ViewStub

 ViewStub和Include标签都是实现UI重用，区别在ViewStub在你需要时渲染主界面。可以通过inflate,setvisibility方法让ViewStub渲染的UI上。

stub.xml文件

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout
    xmlns:android = "http://schemas.android.com/apk/res/android"
    android:layout_width = "match_parent"
    android:layout_height = "match_parent"
    android:tag="stub" >
    <TextView android:text="TextView"
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"></TextView>
</LinearLayout>

main2.xml文件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="6dip">

    <ImageView
        android:id="@+id/icon"

        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        android:layout_alignParentBottom="true"
        android:layout_marginRight="6dip"
        android:src="@drawable/icon" />

    <Button android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@id/icon"
         android:layout_marginRight="6dip"
        android:text="button1"/>
    <ViewStub
        android:id="@+id/stub"
        android:tag="viewStub"
        android:layout="@layout/stub"
android:inflateId="@+id/root" //该属性指重写stub.xml中root view 的id
        android:layout_above="@id/button1"
         android:layout_marginRight="6dip"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
    />
    <Button
        android:id="@+id/button2"
        android:layout_above="@id/stub"
        android:layout_width="wrap_content"
         android:layout_marginRight="6dip"
        android:layout_height="wrap_content"
        android:text="button2"/>

</RelativeLayout>

code

 

public class LayoutActivity extends Activity implements OnClickListener{
    /** Called when the activity is first created. */

    Button button1;
    //View vs;
    ViewStub vs;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main2);
        button1 = (Button)findViewById(R.id.button1);
       // vs = ((ViewStub)findViewById(R.id.stub)).inflate();
        vs = ((ViewStub)findViewById(R.id.stub));
        button1.setOnClickListener(this);
    }
    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        vs.inflate();
        //vs.inf
        Log.e("will", ""+vs.getTag());
        //vs.setVisibility(View.VISIBLE);
    }
}

启动后界面截图

单击Button1后

注意：vs.setVisibility和vs.inflate()方法都可以让ViewStub inflat 被包含的UI，通过sdk tools下hierarchy工具可以看出，当ViewStub 被inflate后，ViewStub会在hierarchy图中移除，因此没有必要长期保存和ViewStub有关的引用，看sdk中是这样描述的

It is very important to remember that after the stub is inflated, the stub is removed from the view hierarchy. As such, it is unnecessary to keep a long-lived reference, for instance in an class instance field, to a ViewStub.

A ViewStub is a great compromise between ease of programming and efficiency. Instead of inflating views manually and adding them at runtime to your view hierarchy, simply use a ViewStub. It's cheap and easy. The only drawback of ViewStub is that it currently does not support the <merge /> tag.