onScale方法不适用于customView

Question

我正在尝试创建一个自定义ImageView，用户可以在其中捏合以调整视图大小，但即使检测器因子始终具有不同的值，该方法也不会执行任何操作。

 public class Art extends AppCompatImageView  {

    private ScaleGestureDetector mScaleDetector;
    private  float mScaleFactor = 1.f;


    public Art(Context context) {
        super(context);
       mScaleDetector = new ScaleGestureDetector(context , new scaleListner());
    }

    public Art(Context context, AttributeSet attrs) {
        super(context, attrs);

       mScaleDetector = new ScaleGestureDetector(context , new scaleListner());
    }



    @Override
    public boolean onTouchEvent(MotionEvent event) {
        event.setLocation(event.getRawX(), event.getRawY());
        mScaleDetector.onTouchEvent(event);

        performClick();

        return true;
    }

    @Override
    public boolean performClick() {
        return super.performClick();
    }


    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

       canvas.save();
       canvas.scale(mScaleFactor, mScaleFactor);
       canvas.restore();

    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
    }



    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        int imageWidth = MeasureSpec.getSize(widthMeasureSpec);
        int imageHeight = MeasureSpec.getSize(heightMeasureSpec);

        int scaledWidth = Math.round(imageWidth * mScaleFactor);
        int scaledHeight = Math.round(imageHeight * mScaleFactor);

        setMeasuredDimension(
                Math.min(imageWidth , scaledWidth) ,
                Math.min(imageHeight , scaledHeight)
        );

    }


    private class scaleListner extends ScaleGestureDetector.SimpleOnScaleGestureListener {

        @Override
        public boolean onScaleBegin(ScaleGestureDetector detector) {
            return super.onScaleBegin(detector);
        }

        @Override
        public boolean onScale(ScaleGestureDetector detector) {

            mScaleFactor *= detector.getScaleFactor();
            mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 5.0f));

            invalidate();
            return super.onScale(detector);
        }
    }
}

并使用添加图像 MainActivity中的setImageResource

任何人都可以帮我解决问题吗？