当用户触摸屏幕并在屏幕上移动手指时，我想在屏幕上画一个圆圈。当在屏幕上移动手指时，圆圈的大小应该改变。当前，当我绘制圆时，多个圆正在绘制。

when (action) {
        MotionEvent.ACTION_DOWN -> {
            mStartX = mx
            mStartY = my
        }
        MotionEvent.ACTION_MOVE -> {
        }
        MotionEvent.ACTION_UP -> {
            mCanvas!!.drawCircle(
                mStartX,
                mStartY,
                calculateRadius(mStartX, mStartY, mx, my),
                mPaint
            )
        }
    }
    invalidate()}

in method onDraw()
 if (mCurrentShape == RECTANGLE) {
        drawRectangle(canvas, mPaint)
    } else if(mCurrentShape == CIRCLE){
        mCanvas!!.drawCircle(
            mStartX,
            mStartY,
            calculateRadius(mStartX, mStartY, mx, my),
            mPaint
        )
    }

问题图片添加在这里