如何在Flutter的Scaffold.drawer中保持小部件的状态?

问题描述

我想将小部件的状态保持在Scaffold.drawer中. The Scaffold.drawer是自定义窗口小部件，其中具有 RaiseButton .当单击按钮时，按钮中的文本更改.但是当抽屉关闭后，重新打开抽屉时，更改后的文本将被重置.

I want to keep the widget's state in Scaffold.drawer. The Scaffold.drawer is a custom widget, which has a RaiseButton in it.When click the button, the text in the button changed.But when the drawer is closed, and reopen the drawer, the changed text is reseted.

我在自定义的 Drawer 中使用了"with AutomaticKeepAliveClientMixin<>"，但是它不起作用.

I have use " with AutomaticKeepAliveClientMixin<> " in my custom Drawer, but it does't work.

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

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

class _MyHomePageState extends State<MyHomePage> {

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Flutter Demo"),
      ),
      drawer: Drawer(child: CustomDrawer(),),
      body: Center(
        child: Text("Flutter Demo"),
      ),
    );
  }
}

class CustomDrawer extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _CustomDrawerState();
  }
}

class _CustomDrawerState extends State<CustomDrawer> with AutomaticKeepAliveClientMixin<CustomDrawer> {

  String btnText = "Click!";

  @override
  bool get wantKeepAlive => true;

  @override
  Widget build(BuildContext context) {
    super.build(context);
    return Center(
      child: RaisedButton(onPressed: () {
        setState(() {
          btnText = "Clicked!!";
        });
      }, child: Text(btnText),),
    );
  }

}

我希望即使关闭了抽屉，小部件的状态也可以保留.

I expect the widget's state can keep, even if the Drawer is closed.

推荐答案

在您的情况下，您有2个选择:

In your case, you have 2 choices:

1. 您应将状态保留在顶级"小部件中.就您而言_MyHomePageState;
2. 使用状态管理器，例如Redux，Bloc，ScopedModel.在这种情况下，我认为ScopedModel对您而言非常有用.

1. You should keep your state in your Top level widget. in your case _MyHomePageState;
2. Use state managers like Redux, Bloc, ScopedModel. I think ScopedModel is great for you in this case.

否则，您将无法控制Drawer的状态.导致每当您通过Appbar中的操作按钮调用Drawer时，它都会重新创建；

otherwise, you can't control the state of Drawer. cause it re-creates every moment you call the Drawer by the action button in Appbar;

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