如何从canvas获取位图（没有setBitmap）

Question

现在，我想在ViewGroup的dispatchDraw（Canvas canvas）中获取位图;只知道Canvas有CanvasFinalizerm和NativeCanvasWrapper。这可能会转换为位图，我希望你可以告诉我如何变换或如何获得 这是我的代码

@Override
protected void dispatchDraw(Canvas canvas) {
    super.dispatchDraw(canvas);
    //canvas get a bitmap  so I copy and  change to draw
    paint.setColor(Color.CYAN);
    canvas.drawCircle(getMeasuredWidth() / 2, getMeasuredHeight() / 2, getMeasuredWidth() / 2, paint);

}