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Question

I'm trying to update a widget when I got some data from my database. The widget that I'm trying to change is defined as a class variable:

Widget openFriendRequestNotificationWidget = new Container();

I'm using an empty container because I really don't need to render anything at the beginning and leaving it at null is no option.
I've got two functions, one to create my page and the other one the update my openFriendRequestNotificationWidget :

  Widget createFriendsPage() {
    if (currentUser.friends == null) {
      return new Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          openFriendRequestNotificationWidget,
          new Material(
              child: new InkWell(
                child: new Center(
                  child: new Text("Woops, looks like you have no friends yet.\nTap here to find some!", textAlign: TextAlign.center,),
                ),
                onTap: () => createFriendsDialog(),
              )
          )
        ],
      );
    }
    return new Column(
      children: <Widget>[
        openFriendRequestNotificationWidget,
        new Text("ok")
      ],
    );
  }

  void createReceivedFriendRequestsNotification() {
    FirebaseDatabase.instance.reference().child("friend_requests").child(currentUser.uid).once().then((DataSnapshot snap) {
      Map<String, Map<String, String>> response = snap.value;
      if (response != null) {
        this.setState(() {
          print("Changing widget");
          openFriendRequestNotificationWidget = new Container(
            child: new Text("You've got ${response.length.toString()} new friend requests!"),
            color: Colors.black,
          );
        });
      }
    });
  }

The variable is updating in createReceivedFriendRequestsNotification but it is not re-rendering.
Could someone help out?

Answer 1

if you are calling createFriendsPage in initState() , then it means that the code inside initState() is called only once, which is to build the UI. If it's possible, I suggest that you call your createFriendsPage inside the override method build()

   class FriendPage extends StatefullWidget{
          //instantiate your state ..  }

   class FriendsPageState extends State<FriendPage> {
         @override 
         Widget build(Build context) {
               return cteateFriendsPage(); 
         }

         //other methods here ...
     }