本篇实现一个有意思的玩意儿，视频壁纸，相机壁纸
先上图哈哈：

1.视频壁纸 2.相机壁纸


先从动态壁纸的实现说起吧：

每一个动态壁纸都继承自WallpaperService，其中必须实现的抽象方法onCreateEngine，返回一个Engine对象，实际上所有的绘图与刷新都是由engine完成。如下：

public class VideoLiveWallpaper extends WallpaperService {
    // 实现WallpaperService必须实现的抽象方法  
    public Engine onCreateEngine() {
        return new VideoEngine();
    }



    class VideoEngine extends Engine {


        @Override
        public void onCreate(SurfaceHolder surfaceHolder) {
            super.onCreate(surfaceHolder);

            // 设置处理触摸事件  
            setTouchEventsEnabled(true);

        }
          }

        }

必须在清单文件中进行一些配置，比如：

<!-- 配置动态壁纸Service -->
<service android:label="@string/app_name"
    android:name=".LiveWallpaper"
    android:permission="android.permission.BIND_WALLPAPER">
    <!-- 为动态壁纸配置intent-filter -->
    <intent-filter>
        <action android:name="android.service.wallpaper.WallpaperService" />
    </intent-filter>
    <!-- 为动态壁纸配置meta-data -->
    <meta-data android:name="android.service.wallpaper"
        android:resource="@xml/livewallpaper" />
</service>

比较重要的部分首先是权限android:permission=”android.permission.BIND_WALLPAPER”；
其次service需要响应action：android:name=”android.service.wallpaper.WallpaperService；
接下来接收配置文件。首先在res文件夹下建立一个xml目录，和写appwidget一样。在目录下我们创建一个xml文件：

<wallpaper xmlns:android="http://schemas.android.com/apk/res/android"  
    android:settingsActivity="LiveWallPreference"  
    android:thumbnail="@drawable/ic_launcher"  
    android:description="@string/wallpaper_description"  
    />

然后启动选择壁纸的代码是这样的：

final Intent pickWallpaper = new Intent(Intent.ACTION_SET_WALLPAPER);
        Intent chooser = Intent.createChooser(pickWallpaper, getString(R.string.choose_wallpaper));
        startActivity(chooser);

实现视频壁纸

实现视频壁纸的时候本来打算用mediaplayer实现，后来发现mediaplayer实现在某些机型上报JNI层错误。
于是改用ffmpeg自己实现JNI层，当然这样做的好处是可以更多的定制化，比如示例上的快速播放视频。

主要就一个函数
即把WallpaperService 的Surface传给native的play方法。

public class VideoLiveWallpaper extends WallpaperService {
    // 实现WallpaperService必须实现的抽象方法  
    public Engine onCreateEngine() {
        return new VideoEngine();
    }
    class VideoEngine extends Engine {


        @Override
        public void onCreate(SurfaceHolder surfaceHolder) {
            super.onCreate(surfaceHolder);

                    play(getSurfaceHolder().getSurface());
            // 设置处理触摸事件  
            setTouchEventsEnabled(true);

        }

    static {
        System.loadLibrary("native-lib");
    }
    public native int play(Object surface);
}
```

然后JNI的play方法具体实现。

关键地方都有注释，可以结合我之前分享的ffmpeg源码看 

ffmpeg源码简析（一）结构总览 ：[http://blog.csdn.net/king1425/article/details/70597642

下面是JNI代码：
```C++
JNIEXPORT jint JNICALL
Java_com_ws_ffmpegandroidwallpaper_VideoLiveWallpaper_play
        (JNIEnv *env, jclass clazz, jobject surface) {
    LOGD("play");

    // sd卡中的视频文件地址,可自行修改或者通过jni传入
    //char *file_name = "/storage/emulated/0/ws.mp4";
    char *file_name = "/storage/emulated/0/video.avi";

    av_register_all();

    AVFormatContext *pFormatCtx = avformat_alloc_context();

    // Open video file
    if (avformat_open_input(&pFormatCtx, file_name, NULL, NULL) != 0) {

        LOGD("Couldn't open file:%s\n", file_name);
        return -1; // Couldn't open file
    }

    // Retrieve stream information
    if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
        LOGD("Couldn't find stream information.");
        return -1;
    }

    // Find the first video stream
    int videoStream = -1, i;
    for (i = 0; i < pFormatCtx->nb_streams; i++) {
        if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO
            && videoStream < 0) {
            videoStream = i;
        }
    }
    if (videoStream == -1) {
        LOGD("Didn't find a video stream.");
        return -1; // Didn't find a video stream
    }

    // Get a pointer to the codec context for the video stream
    AVCodecContext *pCodecCtx = pFormatCtx->streams[videoStream]->codec;

    // Find the decoder for the video stream
    AVCodec *pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    if (pCodec == NULL) {
        LOGD("Codec not found.");
        return -1; // Codec not found
    }

    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        LOGD("Could not open codec.");
        return -1; // Could not open codec
    }

    // 获取native window
    ANativeWindow *nativeWindow = ANativeWindow_fromSurface(env, surface);

