我已经实现了一个从后台线程拍照的服务,但照片永远不会在我的任何设备上拍摄…这里是代码(下面的日志输出)：

public class PhotoCaptureService extends Service {

private static final String TAG = "PhotoCaptureService";

@Override

public void onStart(Intent intent, int startId) {

super.onStart(intent, startId);

Log.d(TAG, "Starting the PhotoCaptureService");

takePhoto();

}

private void takePhoto() {

Log.d(TAG, "Preparing to take photo");

Camera camera = null;

try {

camera = Camera.open();

} catch (RuntimeException e) {

Log.e(TAG, "Camera not available", e);

return;

}

if (null == camera) {

Log.e(TAG, "Could not get camera instance");

return;

}

Log.d(TAG, "Got the camera, creating the dummy surface texture");

SurfaceTexture dummySurfaceTexture = new SurfaceTexture(0);

try {

camera.setPreviewTexture(dummySurfaceTexture);

} catch (Exception e) {

Log.e(TAG, "Could not set the surface preview texture", e);

}

Log.d(TAG, "Preview texture set, starting preview");

camera.startPreview();

Log.d(TAG, "Preview started");

camera.takePicture(null, null, new Camera.PictureCallback() {

@Override

public void onPictureTaken(byte[] data, Camera camera) {

Log.d(TAG, "Photo taken, stopping preview");

camera.stopPreview();

Log.d(TAG, "Preview stopped, releasing camera");

camera.release();

Log.d(TAG, "Camera released");

}

});

}

记录输出：

D/PhotoCaptureService﹕ Starting the PhotoCaptureService

D/PhotoCaptureService﹕ Preparing to take photo

D/PhotoCaptureService﹕ Got the camera, creating the dummy surface texture

D/PhotoCaptureService﹕ Preview texture set, starting preview

D/PhotoCaptureService﹕ Preview started

此时没有其他任何事情发生,onPictureTaken方法永远不会被调用,并且没有抛出错误或异常.有谁知道为什么会这样？我看过StackOverflow上的每一个相机教程,似乎没什么用.