Android how to get left top right bottom in SimpleOnScaleGestureListener.onScale?

Question

I'm going to scale surfaceview with ScaleGestureDetector, not onDraw().

How to get CustomSurfaceView's left top right bottom in SimpleOnScaleGestureListener.onScale?

private SimpleOnScaleGestureListener mSimpleListener = new ScaleGestureDetector.SimpleOnScaleGestureListener() {

    @Override
    public boolean onScale(ScaleGestureDetector detector) {

        int left = (int) (detector.getPreviousSpanX());
        int top = (int) (detector.getPreviousSpanY());
        int right = (int) (detector.getCurrentSpanX()-detector.getPreviousSpanX());
        int bottom = (int) (detector.getCurrentSpanY()-detector.getPreviousSpanY());


        mCustomSurfaceView.layout(left, top, right, bottom);


        invalidate();


        return true;
    };

};