Calling setState() during build without user interaction

Question

What I did :

• I have integrated FCM (Firebase Cloud Messaging) in my flutter app.
• I shared the context and the setState() of each page in static variables with these two lines getting called in all the build functions of my pages :

@override
Widget build(BuildContext context) {
    StaticClass.currentContext = context;
    StaticClass.currentSetState = this.setState;
    return ... ;
}

• I created a callback to handle the coming notifications when the app is running

fcm.configure( onMessage: (){
    StaticClass.currentSetState((){
        Navigator.pushNamed(StaticClass.currentContext, "/notifications");
  });
});

What happened :

• I got this error:

 ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══
...
setState() or markNeedsBuild() called during build.
This Overlay widget cannot be marked as needing to build because the framework is already in the process of building widgets.
...

Explanations :

• I can't update the page (by using context or calling setState()) when the framework is building
• This problem doesn't happen when this function is called with a user interaction

What I want :

• Is there a way to repair my code or am I doing something wrong ?

OR

• Is there any other solution to go to another Page when onMessage() is triggered ?

OR

• Is there a way to know when the build function completes, to setState() without any problem ?

---

Please Help I'm stuck here

Answer 1

You can call setState after rendering is done by adding a post frame callback with addPostFrameCallback method. This will be called only once and after build process is done.

WidgetsBinding.instance.addPostFrameCallback((_) => setState(() {}));