， 写起来更加简单。
CardView
CardView继承自FrameLayout类，可以在一个卡片布局中一致性的显示内容，卡片可以包含圆角和阴影。
可以使用android:elevation属性，创建一个阴影的卡片。
怎样指定CardView的属性：
1、使用android:cardCornerRadius属性指定圆角半径
2、使用CardView.setRadius 设置圆角半径。
3、使用 android:cardBackgroundColor属性设置卡片颜色
在创建布局文件中创建CardView：
<!-- A CardView that contains a TextView -->
<android.support.v7.widget.CardView
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:id="@+id/card_view"
android:layout_gravity="center"
android:layout_width="200dp"
android:layout_height="200dp"
card_view:cardCornerRadius="4dp">
<TextView
android:id="@+id/info_text"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</android.support.v7.widget.CardView>/**
* @author 张兴业
参考：
http://developer.android.com/preview/material/ui-widgets.html
