使用scaleFocus缩放画布会导致跳转

Question

我正在使用自定义视图，可以使用缩放手势对其进行缩放。当我不使用缩放焦点时，一切正常。但是，一旦我像这样canvas.scale(mScaleFactor, mScaleFactor, scaleFocus[0], scaleFocus[1]);进行操作，它就会在缩小到某些低比例因子的同时引起跳跃。这是视图的简化版本，它说明了问题：

public class TestView extends FrameLayout {

private ScaleGestureDetector mScaleGestureDetector;
private float mScaleFactor = 1.f;
private float mMinScaleFactor = 0.4f;
private static final float MAX_SCALE_FACTOR = 2.0f;
private Matrix canvasMatrix = new Matrix();
float[] scaleFocus = new float[2];
private Rect clipBounds = new Rect();

private static final String TAG = "TestView";

public TestView(@NonNull Context context) {
    super(context);
    sharedConstructor();
}

public TestView(@NonNull Context context, @Nullable AttributeSet attrs) {
    super(context, attrs);
    sharedConstructor();
}

public TestView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    sharedConstructor();
}

public void setChildViews() {
    ImageView imageView = new ImageView(getContext());
    LayoutParams layoutParams = new LayoutParams(StateUtil.screenWidth*2, StateUtil.screenHeight*2);
    layoutParams.gravity = Gravity.CENTER;
    imageView.setLayoutParams(layoutParams);
    imageView.setImageResource(R.drawable.test);
    canvasMatrix.set(getMatrix());

    addView(imageView);

    //some additional views are added here
}

private void sharedConstructor(){
    mScaleGestureDetector = new ScaleGestureDetector(getContext(), mScaleGestureListener);

    setChildViews();
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    return mScaleGestureDetector.onTouchEvent(event) || super.onTouchEvent(event);
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.getClipBounds(clipBounds);
    canvas.scale(mScaleFactor, mScaleFactor, scaleFocus[0], scaleFocus[1]);

    canvas.getMatrix().invert(canvasMatrix);
    canvas.save();
}

private final ScaleGestureDetector.OnScaleGestureListener mScaleGestureListener
        = new ScaleGestureDetector.SimpleOnScaleGestureListener() {

    @Override
    public boolean onScale(ScaleGestureDetector detector) {

        scaleFocus[0] = detector.getFocusX();
        scaleFocus[1] = detector.getFocusY();

        canvasMatrix.mapPoints(scaleFocus);
        if (clipBounds.contains((int) scaleFocus[0], (int) scaleFocus[1])){
            mScaleFactor *= detector.getScaleFactor();
            mScaleFactor = Math.max(mMinScaleFactor, Math.min(mScaleFactor, MAX_SCALE_FACTOR));
            TestView.this.invalidate();
        }

        return true;
    }
};

}

这是我的设备上的样子：

我尝试了this answer的解决方案，但对我来说不起作用。即使我不打super.onTouchEvent(event);，问题仍然会发生。

有什么想法会导致它以及如何解决？