    // 获取视频宽高
    int videoWidth = pCodecCtx->width;
    int videoHeight = pCodecCtx->height;

    // 设置native window的buffer大小,可自动拉伸
    ANativeWindow_setBuffersGeometry(nativeWindow, videoWidth, videoHeight,
                                     WINDOW_FORMAT_RGBA_8888);
    ANativeWindow_Buffer windowBuffer;

    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        LOGD("Could not open codec.");
        return -1; // Could not open codec
    }

    // Allocate video frame
    AVFrame *pFrame = av_frame_alloc();

    // 用于渲染
    AVFrame *pFrameRGBA = av_frame_alloc();
    if (pFrameRGBA == NULL || pFrame == NULL) {
        LOGD("Could not allocate video frame.");
        return -1;
    }

    // Determine required buffer size and allocate buffer
    // buffer中数据就是用于渲染的,且格式为RGBA
    int numBytes = av_image_get_buffer_size(AV_PIX_FMT_RGBA, pCodecCtx->width, pCodecCtx->height,
                                            1);
    uint8_t *buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));
    av_image_fill_arrays(pFrameRGBA->data, pFrameRGBA->linesize, buffer, AV_PIX_FMT_RGBA,
                         pCodecCtx->width, pCodecCtx->height, 1);

    // 由于解码出来的帧格式不是RGBA的,在渲染之前需要进行格式转换
    struct SwsContext *sws_ctx = sws_getContext(pCodecCtx->width,
                                                pCodecCtx->height,
                                                pCodecCtx->pix_fmt,
                                                pCodecCtx->width,
                                                pCodecCtx->height,
                                                AV_PIX_FMT_RGBA,
                                                SWS_BILINEAR,
                                                NULL,
                                                NULL,
                                                NULL);

    int frameFinished;
    AVPacket packet;
    while (av_read_frame(pFormatCtx, &packet) >= 0) {
        // Is this a packet from the video stream?
        if (packet.stream_index == videoStream) {

            // Decode video frame
            avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);

            // 并不是decode一次就可解码出一帧
            if (frameFinished) {

                // lock native window buffer
                ANativeWindow_lock(nativeWindow, &windowBuffer, 0);

                // 格式转换
                sws_scale(sws_ctx, (uint8_t const *const *) pFrame->data,
                          pFrame->linesize, 0, pCodecCtx->height,
                          pFrameRGBA->data, pFrameRGBA->linesize);

                // 获取stride
                uint8_t *dst = (uint8_t *) windowBuffer.bits;
                int dstStride = windowBuffer.stride * 4;
                uint8_t *src = (pFrameRGBA->data[0]);
                int srcStride = pFrameRGBA->linesize[0];

                // 由于window的stride和帧的stride不同,因此需要逐行复制
                int h;
                for (h = 0; h < videoHeight; h++) {
                    memcpy(dst + h * dstStride, src + h * srcStride, srcStride);
                }

                ANativeWindow_unlockAndPost(nativeWindow);
            }

        }
        av_packet_unref(&packet);
    }

    av_free(buffer);
    av_free(pFrameRGBA);

    // Free the YUV frame
    av_free(pFrame);

    // Close the codecs
    avcodec_close(pCodecCtx);

    // Close the video file
    avformat_close_input(&pFormatCtx);
    return 0;
}
}


```

##相机壁纸
这个简单直接上代码了
最精华的一句： camera.setPreviewDisplay(getSurfaceHolder()); 

```java
package com.ws.ffmpegandroidwallpaper;

import android.hardware.Camera;
import android.service.wallpaper.WallpaperService;
import android.view.MotionEvent;
import android.view.SurfaceHolder;

import java.io.IOException;

public class CameraLiveWallpaper extends WallpaperService {

    public Engine onCreateEngine() {
        return new CameraEngine();
    }


    class CameraEngine extends Engine  {
        private Camera camera;

        @Override
        public void onCreate(SurfaceHolder surfaceHolder) {
            super.onCreate(surfaceHolder);

            startPreview();
            // 设置处理触摸事件  
            setTouchEventsEnabled(true);

        }

        @Override
        public void onTouchEvent(MotionEvent event) {
            super.onTouchEvent(event); 
        }

        @Override
        public void onDestroy() {
            super.onDestroy();
            stopPreview();
        }

        @Override
        public void onVisibilityChanged(boolean visible) {
            if (visible) {
                startPreview();
            } else {
                stopPreview();
            }
        }

        /**
         * 开始预览
         */
        public void startPreview() {
            camera = Camera.open();
            camera.setDisplayOrientation(90);

            try {
                camera.setPreviewDisplay(getSurfaceHolder());
            } catch (IOException e) {
                e.printStackTrace();
            }
            camera.startPreview();

        }

        /**
         * 停止预览
         */
        public void stopPreview() {
            if (camera != null) {
                try {
                    camera.stopPreview();
                    camera.setPreviewCallback(null);
                    // camera.lock();
                    camera.release();
                } catch (Exception e) {
                    e.printStackTrace();
                }
                camera = null;
            }
        }
    }
}  
```

源码下载：http://blog.csdn.net/king1425/article/details/72236225