flutter/Dart : A TextEditingController was used after being disposed

Question

拜托，有人帮忙解决这个问题，我不确定这是否是一个框架故障，那么怎么没有更多关于这个的帖子，如果是我那么为什么这个错误没有太多!

===========================主.dart

import 'package:flutter/material.dart';
import 'dialog_reusable.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          showDialog( context: context, builder: (context) { return MyDialog(); });
        },
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

===========================dialog_reusable.dart

import 'package:flutter/material.dart';

import 'dialog_reusable.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          showDialog( context: context, builder: (context) { return MyDialog(); });
        },
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

===========================

===========================

重现步骤

1. Textfield 是 Dialog() 的一部分，还有 2 个按钮“确定”和“取消”
2. 使用标准选项创建一个新的 Flutter 项目
3. 删除LIB文件夹中的文件
4. 使用上面提供的代码和名称制作新文件
5. 当 Dialog() 弹出并单击“取消”按钮时，会发生以下错误。

---

════════ 组件库捕获异常════════

构建 MouseRegion(监听器:[进入，退出]，状态:_MouseRegionState#1877d)抛出了以下断言:TextEditingController 被处置后使用。

一旦您在 TextEditingController 上调用了 dispose()，就不能再使用它。

导致错误的相关小部件是:TextField file:///C:/MobileApps/Apps/Clima-Flutter/lib/utilities/mydialog.dart:90:15

当抛出异常时，这是堆栈:

#0 ChangeNotifier._debugAssertNotDisposed。 (包:flutter/src/foundation/change_notifier.dart:106:9)

#1 ChangeNotifier._debugAssertNotDisposed(包:flutter/src/foundation/change_notifier.dart:112:6)

#2 ChangeNotifier.removeListener (package:flutter/src/foundation/change_notifier.dart:167:12)

#3 _AnimatedState.didUpdateWidget(包:flutter/src/widgets/transitions.dart:159:28)

#4 StatefulElement.update (package:flutter/src/widgets/framework.dart:4690:58)

---

尝试的步骤:

1. 在 Dispose() 之前使用文本字段的“启用”属性中的变量禁用文本字段
2. 如果在 Dispose() 之前保存 TextField 启用属性的变量为 false，则通过三元运算符和 if 子句将 NULL 分配给 TextField 的“Controller”属性
3. 如果在 Dispose() 之前保存 TextField 启用属性的变量为 false，则通过三元运算符和 if 子句将 NULL 分配给 TextField 的“onChanged:”属性

Answer 1

为防止出现错误 Flutter/Dart: A TextEditingController was used after being disposed，不应再次使用先前处置的 TextEditingController。您可以在此处执行的一种方法是传递一个新的 TextEditingController 实例以在 AlertDialog 中使用，或者取决于您如何使用 TextEditingController。

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  var textEditingController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Text(
            'You have entered ${textEditingController.text}',
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => alertDialog(textEditingController),
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }

  alertDialog(TextEditingController textEditingController) {
    return showDialog<String>(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          content: TextField(
            controller: textEditingController,
            decoration: const InputDecoration(hintText: 'Enter Something'),
          ),
          actions: <Widget>[
            TextButton(
              child: const Text(
                "Cancel",
                style: TextStyle(color: Colors.black),
              ),
              onPressed: () => Navigator.of(context).pop(),
            ),
            TextButton(
              child: const Text(
                "OK",
                style: TextStyle(color: Colors.red),
              ),
              onPressed: () {
                setState(() {
                  // Triggers a Widget rebuild to update textEditingController state
                });
                Navigator.of(context).pop();
              },
            ),
          ],
        );
      },
    );
  }
}