103 lines
5.0 KiB
Plaintext
103 lines
5.0 KiB
Plaintext
page.title=Live Wallpapers
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parent.title=Articles
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parent.link=../browser.html?tag=article
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@jd:body
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<div id="qv-wrapper">
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<div id="qv">
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<h2>See also</h2>
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<ol>
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<li><a href="{@docRoot}resources/samples/CubeLiveWallpaper/index.html">Live Wallpaper
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sample</a></li>
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</ol>
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</div>
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</div>
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<p>Starting with Android 2.1 (API Level 7), users can now enjoy <em>live
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wallpapers</em> — richer, animated, interactive backgrounds — on
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their home screens. A live wallpaper is very similar to a normal Android
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application and has access to all the facilities of the platform: SGL (2D
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drawing), OpenGL (3D drawing), GPS, accelerometers, network access, etc. The
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live wallpapers included on Nexus One demonstrate the use of some of these APIs
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to create fun and interesting user experiences. For instance, the Grass
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wallpaper uses the phone's location to compute sunrise and sunset times in order
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to display the appropriate sky.</p>
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<img src="images/live_wallpapers_small.png" style="align:center" />
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<p>Creating your own live wallpaper is easy, especially if you have had
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previous experience with {@link android.view.SurfaceView} or {@link
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android.graphics.Canvas}.
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To learn how to create a live wallpaper, you should check out the <a
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href="../samples/CubeLiveWallpaper/index.html">CubeLiveWallpaper sample code</a>.</p>
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<p>In terms of implementation, a live wallpaper is very similar to a {@link android.app.Service}.
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The only difference is the addition of a new method, {@link
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android.service.wallpaper.WallpaperService#onCreateEngine()}, whose goal is to create a {@link
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android.service.wallpaper.WallpaperService.Engine}. The engine is responsible for
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handling the lifecycle and drawing of a wallpaper. The system provides a surface
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on which you can draw, just like you would with a {@link android.view.SurfaceView}.
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Drawing a wallpaper can be very expensive so you should optimize your code
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as much as possible to avoid using too much CPU, not only for battery life
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but also to avoid slowing down the rest of the system. That is also why the
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most important part of the lifecycle of a wallpaper is when it becomes visible, as indicated
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by a call to {@link android.service.wallpaper.WallpaperService.Engine#onVisibilityChanged
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onVisibilityChanged()}.
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When invisible, such as when the user launches an application that covers
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the home screen, a wallpaper must stop all activity.</p>
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<p>The engine can also implement several methods to interact with the user
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or the home application. For instance, if you want your wallpaper to scroll
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along when the user swipes from one home screen to another, you can use
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{@link android.service.wallpaper.WallpaperService.Engine#onOffsetsChanged
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onOffsetsChanged()}.
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To react to touch events, simply implement {@link
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android.service.wallpaper.WallpaperService.Engine#onTouchEvent onTouchEvent()}.
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Finally, applications can send arbitrary commands to the live wallpaper.
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Currently, only the standard home application sends commands to the
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{@link android.service.wallpaper.WallpaperService.Engine#onCommand onCommand()}
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method of the live wallpaper:</p>
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<ul>
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<li><code>android.wallpaper.tap</code>: When the user taps an empty space
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on the workspace. This command is interpreted by the Nexus and Water live
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wallpapers to make the wallpaper react to user interaction. For instance,
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if you tap an empty space on the Water live wallpaper, new ripples appear
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under your finger.</li>
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<li><code>android.home.drop</code>: When the user drops an icon or a widget
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on the workspace. This command is also interpreted by the Nexus and Water
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live wallpapers.</li>
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</ul>
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<p>If you are developing a live wallpaper, remember that the feature is
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supported only on Android 2.1 (API level 7) and higher versions of the platform.
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To ensure that your application can only be installed on devices that support
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live wallpapers, remember to add the following to the application's manifest
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before publishing to Google Play:</p>
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<ul>
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<li><code><uses-sdk android:minSdkVersion="7" /></code>, which indicates
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to Google Play and the platform that your application requires Android 2.1 or
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higher. For more information, see the <a href="{@docRoot}guide/appendix/api-levels.html">API
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Levels</a> and the documentation for the
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<a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html"><code><uses-sdk></code></a>
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element.</li>
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<li><code><uses-feature android:name="android.software.live_wallpaper" /></code>,
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which tells Google Play that your application includes a live wallpaper
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Google Play uses this feature as a filter, when presenting users lists of
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available applications. When you declaring this feature, Google Play
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displays your application only to users whose devices support live wallpapers,
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while hiding it from other devices on which it would not be able to run. For
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more information, see the documentation for the
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<a
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href="{@docRoot}guide/topics/manifest/uses-feature-element.html">{@code
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<uses-feature></a>
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element.</li>
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</ul>
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<p>Many great live wallpapers are already available on Google Play and
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we can't wait to see more!</p>
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