我正在使用系統覆蓋來顯示一些內容。但我希望覆蓋使背景變暗。我該怎么做？這就是我想要的：這就是我得到的方式：這是我設置疊加層的代碼：overlay = LayoutInflater.from(this).inflate(R.layout.activity_popup_dictionary, null);final WindowManager.LayoutParams params = new WindowManager.LayoutParams(        WindowManager.LayoutParams.MATCH_PARENT,        WindowManager.LayoutParams.MATCH_PARENT,        WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY,        WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL,        PixelFormat.TRANSLUCENT);params.gravity = Gravity.BOTTOM;        params.x = 0;params.y = 100;windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);windowManager.addView(overlay, params);