Android : Get bitmap from camera preview?

I want to scan QR code from camera. I know about ZXING and i am using it too, but i want to scan the codes in my custom camera preview. All i need is to get a bitmap from camera preview. I am searching about it but unfortunately i didn't got any solution. Here's my implementation

public class CameraPreview extends SurfaceView implements
    SurfaceHolder.Callback {

private SurfaceHolder mHolder;
private Camera mCamera;
Camera.Parameters parameters;
int width, height, imageFormat;

@SuppressWarnings("deprecation")
public CameraPreview(final Context context, Camera camera) {
    super(context);
    _ctx = context;
    mCamera = camera;

    mHolder = getHolder();

    mHolder.addCallback(this);

    mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
        int height) {

    if (mHolder.getSurface() == null) {
        // Preview surface does not exist
        return;
    }

    // Stop preview before making changes
    try {
        mCamera.stopPreview();
    } catch (Exception e) {
        // Ignore : Tried to stop a non-existent preview
    }

    try {
        mCamera.setPreviewDisplay(mHolder);

        // mCamera.startPreview();

    } catch (Exception e) {
        Log.d("SURFACECHANGED",
                "Error starting camera preview: " + e.getMessage());
    }
}

@SuppressLint("NewApi")
@Override
public void surfaceCreated(SurfaceHolder holder) {
    // TODO The Surface has been created, now tell the camera where to draw
    // the preview.
    try {

        mCamera.setPreviewDisplay(holder);
        Toast.makeText(_ctx, "surface created", Toast.LENGTH_SHORT).show();

        mCamera.setOneShotPreviewCallback(new PreviewCallback() {

            @Override
            public void onPreviewFrame(byte[] data, Camera camera) {

                if (camera != null) {

                   int imageFormat = parameters.getPreviewFormat();

                   if (imageFormat == ImageFormat.NV21) {

                      int w = parameters.getPictureSize().width;
                      int h = parameters.getPictureSize().height;
                      YuvImage yuvImage = new YuvImage(mData, imageFormat, w, h, null);
                      Rect rect = new Rect(0, 0, w, h);
                      ByteArrayOutputStream baos = new ByteArrayOutputStream();
                      yuvImage.compressToJpeg(rect, 100, baos);
                      byte[] jData = baos.toByteArray();
                      bitmap = BitmapFactory.decodeByteArray(jData, 0, jData.length);
               }

               else if (imageFormat == ImageFormat.JPEG || imageFormat == ImageFormat.RGB_565) 
               {
                  bitmap = BitmapFactory.decodeByteArray(mData, 0, mData.length);
               }
            }

            if (bitmap != null) {
                 saveImage(bitmap);
            } 
          }
        });
        parameters = mCamera.getParameters();
        mCamera.setParameters(parameters);
        mCamera.startPreview();

    } catch (Exception e) {
        Log.d("SURFACECREATED",
                "Error setting camera preview: " + e.getMessage());
    }

}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
}

}