ViewAnimator
public class ViewAnimator
extends FrameLayout
FrameLayout容器的基类，用于在其视图之间切换时执行动画。
我们都了解FrameLayout布局的特性，在FrameLayout中添加的View都默认位于左上角，按照添加的顺序，最后添加的View位置最上层。
ViewAnimator的使用就是调整ViewAnimator包裹的子View的显示层次，可以通过setDisplayedChild(int whichChild)方法，设置哪一个子View将被显示。
布局
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/sample_main_layout">
<ViewAnimator
android:id="@+id/sample_output"
android:layout_width="match_parent"
android:layout_height="0px"
android:layout_weight="1">
<ScrollView
style="@style/Widget.SampleMessageTile"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
style="@style/Widget.SampleMessage"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingLeft="@dimen/horizontal_page_margin"
android:paddingRight="@dimen/horizontal_page_margin"
android:paddingTop="@dimen/vertical_page_margin"
android:paddingBottom="@dimen/vertical_page_margin"
android:text="@string/intro_message" />
</ScrollView>
<fragment
android:name="com.example.android.common.logger.LogFragment"
android:id="@+id/log_fragment"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</ViewAnimator>
<View
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="@android:color/darker_gray" />
<FrameLayout
android:id="@+id/sample_content_fragment"
android:layout_weight="2"
android:layout_width="match_parent"
android:layout_height="0px" />
</LinearLayout>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
tools:ignore="AppCompatResource">
<item android:id="@+id/menu_toggle_log"
android:showAsAction="always"
android:title="Show Log" />
</menu>
Activity
public class MainActivity extends SampleActivityBase {
// Whether the Log Fragment is currently shown
private boolean mLogShown;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
SwipeRefreshListFragmentFragment fragment = new SwipeRefreshListFragmentFragment();
transaction.replace(R.id.sample_content_fragment, fragment);
transaction.commit();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
MenuItem logToggle = menu.findItem(R.id.menu_toggle_log);
//R.id.sample_output对应的组件是否是ViewAnimator或其子类的一个实例，若是，menu_toggle_log，显示
logToggle.setVisible(findViewById(R.id.sample_output) instanceof ViewAnimator);
//logFragment显示的状态不同显示不同字符
logToggle.setTitle(mLogShown ? Hide Log: Show Log);
return super.onPrepareOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
//用于修改menu_toggle_log显示的字符串及ViewAnimator显示的view
switch(item.getItemId()) {
case R.id.menu_toggle_log:
mLogShown = !mLogShown;
ViewAnimator output = (ViewAnimator) findViewById(R.id.sample_output);
if (mLogShown) {
//显示LogFragment
output.setDisplayedChild(1);
} else {
//显示user guide
output.setDisplayedChild(0);
}
//使Activity的选项菜单无效。
//这将导致菜单的相关演示文稿通过在下一次请求菜单时
//通过调用onCreateOptionsMenu和onPrepareOptionsMenu进行完全更新。
supportInvalidateOptionsMenu();
return true;
}
return super.onOptionsItemSelected(item);
}
}
