Asynchronous call to onPictureTaken from Camera.takePicture() not occurring for saving captured images every x seconds

Question

I am trying to build an android app to capture images and save them on SD card every x seconds automatically. The call from takePicture() to onPictureTaken() for PictureCallback never occurs for me.

Following is the activity on create object which creates the camera object and for button's onclick listener calls the 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
}

This is the logic to save captured images

    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 never reaches the print statements in the onPictureTaken() methods `