title: Q:Flutter How to get value from parameter inside class
body: <p>I'm newbie for android and flutter development, I want to ask something about push notification, I build firebase_messaging by own self because its not support big notification image</p>
  
  <p>The problem is I cant get the _url</p>
  
  <pre><code>  int _selectedTab = 1;
    static String _url = "";
    static const platform =
        const MethodChannel('com.example.loop_app_flutter_v2');
  
    @override
    Future&lt;void&gt; _firebaseMessageListener() async {
      String getRedirect;
      String url;
      try {
        final String result =
            await platform.invokeMethod('getFirebaseMessagePayload');
        getRedirect = '$result';
        Map&lt;String, dynamic&gt; notif = jsonDecode(getRedirect);
        url = notif["url"]; //payload success and url show up
  
      } on PlatformException catch (e) {
        getRedirect = "Failed : '${e.message}'.";
      }
      this.loadNotificationData(getRedirect);
      setState(() {
        _url = url; // i want to assign url to _url and put in List Widget
        print(url); //print show up url
      });
    }
  
  
    @override
    void initState() {
      _firebaseMessageListener();
  }
  
    final List&lt;Widget&gt; _children = [
      new MainArtikel(),
      new Webpage(url: _url),
      new FeedBack(),
      new Setting()
    ];
  
  
  </code></pre>