android - 从 Camera.takePicture() 对 onPictureTaken 的异步调用不会发生以每隔 x 秒保存一次捕获的图像

Question

我正在尝试构建一个 android 应用程序来捕获图像并每隔 x 秒自动将它们保存在 SD 卡上。对于 PictureCallback，从 takePicture() 到 onPictureTaken() 的调用从未发生在我身上。

以下是创建对象的活动，它创建相机对象，并且按钮的 onclick 侦听器调用 takePicture()

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mContext = this;
    prefs = getSharedPreferences(PREFS, 0);
    long timeout = prefs.getLong("TIMEOUT", 5);

    if(checkCameraHardware(this)){
        mCamera = getCameraInstance();
    }

    // Create our Preview view and set it as the content of our activity.
    mPreview = new CameraPreview(this, mCamera);
    preview = (FrameLayout) findViewById(R.id.camera_preview);
    preview.addView(mPreview);

    // Add a listener to the Capture button
    final Button captureButton = (Button) findViewById(R.id.button_capture);

captureButton.setOnClickListener( new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            // get an image from the camera
            takePictures.execute(null);
            captureButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    // get an image from the camera
                    takePictures.cancelPicture();
                    captureButton.setOnClickListener(null);
                }
            });
        }
    });

    takePictures = new Picturetask(timeout);
}

protected void resetPreview(){
    System.out.println("hello reset");
    mCamera.stopPreview();
    mPreview = new CameraPreview(this, mCamera);
    preview.addView(mPreview);
}

@Override
protected void onPause() {
    System.out.println("hello pause");
    super.onPause();
    takePictures.cancelPicture();
    takePictures.cancel(true);
    releaseMediaRecorder();       // if you are using MediaRecorder, release it first
    releaseCamera();              // release the camera immediately on pause event

}

@Override
public void onStart() {
    System.out.println("hello start");
    super.onStart();
    registerReceiver(refreshPreview, new IntentFilter(BROADCAST_PREVIEW));
}

protected void releaseMediaRecorder(){
    System.out.println("hello release");
    if (mMediaRecorder != null) {
        mMediaRecorder.reset();   // clear recorder configuration
        mMediaRecorder.release(); // release the recorder object
        mMediaRecorder = null;
        mCamera.lock();           // lock camera for later use
    }
}

protected void releaseCamera(){
    System.out.println("hello camera release");
    if (mCamera != null){
        mCamera.release();        // release the camera for other applications
        mCamera = null;
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

/** Check if this device has a camera */
private boolean checkCameraHardware(Context context) {
    if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)){
        // this device has a camera
        return true;
    } else {
        // no camera on this device
        return false;
    }
}

/** A safe way to get an instance of the Camera object. */
public static Camera getCameraInstance(){
    System.out.println("hello instance");
    Camera c = null;
    try {
        c = Camera.open(); // attempt to get a Camera instance
    }
    catch (Exception e){
        // Camera is not available (in use or does not exist)
    }
    return c; // returns null if camera is unavailable
}

这是保存捕获图像的逻辑

    protected PictureCallback mPicture = new PictureCallback() {
    @Override
    public void onPictureTaken(byte[] data, Camera camera) {

        File pictureFile = getOutputMediaFile(MEDIA_TYPE_IMAGE);

        try {
 System.out.println("Code never gets called");
            FileOutputStream fos = new FileOutputStream(pictureFile);
            fos.write(data);
            fos.close();                
        } catch (FileNotFoundException e) {
            Log.d(TAG, "File not found: " + e.getMessage());
        } catch (IOException e) {
            Log.d(TAG, "Error accessing file: " + e.getMessage());
        }
    }
};

private class Picturetask extends AsyncTask<String, Void, Boolean> {

    private long timeout;
    private volatile boolean wait = true;

    public Picturetask(long timeout){
        System.out.println("hello");
        this.timeout = 1000 * timeout;
    }

    @Override
    protected Boolean doInBackground(String... arg0) {
        takePicture();
        return null;
    }

    private void takePicture(){
        while(wait){

            System.out.println("Take picture in loop");
            CameraActivity.this.mCamera.takePicture(null, null, mPicture);

            Intent i = new Intent(BROADCAST_PREVIEW);
            sendBroadcast(i);
            try {
                Thread.sleep(timeout);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
                break;
            }
        }
    }
private BroadcastReceiver refreshPreview = new BroadcastReceiver() {

    @Override
    public void onReceive(Context context, Intent intent) {
        mPreview.surfaceChanged(null, 0, 0, 0);
    }
}

Flow 永远不会到达 onPictureTaken() 方法中的打印语句