@Override
        public void onScale(float scaleFactor, float focusX, float focusY) {
            if ((getScale() < mMaxScale || scaleFactor < 1f) && (getScale() > mMinScale || scaleFactor > 1f)) {
                if (mScaleChangeListener != null) {
                    mScaleChangeListener.onScaleChange(scaleFactor, focusX, focusY);
                }
                mSuppMatrix.postScale(scaleFactor, scaleFactor, focusX, focusY);
                checkAndDisplayMatrix();
            }
        }
The component of {@link PhotoView} which does the work allowing for zooming, scaling, panning, etc.
It is made public in case you need to subclass something other than {@link ImageView} and still
gain the functionality that {@link PhotoView} offers
main/src/main/java/com/quxianggif/common/view/photoview/PhotoViewAttacher.java