android.util.AndroidRuntimeException: requestFeature() must be called before adding content 錯誤解決方法

Activity全屏，網上的代碼如下：
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    this.requestWindowFeature(Window.FEATURE_NO_TITLE);//去掉標題欄
    this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);//去掉信息欄

    setContentView(R.layout.activity_main);
}

但在AS中，會提示錯誤：
android.util.AndroidRuntimeException: requestFeature() must be called before adding content

解決如下：
protected void onCreate(Bundle savedInstanceState) {
    this.requestWindowFeature(Window.FEATURE_NO_TITLE);//去掉標題欄
    this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);//去掉信息欄
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}