全屏，获取屏幕大小

//设置全屏
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);
        //获取屏幕大小
        DisplayMetrics dm = new  DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(dm);
        WIDTH_SCREEN = dm.widthPixels;
        HEIGHT_SCREEN = dm.heightPixels;