flutter - Flutter错误:未处理的异常:NoSuchMethodError:在空调用了 'findAncestorStateOfType'方法

Question

每次登录时，都会出现以下错误。
我发现Navigator.pushReplacement出现了一些问题，该问题在控制台中产生了错误，但仍然允许我进行导航。
不知道如何解决此错误。
以下代码是我正在使用的代码。请让我知道是否有任何错误可以解决。

class WelcomeScreen extends StatefulWidget {
  @override
  _WelcomeScreenState createState() => _WelcomeScreenState();
}

class _WelcomeScreenState extends State<WelcomeScreen>
    with SingleTickerProviderStateMixin {
  startTime() async {
    var _duration = Duration(seconds: 5);
    return Timer(_duration, navigationPage);
  }

  void navigationPage() {
    Navigator.pushReplacement(
      context,
      MaterialPageRoute(
        builder: (context) => FirstTimeUserOnly(),
      ),
    );
  }

  @override
  void initState() {
    super.initState();
    startTime();
  }


  final int delayedAmount = 100;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
           Text('Welcome'),
           Logo(),         
          ],
        ),
      ),
    );
  }
}

这是我得到的错误

E/flutter (16323): Tried calling: findAncestorStateOfType<NavigatorState>()
E/flutter (16323): #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
E/flutter (16323): #1      Navigator.of (package:flutter/src/widgets/navigator.dart:2115:19)
E/flutter (16323): #2      Navigator.pushReplacement (package:flutter/src/widgets/navigator.dart:1781:22)
E/flutter (16323): #3      _WelcomeScreenState.navigationPage (package:/welcome_screen.dart:23:15)
E/flutter (16323): #4      _rootRun (dart:async/zone.dart:1180:38)
E/flutter (16323): #5      _CustomZone.run (dart:async/zone.dart:1077:19)
E/flutter (16323): #6      _CustomZone.runGuarded (dart:async/zone.dart:979:7)
E/flutter (16323): #7      _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:1019:23)
E/flutter (16323): #8      _rootRun (dart:async/zone.dart:1184:13)
E/flutter (16323): #9      _CustomZone.run (dart:async/zone.dart:1077:19)
E/flutter (16323): #10     _CustomZone.bindCallback.<anonymous closure> (dart:async/zone.dart:1003:23)
E/flutter (16323): #11     Timer._createTimer.<anonymous closure> (dart:async-patch/timer_patch.dart:23:15)
E/flutter (16323): #12     _Timer._runTimers (dart:isolate-patch/timer_impl.dart:398:19)
E/flutter (16323): #13     _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:429:5)
E/flutter (16323): #14     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12)
E/flutter (16323): 

Answer 1

试试这个，定时器给你错误

class WelcomeScreen extends StatefulWidget {
  @override
  _WelcomeScreenState createState() => _WelcomeScreenState();
}

class _WelcomeScreenState extends State<WelcomeScreen>
    with SingleTickerProviderStateMixin {

  Timer _timer;
  void startTime() async{
   _timer = Timer(new Duration(seconds: 5), navigationPage);
  }

  void navigationPage() {
    Navigator.pushReplacement(
      context,
      MaterialPageRoute(
        builder: (context) => FirstTimeUserOnly(),
      ),
    );
  }

  @override
  void initState() {
    super.initState();
    startTime();
  }

@override
  void dispose() {
    super.dispose();
    _timer.cancel();
  }

  final int delayedAmount = 100;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
           Text('Welcome'),
           Logo(),         
          ],
        ),
      ),
    );
  }
}