@Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        centerX = w / 2;
        centerY = h / 2;
        radius = w / 3;
        viewW = w;
        viewH = h;

        mbackRectF = new RectF(centerX - radius, centerY - radius, centerX + radius, centerY + radius);
    }
author : engineer
e-mail : yingkongshi11@gmail.com
time   : 2017/12/10
desc   :
version: 1.0
app/src/main/java/home/smart/fly/animations/master/widget/MasterPaintView.java