Activity哀悼模式

    public static void applyGrayMode(Window window) {
        if (window == null) {
            return;
        }
        Paint paint = new Paint();
        ColorMatrix colorMatrix = new ColorMatrix();
        colorMatrix.setSaturation(0);
        paint.setColorFilter(new ColorMatrixColorFilter(colorMatrix));
        window.getDecorView().setLayerType(View.LAYER_TYPE_HARDWARE, paint);
    }