Flutter ScreenState Dispose方法异常 [英] Flutter ScreenState Dispose method exception

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本文介绍了Flutter ScreenState Dispose方法异常的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

当我尝试从一个屏幕导航移到另一个屏幕时，我得到一个异常，指出我要离开的ScreenState在其<屏幕中未调用 super.dispose()code> dispose 方法.但是，重写的 dispose 方法显然会调用 super.dispose().

When I try to navigate away from one screen to another in flutter, I am getting an exception stating that the ScreenState that I am changing away from does not call super.dispose() in its dispose method. However, the overriden dispose method clearly calls super.dispose().

随附的是相关的类和日志.任何帮助将不胜感激.

Attached are the relevant class and the logs. Any help would be greatly appreciated.

班级:

import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';
import 'package:kickit/screens/feed_screen.dart';
import 'package:kickit/screens/profile_screen.dart';
import 'package:kickit/screens/talk_screen.dart';
import 'package:kickit/utils/values/internal_strings.dart';
import 'package:kickit/utils/values/strings.dart';
import 'package:kickit/utils/values/values.dart';

/// Main screen that contains three screens within for displaying information.
/// Contains a:
/// - [TalkScreen]
/// - [FeedScreen]
/// - [ProfileScreen]
class MainScreen extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return new _MainScreenState();
  }
}

/// Manages the state of [MainScreen].
class _MainScreenState extends State<MainScreen> with ChangeNotifier {
  // A PageController to manage which screen is currently shown.
  PageController _pageController;

  // The current page that is in focus.
  // - 0 => ConversationScreen
  // - 1 => FeedScreen
  // - 2 => ProfileScreen
  int _page = 1;

  /// Initializes this [MainScreen], setting the initial screen to the
  /// [FeedScreen] due to [_page] starting at 1.
  @override
  void initState() {
    super.initState();
    _pageController = new PageController(
      initialPage: _page,
    );
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      // key: new ValueKey(InternalStrings.mainScaffoldKey),
      appBar: _appBar(),
      body: _mainScreens(),
      bottomNavigationBar: _bottomBar(),
    );
  }

  /// Gets an [AppBar] that will be shown across all of the screens controlled
  /// by this [MainScreen]
  AppBar _appBar() {
    return new AppBar(
      // key: new ValueKey(InternalStrings.mainAppBarKey),
      centerTitle: true,
      title: new Text(
        Strings.title,
        style: Theme.of(context).textTheme.title,
      ),
      actions: <Widget>[
        new IconButton(
          key: new ValueKey(InternalStrings.mainSettingsButtonKey),
          icon: new Icon(Icons.settings),
          onPressed: () => Navigator
              .of(context)
              .pushReplacementNamed(InternalStrings.mainScreenRoute),
        ),
      ],
    );
  }

  /// Gets a [PageView] storing the screens controlled by this [MainScreen].
  PageView _mainScreens() {
    return new PageView(
      // key: new ValueKey(InternalStrings.mainPageViewKey),
      controller: _pageController,
      onPageChanged: _onPageChanged,
      children: <Widget>[
        new Container(
          child: new TalkScreen(),
        ),
        new Container(
          child: new FeedScreen(),
        ),
        new Container(
          child: new ProfileScreen(),
        ),
      ],
    );
  }

  /// Gets a [BottomNavigationBar] that will be shown across all of the screens
  /// controlled by this [MainScreen]
  BottomNavigationBar _bottomBar() {
    return new BottomNavigationBar(
      // key: new ValueKey(InternalStrings.mainBottomBarKey),
      items: [
        new BottomNavigationBarItem(
          icon: new Icon(Icons.people),
          title: new Text(Strings.mainBottomBarTalk),
        ),
        new BottomNavigationBarItem(
          icon: new Icon(Icons.list),
          title: new Text(Strings.mainBottomBarFeed),
        ),
        new BottomNavigationBarItem(
          icon: new Icon(Icons.person),
          title: new Text(Strings.mainBottomBarProfile),
        ),
      ],
      onTap: _onNavigationTap,
      currentIndex: _page,
    );
  }

  /// Handles a tap on the bottom navigation bar.
  void _onNavigationTap(int page) {
    _pageController.animateToPage(
      page,
      duration: Values.animationShort,
      curve: Curves.ease,
    );
  }

