抛出另一个异常：'package:flutter/src/widgets/navigator.dart': Failed assertion: line 2216 pos 12: ':_debugLocked': is not true

Question

My app was running good I just update the code in one file and I am receiving this error before that error every page was navigating perfectly and now all the pages are good to work instead of this page I am navigating to this page from home page Another exception was thrown: 'package:flutter/src/widgets/navigator.dart': Failed assertion: line 2216 pos 12: ':_debugLocked'. is not true. I do not know where is the issue now.

import 'package:custom_chewie/custom_chewie.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:video_player/video_player.dart';
import 'package:firebase_admob/firebase_admob.dart';

class ChewieDemo extends StatefulWidget {
  final String title;

  ChewieDemo({this.title = 'Chewie Demo'});

  @override
  State<StatefulWidget> createState() {
    return new _ChewieDemoState();
  }
}

class _ChewieDemoState extends State<ChewieDemo> {
  int counter=0;
  static final MobileAdTargetingInfo targetingInfo = MobileAdTargetingInfo(
    keywords: ['Games', 'Puzzles'],
  );

  BannerAd bannerAd;
  InterstitialAd interstitialAd;
  RewardedVideoAd rewardedVideoAd;

  BannerAd buildBanner() {
    return BannerAd(
        adUnitId: BannerAd.testAdUnitId,
        size: AdSize.banner,
        listener: (MobileAdEvent event) {
          print(event);
        });
  }

  InterstitialAd buildInterstitial() {
    return InterstitialAd(
        adUnitId: InterstitialAd.testAdUnitId,
        targetingInfo: targetingInfo,
        listener: (MobileAdEvent event) {
          if (event == MobileAdEvent.failedToLoad) {
            interstitialAd..load();
          } else if (event == MobileAdEvent.closed) {
            interstitialAd = buildInterstitial()..load();
          }
          print(event);
        });
  }
  TargetPlatform _platform;
  VideoPlayerController _controller;

  @override
  void initState() {
    super.initState();
    _controller = new VideoPlayerController.network(
      'https://github.com/flutter/assets-for-api-docs/blob/master/assets/videos/butterfly.mp4?raw=true',
    );
    FirebaseAdMob.instance.initialize(appId: FirebaseAdMob.testAppId);
    bannerAd = buildBanner()..load();
    interstitialAd = buildInterstitial()..load();
  }
  @override
  void dispose(){
    super.dispose();
    _controller.dispose();
  }

  @override
  Widget build(BuildContext context) {
    bannerAd ..load()..show(
      anchorOffset: 20.0,
      anchorType: AnchorType.top,
    );
    Future<bool> _onBackPressed() {
      if(counter<1){
        interstitialAd
          ..load()
          ..show();
        counter++;
      }
      else{bannerAd.dispose();
      Navigator.pop(context, true);
      }

    }
    return WillPopScope(
      child: Scaffold(
        appBar: new AppBar(
          title: new Text(widget.title),
        ),
        body: new Column(
          children: <Widget>[
            new Expanded(
              child: new Center(
                child: new Chewie(
                  _controller,
                  aspectRatio: 3 / 2,
                  autoPlay: true,
                  looping: true,
                ),
              ),
            ),

            new Row(
              children: <Widget>[
                new Expanded(
                  child: new FlatButton(
                    onPressed: () {
                      setState(() {
                        _platform = TargetPlatform.android;
                      });
                    },
                    child: new Padding(
                      child: new Text("Android controls"),
                      padding: new EdgeInsets.symmetric(vertical: 16.0),
                    ),
                  ),
                ),
                new Expanded(
                  child: new FlatButton(
                    onPressed: () {
                      setState(() {
                        _platform = TargetPlatform.iOS;
                      });
                    },
                    child: new Padding(
                      padding: new EdgeInsets.symmetric(vertical: 16.0),
                      child: new Text("iOS controls"),
                    ),
                  ),
                )
              ],
            )
          ],
        ),
      ),
      onWillPop: _onBackPressed,
    );


  }
}

Answer 1

If you are facing issue at the time of 2 dialogs open on 1 screen.. Just put one dialogue in this Future.delayed...

Future.delayed(Duration.zero, () {
  Navigator. ...
});

Answer 2

An onPressed or onTap listener of a button that opens a dialog must be causing this. Simply add onPressed: () { myFunction(); ) onPressed: () { myFunction(); ) .This was something that worked for like a charm for me.

Answer 3

when i had experienced this useless error text it was because of screen root widget had no defined / finite size, i had at the root a "SingleChildScrollView",

to solve this i simply wrapped it in Container and set the height to screen max height like this:

  @override
  Widget build(BuildContext context) {
    return Container(
      height: MediaQuery.of(context).size.height,
      child: SingleChildScrollView(
        child: ...
      ),
    ),
  }

Answer 4

I believe that when implementing dispose() method, super.dispose(); should be called as last command.

Answer 5

try declaring the onPressed as below:

onPressed: () => your_func(),

Answer 6

try removing the recent piece of code you have edited before reloading the emulator. Refresh and if it works then try to improve the piece of code causing the error.

Note: Remember to Restart the app before loading.

Answer 7

My answer may not be a suitable answer to this question. But I experienced the same issue when I tried to show two flush bars and tried to navigate to a screen simultaneously. I solved the problem by removing the two flush bars, as I do not require those for my navigation.

Happy Coding !!!