Flutter error: setState() called after dispose()

0
votes

I wrote code to fetch data every 60 seconds and display on the screen. When app launched it shows errors in debug console. Code working fine, gets data every 60 sec and shows on the screen.

Error:

E/flutter ( 2021): #6 _CustomZone.bindUnaryCallbackGuarded. (dart:async/zone.dart:1207:26) E/flutter ( 2021): #7 _rootRunUnary (dart:async/zone.dart:1370:13) E/flutter ( 2021): #8 _CustomZone.runUnary (dart:async/zone.dart:1265:19) E/flutter ( 2021): #9 _CustomZone.bindUnaryCallback. (dart:async/zone.dart:1191:26) E/flutter ( 2021): #10 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:395:19) E/flutter ( 2021): #11 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:426:5) E/flutter ( 2021): #12 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12) E/flutter ( 2021): E/flutter ( 2021): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: setState() called after dispose(): _EvrokoVipScreenState#98462(lifecycle state: defunct, not mounted) E/flutter ( 2021): This error happens if you call setState() on a State object for a widget that no longer appears in the widget tree (e.g., whose parent widget no longer includes the widget in its build). This error can occur when code calls setState() from a timer or an animation callback. E/flutter ( 2021): The preferred solution is to cancel the timer or stop listening to the animation in the dispose() callback. Another solution is to check the "mounted" property of this object before calling setState() to ensure the object is still in the tree. E/flutter ( 2021): This error might indicate a memory leak if setState() is being called because another object is retaining a reference to this State object after it has been removed from the tree. To avoid memory leaks, consider breaking the reference to this object during dispose().

  void initState() {
    // TODO: implement initState
    super.initState();
    if (mounted) {
      fetchDataVip();
      new Timer.periodic(Duration(seconds: 60), (Timer t) => setState(() {}));
    }
  }
2
flutterdart

2 Answers

1
votes

You need to cancel your timer when your widget is disposed:

void initState() {
  super.initState();
  fetchDataVip();
  new Timer.periodic(Duration(seconds: 60), (Timer t) {
    if (!mounted) {
      timer.cancel();
    } else {
      setState(() {});
    }
  });
}

And you don't need to check whether or not your widget is mounted in the initState.

1
votes

I think you should dispose of the timer after using it. It should be something like this.

late var timer;
void initState() {
// TODO: implement initState
super.initState();
if (mounted) {
  fetchDataVip();
  timer = new Timer.periodic(Duration(seconds: 60), (Timer t) => setState(() {}));
}
}
  
@override
void dispose() {
  timer.cancel();
  super.dispose();
}