ActionBar官方教程(1)简介及各区域介绍

Action Bar

　　The action bar is a window feature that identifies the user location, and provides user actions and navigation modes. Using the action bar offers your users a familiar interface across applications that the system gracefully adapts for different screen configurations.

　　The action bar is split into four different functional areas that apply to most apps.

图中和部分如下:

1,App icon

　　The app icon establishes your app's identity. It can be replaced with a different logo or branding if you wish. Important: If the app is currently not displaying the top-level screen, be sure to display the Up caret to the left of the app icon, so the user can navigate up the hierarchy. For more discussion of Up navigation, see the Navigation pattern.

　　App icon with and without "up" affordance. 

2,View control

　　If your app displays data in different views, this segment of the action bar allows users to switch views. Examples of view-switching controls are drop-down menus or tab controls. For more information on view-switching, see the App Structure pattern.

　　If your app doesn't support different views, you can also use this space to display non-interactive content, such as an app title or longer branding information.

3,Action buttons

　　Show the most important actions of your app in the actions section. Actions that don't fit in the action bar are moved automatically to the action overflow. Long-press on an icon to view the action's name.

4,Action overflow

　　Move less often used actions to the action overflow.

The action bar provides several key functions:

• Provides a dedicated space for giving your app an identity and indicating the user's location in the app.
• Makes important actions prominent and accessible in a predictable way (such as Search).
• Supports consistent navigation and view switching within apps (with tabs or drop-down lists).

For more information about the action bar's interaction patterns and design guidelines, see the Action Bar design guide.

The ActionBar APIs were first added in Android 3.0 (API level 11) but they are also available in the Support Library for compatibility with Android 2.1 (API level 7) and above.

This guide focuses on how to use the support library's action bar, but if your app supports only Android 3.0 or higher, you should use the ActionBar APIs in the framework. Most of the APIs are the same—but reside in a different package namespace—with a few exceptions to method names or signatures that are noted in the sections below.

Caution: Be certain you import the ActionBar class (and related APIs) from the appropriate package:

• If supporting API levels lower than 11: 
  import android.support.v7.app.ActionBar
• If supporting only API level 11 and higher: 
  import android.app.ActionBar

Note: If you're looking for information about the contextual action bar for displaying contextual action items, see the Menu guide.