如何通过代码设置全屏

        // 去掉系统默认标题栏  继承Activity时
       // requestWindowFeature(Window.FEATURE_NO_TITLE);

       //去掉系统默认标题栏 继承AppCompatActivity时
        supportRequestWindowFeature(Window.FEATURE_NO_TITLE);
        //full screen 
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);