ActionBar官方教程(2)选主题让应用支或不支持ActionBar及支持ActionBar的应用如何隐藏和显示

Adding the Action Bar

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　　As mentioned above, this guide focuses on how to use the ActionBar APIs in the support library. So before you can add the action bar, you must set up your project with the appcompat v7 support library by following the instructions in the Support Library Setup.

Once your project is set up with the support library, here's how to add the action bar:

1. Create your activity by extending ActionBarActivity.
2. Use (or extend) one of the Theme.AppCompat themes for your activity. For example:

   <activity android:theme="@style/Theme.AppCompat.Light" ... >

　　Now your activity includes the action bar when running on Android 2.1 (API level 7) or higher.

On API level 11 or higher

　　The action bar is included in all activities that use the Theme.Holo theme (or one of its descendants), which is the default theme when either the targetSdkVersion or minSdkVersion attribute is set to "11" or higher. If you don't want the action bar for an activity, set the activity theme to Theme.Holo.NoActionBar.

　　主题Theme.Holo.NoActionBar不支持ActionBar,Theme.Holo 支持ActionBar

Removing the action bar

You can hide the action bar at runtime by calling hide(). For example:

 ActionBar actionBar = getSupportActionBar();
 actionBar.hide();

On API level 11 or higher

　　Get the ActionBar with the getActionBar() method.

When the action bar hides, the system adjusts your layout to fill the screen space now available. You can bring the action bar back by calling show().

隐藏:ActionBar.hidden(),显示:ActionBar.show()

　　Beware that hiding and removing the action bar causes your activity to re-layout in order to account for the space consumed by the action bar. If your activity often hides and shows the action bar, you might want to enable overlay mode. Overlay mode draws the action bar in front of your activity layout, obscuring the top portion. This way, your layout remains fixed when the action bar hides and re-appears. To enable overlay mode, create a custom theme for your activity and set windowActionBarOverlay to true. For more information, see the section below about Styling the Action Bar.

注意: 如果经常隐藏,显示,那么要用overlay mode