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简介：我花了一个多小时浏览 StackOverflow 来寻找这个答案；所以，我犹豫地决定问这个我认为没有答案的问题。我希望它不会重复已经回答的问题，令人作呕。

在过去的五周里，我一直沉浸在 BLoC 模式的研究中（是的，我知道我落后于曲线大约一年）。我一直在观看几个视频并阅读有关该主题的几本书。我了解到，如果没有调用 dispose 方法，就会发生内存泄漏。在我最近观看的许多 YouTube 视频中，建议使用有状态小部件而不是无状态小部件，以便可以在应用程序的生命周期中使用 dispose 方法来防止内存泄漏。

问题：通过Provide.of 方法安置继承的小部件以获得有状态小部件的上下文范围的正确方法是什么，因此可以在生命周期中使用dispose（）方法？

相关代码：

import 'package:flutter/material.dart';

import 'package:testingblock6/counter_provider.dart';
import 'counter_event.dart';
import 'model.dart';

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  @override
  Widget build(BuildContext context) {
    final _bloc = Provider.of(context);

    return Scaffold(
      appBar: AppBar(
        title: Text('Testing Bloc 6'),
      ),
      body: Center(
          child: StreamBuilder<Model>(
        stream: _bloc.modelStream,
        initialData: Model(),
        builder: (BuildContext context, AsyncSnapshot<Model> snapshot) {
          return Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text(
                'You have pushed the button this many times:',
              ),
              Text(
                'Counter: ${snapshot.data.counter}',
                style: Theme.of(context).textTheme.display1,
              ),
              Text(
                'ThisGuy: ${snapshot.data.thisGuy}',
                style: Theme.of(context).textTheme.display1,
              ),
            ],
          );
        },
      )),
      floatingActionButton: Row(
        mainAxisAlignment: MainAxisAlignment.end,
        children: <Widget>[
          FloatingActionButton(
            onPressed: () => _bloc.counterEventSink.add(IncrementEvent()),
            tooltip: 'Increment',
            child: Icon(Icons.add),
          ),
          SizedBox(width: 10),
          FloatingActionButton(
            onPressed: () => _bloc.counterEventSink.add(DecrementEvent()),
            tooltip: 'Decrement',
            child: Icon(Icons.remove),
          ),
          SizedBox(width: 10),
          FloatingActionButton(
            onPressed: () => _bloc.counterEventSink.add(ThisGuy()),
            tooltip: 'ThisGuy',
            child: Icon(Icons.golf_course),
          ),
        ],
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }

  @override
  void dispose() {
    super.dispose();
    // _bloc.dispose();
  }
}

问题：我认为必须在代码的 _HomeState 区域内调用 Provider.of 方法，因为这是上下文可用的地方。但是，通过这样做，它会将其从 dispose 方法的范围中删除。

问题：关于 dispose() 方法范围的可用性，我做错了什么，有没有我没有看到的答案？

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1 回答 1

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import 'package:flutter/material.dart';

import 'counter_event.dart';
import 'counter_provider.dart';
import 'model.dart';

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  var _bloc;

  @override
  Widget build(BuildContext context) {
    _bloc = Provider.of(context);

    return Scaffold(
      appBar: AppBar(
        title: Text('Testing Bloc 6'),
      ),
      body: Center(
          child: StreamBuilder<Model>(
        stream: _bloc.modelStream,
        initialData: Model(),
        builder: (BuildContext context, AsyncSnapshot<Model> snapshot) {
          return Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text(
                'You have pushed the button this many times:',
              ),
              Text(
                'Counter: ${snapshot.data.counter}',
                style: Theme.of(context).textTheme.display1,
              ),
              Text(
                'ThisGuy: ${snapshot.data.thisGuy}',
                style: Theme.of(context).textTheme.display1,
              ),
            ],
          );
        },
      )),
      floatingActionButton: Row(
        mainAxisAlignment: MainAxisAlignment.end,
        children: <Widget>[
          FloatingActionButton(
            onPressed: () => _bloc.counterEventSink.add(IncrementEvent()),
            tooltip: 'Increment',
            child: Icon(Icons.add),
          ),
          SizedBox(width: 10),
          FloatingActionButton(
            onPressed: () => _bloc.counterEventSink.add(DecrementEvent()),
            tooltip: 'Decrement',
            child: Icon(Icons.remove),
          ),
          SizedBox(width: 10),
          FloatingActionButton(
            onPressed: () => _bloc.counterEventSink.add(ThisGuy()),
            tooltip: 'ThisGuy',
            child: Icon(Icons.golf_course),
          ),
        ],
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }

  @override
  void dispose() {
    super.dispose();
    _bloc.dispose();
  }
}
于 2020-04-04T00:29:59.083 回答