Android L 開發者預覽支持庫提供兩個新的Widgets,RecyclerView和CardView。使用這兩個Widgets可以顯示覆雜的Listview和卡片佈局,這兩個Widgets默認使用Material design。
RecyclerView
RecyclerView是一個更高級柔性版本的Listview,RecyclerView是一個能包含很多視圖的容器,它能完美的處理循環和滾動。在item動態變化的Listview使用RecyclerView。
RecyclerView使用很簡單,因爲它提供了:
1、定位item的佈局管理器
2、常見的item操作默認動畫
你能夠靈活的爲RecyclerView自定義佈局管理器和動畫。
使用RecyclerView,必須使用指定一個adapter、定義一個佈局管理器。創建adapter必須繼承自RecyclerView.Adapter。實施的細節需要看數據類型和需要的視圖。
RecyclerView widget
RecyclerView 提供了 LayoutManager,RecylerView 不負責子 View 的佈局,我們可以自定義 LayoutManager 來實現不同的佈局效果,目前只提供了LinearLayoutManager。 LinearLayoutManager 可以指定方向,默認是垂直, 可以指定水平, 這樣就輕鬆實現了水平的 ListView。
RecyclerView Demo:
1、佈局文件
<!-- 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 的標準化了 ViewHolder, 編寫 Adapter 面向的是 ViewHoder 而不在是View 了, 複用的邏輯被封裝了, 寫起來更加簡單。
CardView
CardView繼承自FrameLayout類,可以在一個卡片佈局中一致性的顯示內容,卡片可以包含圓角和陰影。
可以使用android:elevation屬性,創建一個陰影的卡片。
怎樣指定CardView的屬性:
1、使用android:cardCornerRadius屬性指定圓角半徑
2、使用CardView.setRadius 設置圓角半徑。
3、使用 android:cardBackgroundColor屬性設置卡片顏色
在創建佈局文件中創建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>
參考:
http://developer.android.com/preview/material/ui-widgets.html