  /// Handles a page change and updates the bottom bar.
  void _onPageChanged(int page) {
    this._pageController.notifyListeners();
    setState(() {
      this._page = page;
    });
  }

  /// Dispose of the [PageController] when disposed.
  @override
  void dispose() {
    super.dispose();
    _pageController.dispose();
  }
}

日志:

I/flutter (18130): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (18130): The following assertion was thrown while finalizing the widget tree:
I/flutter (18130): MainScreenState.dispose failed to call super.dispose.
I/flutter (18130): dispose() implementations must always call their superclass dispose() method, to ensure that all the
I/flutter (18130): resources used by the widget are fully released.
I/flutter (18130): 
I/flutter (18130): When the exception was thrown, this was the stack:
I/flutter (18130): #0      StatefulElement.unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:3771)
I/flutter (18130): #1      StatefulElement.unmount (package:flutter/src/widgets/framework.dart:3776)
I/flutter (18130): #2      _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1670)
I/flutter (18130): #3      _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #4      ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3644)
I/flutter (18130): #5      _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #6      _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #7      ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3644)
I/flutter (18130): #8      _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #9      _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #10     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4584)
I/flutter (18130): #11     _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #12     _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #13     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4584)
I/flutter (18130): #14     _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #15     _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #16     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4584)
I/flutter (18130): #17     _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #18     _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #19     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3644)
I/flutter (18130): #20     _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #21     _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #22     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3644)
I/flutter (18130): #23     _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #24     _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #25     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4584)
I/flutter (18130): #26     _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #27     _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #28     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4584)
I/flutter (18130): #29     _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #30     _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #31     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3644)
I/flutter (18130): #32     _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #33     _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #34     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4584)
I/flutter (18130): #35     _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #36     _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #37     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3644)
I/flutter (18130): #38     _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #39     _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #40     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3644)
I/flutter (18130): #41     _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #42     _InactiveElements._unmount.<anonymous closure> (package:flutter/src/widgets/framework.dart:1668)
I/flutter (18130): #43     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3644)
I/flutter (18130): #44     _InactiveElements._unmount (package:flutter/src/widgets/framework.dart:1666)
I/flutter (18130): #45     ListIterable.forEach (dart:_internal/iterable.dart:39)
I/flutter (18130): #46     _InactiveElements._unmountAll (package:flutter/src/widgets/framework.dart:1679)
I/flutter (18130): #47     BuildOwner.finalizeTree.<anonymous closure> (package:flutter/src/widgets/framework.dart:2296)
I/flutter (18130): #48     BuildOwner.lockState (package:flutter/src/widgets/framework.dart:2128)
I/flutter (18130): #49     BuildOwner.finalizeTree (package:flutter/src/widgets/framework.dart:2295)
I/flutter (18130): #50     BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:623)
I/flutter (18130): #51     BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:208)
I/flutter (18130): #52     BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990)
I/flutter (18130): #53     BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930)
I/flutter (18130): #54     BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:842)
I/flutter (18130): #55     _invoke (file:///b/build/slave/Linux_Engine/build/src/flutter/lib/ui/hooks.dart:120)
I/flutter (18130): #56     _drawFrame (file:///b/build/slave/Linux_Engine/build/src/flutter/lib/ui/hooks.dart:109)
I/flutter (18130): ════════════════════════════════════════════════════════════════════════════════════════════════════
Application finished.

推荐答案

我找到了一个临时解决方法.经过进一步检查，我的 dispose 方法正在调用 ChangeNotifier mixin的 dispose 方法，而不是 State< T> 课.

I have found a temporary workaround. Upon further inspection my dispose method was calling the dispose method of the ChangeNotifier mixin rather than the State<T> class.

我可以通过从班级中删除 ChangeNotifier mixin来解决此问题.如果有人知道如何解决此问题而又不摆脱 ChangeNotifier 混用的情况，那么我相信这将是一个更好的解决方案.

I was able to get rid of this issue by removing the ChangeNotifier mixin from my class. If anyone knows how to solve this issue without getting rid of the ChangeNotifier mixing, I'm sure that would be a better solution.

这篇关于Flutter ScreenState Dispose方法异常的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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