Android设置桌面主要用到了WallPaperService这个类。首先创建自己的类继承WallPaperService并重写onCreateEngine()方法，创建自己的Engine。

 1、创建自己的Engine类GifEngine 继承Engine，重写里面的onSurfaceCreated方法，onVisibilityChanged方法，onSurfaceDestroy方法。在onSurfaceCreate方法中加载gif动画，这里涉及到gif动画的加载与播放，涉及到Movie类，用movie解码gif文件然后画在canvas上，并重复一帧一帧的绘制。这样就能将gif动画渲染到surfaceView上呈现到屏幕。

   onVisibilityChanged方法在桌面可见不可见的时候进行回调，当屏幕可见的时候进行播放，屏幕不可见取消gif绘制。onSurfaceDestroy销毁的时候销毁操作。类如下：

public class GIfWallPaperService extends WallpaperService {private Movie movie;
    private Handler handler;
    private boolean isVisible;
    private int height;
    private int width;
    private int gifWidth;
    private int gifHeigth;

    @Override
    public Engine onCreateEngine() {return new GifEngine();
    }class GifEngine extends Engine {@Override
        public void onSurfaceCreated(SurfaceHolder holder) {super.onSurfaceCreated(holder);
            handler = new Handler();
            try {InputStream inputStream = getContentResolver().openInputStream(Config.filePath);
                movie = Movie.decodeStream(inputStream);
                DisplayMetrics displayMetrics = getResources().getDisplayMetrics();
                height = displayMetrics.heightPixels;
                width = displayMetrics.widthPixels;
                gifWidth = movie.width();
                gifHeigth = movie.height();
            } catch (FileNotFoundException e) {e.printStackTrace();
            }}@Override
        public void onVisibilityChanged(boolean visible) {if (visible) {isVisible = true;
                handler.post(runnable);
            } else {isVisible = false;
                handler.removeCallbacks(runnable);
            }}@Override
        public void onSurfaceDestroyed(SurfaceHolder holder) {super.onSurfaceDestroyed(holder);
            handler.removeCallbacks(runnable);
        }
        private Runnable runnable = new Runnable() {@Override
            public void run() {if (isVisible) {
                    Canvas canvas = getSurfaceHolder().lockCanvas();
                    canvas.save();
                    canvas.scale(2 , 2 );
                    movie.draw(canvas, 0, 0);
                    movie.setTime((int) (System.currentTimeMillis() % movie.duration()));
                    canvas.restore();
                    getSurfaceHolder().unlockCanvasAndPost(canvas);

                    handler.postDelayed(runnable, 50);   //50ms表示每50m绘制一次
                }}};
    }
}

2、配置AndroidMainfest.xml 

<service android:name=".service.GIfWallPaperService"
         android:label="@string/gif_wallpaper"
         android:permission="android.permission.BIND_WALLPAPER">
    <intent-filter>
        <action android:name="android.service.wallpaper.WallpaperService" />
    </intent-filter>

    <meta-data
        android:name="android.service.wallpaper"     

      android:resource="@xml/gif_wallpaper" />

</service>

3、配置gif_wallpaper.xml

    

<?xml version="1.0" encoding="utf-8"?>
<wallpaper xmlns:android="http://schemas.android.com/apk/res/android"
    android:thumbnail="@mipmap/ic_launcher"
    android:description="@string/gif_description"
    />

4、配置strings.xml

<string name="gif_description">gif动态壁纸</string>

5、配置权限

<uses-permission android:name="android.permission.SET_WALLPAPER" />

6、启动GifService

Intent intent = new Intent(WallpaperManager.ACTION_CHANGE_LIVE_WALLPAPER);
intent.putExtra(WallpaperManager.EXTRA_LIVE_WALLPAPER_COMPONENT,new ComponentName(context, GIfWallPaperService.class));
startActivity(intent);

这样就可以实现gif动画加载了