Flutter：滑动后默认选项卡栏控制器不保持状态 [英] Flutter: Default Tab Bar Controller does not maintain state after swipe

问题描述

我正在用flutter编写具有4个选项卡式视图的应用程序，有点像普通的android手机应用程序或时钟应用程序。这些视图之一散列了一个浮动操作按钮，按下该按钮将在列表中添加一些文本。但是，当我滚动到其他视图之一并返回时，所有文本都消失了。有解决办法吗？

I am writing an application in flutter that has 4 tabbed views, kinda like the stock android phone app or clock app. One of those views hash a floating action button that when pressed will add some text in a list. However, when I scroll to one of the other views and come back, all of the text is gone. Is there a way to fix this?

这是我的代码：

import 'package:flutter/material.dart';
import 'Screens/Dashboard.dart';
import 'Screens/CreateQuestionnaire.dart';
import 'Screens/AccountScreen.dart';

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

class MyApp extends StatefulWidget {
  @override
 createState() => new MyAppState();
}

class MyAppState extends State<MyApp> {
  final primaryColour = const Color(0xFF5CA1CA);
  final secondaryColour = const Color(0xFFC36B42);
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new DefaultTabController(
        length: 4,
        child: new Scaffold(
          appBar: new AppBar(
            actions: <Widget>[
              new IconButton(icon: new Icon(Icons.account_circle),
              onPressed: (){
                Navigator.push(context, new MaterialPageRoute(builder: (context) => new AccountScreen()));
              }),
            ],
            bottom: new TabBar(
              tabs: <Widget>[
                new Tab(icon: new Icon(Icons.home)),
                new Tab(icon: new Icon(Icons.contacts)),
                new Tab(icon: new Icon(Icons.description)),
                new Tab(icon: new Icon(Icons.settings))
              ],
            ),
            title: new Text("NLPro Questionnaire"),
          ),
          body: new TabBarView(
            children: <Widget>[
              new Dashboard(),
              new CreateQuestionnaire(),
              new Text("Surveys"),
              new Text("Settings")
            ],
          ),
        ),
      ),
      theme:new ThemeData(
        primaryColor: primaryColour,
        accentColor: secondaryColour,
      ),
    );
  }
}

在此处输入图片描述

推荐答案

您需要在有状态窗口小部件上使用 AutomaticKeepAliveClientMixin 并实现名为 wantKeepAlive

You need to use AutomaticKeepAliveClientMixin over your stateful widget and implement override method called wantKeepAlive

class MyApp extends StatefulWidget {
@override
createState() => new MyAppState();
}

将AutomaticKeepAliveClientMixin与您的类扩展状态和ov一起使用

use AutomaticKeepAliveClientMixin with your class extending state and ov

class MyAppState extends State<MyApp> with AutomaticKeepAliveClientMixin<MyApp>{

//your existing code.....

@override
bool get wantKeepAlive => true;   //by default it will be null, change it to true.

//your existing code......

}

在将wantKeepAlive设置为true时，initState方法在创建时将只运行一次。

on setting wantKeepAlive to true, initState method will run only once, at the time of creation.

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