private void drawFlippingShadeShine(Canvas canvas) {
        final float degreesFlipped = getDegreesFlipped();
        if (degreesFlipped < 90) {
            final int alpha = (int) ((degreesFlipped / 90f) * MAX_SHINE_ALPHA);
            mShinePaint.setAlpha(alpha);
            canvas.drawRect(isFlippingVertically() ? mBottomRect : mRightRect,
                    mShinePaint);
        } else {
            final int alpha = (int) ((Math.abs(degreesFlipped - 180) / 90f) * MAX_SHADE_ALPHA);
            mShadePaint.setAlpha(alpha);
            canvas.drawRect(isFlippingVertically() ? mTopRect : mLeftRect,
                    mShadePaint);
        }
    }
will draw a shade if flipping on the previous(top/left) half and a shine
if flipping on the next(bottom/right) half

@param canvas
app/src/main/java/home/smart/fly/animations/customview/flipview/FlipView.java