如何实现Activity窗口快速变暗

利用只读属性动画+WindowManager

 /*       *@param from\>=0&&from\<=1.0f      * @param to\>=0&&to\<=1.0f      *       * */    private void dimBackground(final float from, final float to) {        final Window window = getWindow();        ValueAnimator valueAnimator = ValueAnimator.ofFloat(from, to);        valueAnimator.setDuration(500);        valueAnimator.addUpdateListener(new AnimatorUpdateListener() {            @Override            public void onAnimationUpdate(ValueAnimator animation) {                WindowManager.LayoutParams params = window.getAttributes();                params.alpha = (Float) animation.getAnimatedValue();                window.setAttributes(params);            }        });        valueAnimator.start();    }