1page.title=Live Wallpapers 2@jd:body 3 4 5<div id="qv-wrapper"> 6<div id="qv"> 7 8 <h2>See also</h2> 9 <ol> 10 <li><a href="{@docRoot}resources/samples/CubeLiveWallpaper/index.html">Live Wallpaper 11sample</a></li> 12 </ol> 13 14</div> 15</div> 16 17<p>Starting with Android 2.1 (API Level 7), users can now enjoy <em>live 18wallpapers</em> — richer, animated, interactive backgrounds — on 19their home screens. A live wallpaper is very similar to a normal Android 20application and has access to all the facilities of the platform: SGL (2D 21drawing), OpenGL (3D drawing), GPS, accelerometers, network access, etc. The 22live wallpapers included on Nexus One demonstrate the use of some of these APIs 23to create fun and interesting user experiences. For instance, the Grass 24wallpaper uses the phone's location to compute sunrise and sunset times in order 25to display the appropriate sky.</p> 26 27<img src="images/live_wallpapers_small.png" style="align:center" /> 28 29<p>Creating your own live wallpaper is easy, especially if you have had 30previous experience with <a 31href="../../../reference/android/view/SurfaceView.html"><code>SurfaceView</code></a> or <a 32href="../../../reference/android/graphics/Canvas.html"><code>Canvas</code></a>. 33To learn how to create a live wallpaper, you should check out the <a 34href="../samples/CubeLiveWallpaper/index.html">CubeLiveWallpaper sample code</a>.</p> 35 36<p>In terms of implementation, a live wallpaper is very similar to a regular 37Android <a href="../../../reference/android/app/Service.html">service</a>. The 38only difference is the addition of a new method, <a 39href="../../../reference/android/service/wallpaper/WallpaperService.html#onCreateEngine()">{@code 40onCreateEngine()}</a>, whose goal is to create a <a 41href="../../../reference/android/service/wallpaper/WallpaperService.Engine.html"> 42<code>WallpaperService.Engine</code></a>. The engine is responsible for 43handling the lifecycle and drawing of a wallpaper. The system provides a surface 44on which you can draw, just like you would with a <code>SurfaceView</code></a>. 45Drawing a wallpaper can be very expensive so you should optimize your code 46as much as possible to avoid using too much CPU, not only for battery life 47but also to avoid slowing down the rest of the system. That is also why the 48most important part of the lifecycle of a wallpaper is <a href="../../../reference/android/service/wallpaper/WallpaperService.Engine.html#onVisibilityChanged%28boolean%29">when it becomes invisible</a>. 49When invisible, such as when the user launches an application that covers 50the home screen, a wallpaper must stop all activity.</p> 51 52<p>The engine can also implement several methods to interact with the user 53or the home application. For instance, if you want your wallpaper to scroll 54along when the user swipes from one home screen to another, you can use <a href="../../../reference/android/service/wallpaper/WallpaperService.Engine.html#onOffsetsChanged%28float,%20float,%20float,%20float,%20int,%20int%29"><code>onOffsetsChanged()</code></a>. 55To react to touch events, simply implement <a href="../../../reference/android/service/wallpaper/WallpaperService.Engine.html#onTouchEvent%28android.view.MotionEvent%29"><code>onTouchEvent(MotionEvent)</code></a>. 56Finally, applications can send arbitrary commands to the live wallpaper. 57Currently, only the standard home application sends commands to the <a 58href="../../../reference/android/service/wallpaper/WallpaperService.Engine.html#onCommand%28java.lang.String,%20int,%20int,%20int,%20android.os.Bundle,%20boolean%29"><code>onCommand()</code></a> 59method of the live wallpaper:</p> 60 61<ul> 62<li><code>android.wallpaper.tap</code>: When the user taps an empty space 63on the workspace. This command is interpreted by the Nexus and Water live 64wallpapers to make the wallpaper react to user interaction. For instance, 65if you tap an empty space on the Water live wallpaper, new ripples appear 66under your finger.</li> 67<li><code>android.home.drop</code>: When the user drops an icon or a widget 68on the workspace. This command is also interpreted by the Nexus and Water 69live wallpapers.</li> 70</ul> 71 72<p>If you are developing a live wallpaper, remember that the feature is 73supported only on Android 2.1 (API level 7) and higher versions of the platform. 74To ensure that your application can only be installed on devices that support 75live wallpapers, remember to add the following to the application's manifest 76before publishing to Android Market:</p> 77 78<ul> 79<li><code><uses-sdk android:minSdkVersion="7" /></code>, which indicates 80to Android Market and the platform that your application requires Android 2.1 or 81higher. For more information, see the <a href="../../../guide/appendix/api-levels.html">API 82Levels</a> and the documentation for the 83<a href="../../../guide/topics/manifest/uses-sdk-element.html"><code><uses-sdk></code></a> 84element.</li> 85<li><code><uses-feature android:name="android.software.live_wallpaper" /></code>, 86which tells Android Market that your application includes a live wallpaper 87Android Market uses this feature as a filter, when presenting users lists of 88available applications. When you declaring this feature, Android Market 89displays your application only to users whose devices support live wallpapers, 90while hiding it from other devices on which it would not be able to run. For 91more information, see the documentation for the 92<a href="../../../guide/topics/manifest/uses-feature-element.html"><code><uses-feature></code></a> 93element.</li> 94</ul> 95 96<p>Many great live wallpapers are already available on Android Market and 97we can't wait to see more!</p> 98
