在位图上为圆形着色

Question

我正在处理获取图像并将其显示在图像视图中的应用程序。当用户调整屏幕时，我希望在再次触摸屏幕后，该圆圈覆盖的图像（定位的圆圈是触摸屏幕）在该区域保持颜色。 我能够在图像上绘制圆圈但是当再次触摸屏幕时，图像不会保持颜色。

class DrawingView extends SurfaceView {

    private final SurfaceHolder surfaceHolder;
    private final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private Bitmap bitmap1 = null;
    private Bitmap bitmap2 = null;

    private final Point node = new Point();

    public DrawingView(Context context) {
        super(context);
        surfaceHolder = getHolder();
        paint.setColor(Color.RED);
        paint.setStyle(Style.FILL);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if(event.getAction() == MotionEvent.ACTION_DOWN) {
            if (surfaceHolder.getSurface().isValid()) {
                node.x= (int)event.getX();
                node.y = (int)event.getY();
                Canvas canvas = surfaceHolder.lockCanvas();
                bitmap1 = BitmapFactory.decodeResource(getResources(), R.drawable.nic_eyes);
                canvas.drawBitmap(bitmap1, 0, 0, null);
                canvas.drawCircle(event.getX(), event.getY(), 50, paint);

                bitmap2 = bitmap1.copy(bitmap1.getConfig(),true);
                surfaceHolder.unlockCanvasAndPost(canvas);
                photo = bitmap2;//photo is used for saving the modified image into galery

            }
        }
        return false;
    }

}

有什么建议吗？