Android ViewStub 布局延迟加载

ViewStub本身只占一点内存空间

在调用inflate后  才加载layout属性所指向的layout， 以替换当前ViewStub所占的位置

在某些 需要选择显示何种布局时，就可以使用ViewStub来延迟加载

注意：inflate只能有一次

layout: activity_view_stub.xml

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/btn_show"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="show"
        android:text="显示viewstub指向的layout"/>

    <Button
        android:id="@+id/btn_hide"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/btn_show"
        android:onClick="hide"
        android:text="隐藏viewstub指向的layout"/>

    <ViewStub
        android:id="@+id/vs_stub"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_below="@id/btn_show"
        android:layout="@layout/rorate_bitmap"/>

</RelativeLayout>

public class ViewStubActivity extends Activity {

    ViewStub mViewStub;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_view_stub);

        mViewStub = (ViewStub) findViewById(R.id.vs_stub);

    }

    View inflate;
    public void show(View view) {

        if (inflate == null)
            inflate = mViewStub.inflate();
        else
            inflate.setVisibility(View.VISIBLE);
    }

    public void hide(View view) {

        if (inflate == null)
            inflate = mViewStub.inflate();

        inflate.setVisibility(View.GONE);
    }

}