flutter的AutomaticKeepAliveClientMixin在navigator.push后不保持页面状态

Question

在测试AutomaticKeepAliveClientMixin并遇到问题，在navigator.push后页面丢失状态。有人知道此问题吗？任何解决方法？为任何信息而高兴，欢呼

我的目标是保持页面状态

重现步骤：打开应用程序，单击PageOne的按钮，然后向左和向右滑动，页面将丢失状态 图像

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(home: MyApp()));

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: DefaultTabController(
        initialIndex: 0,
        length: 2,
        child: Scaffold(
          body: TabBarView(
            children: <Widget>[Page1(), Page2()],
          ),
          bottomNavigationBar: Material(
            child: TabBar(
              labelColor: Colors.black,
              tabs: <Widget>[
                Tab(
                  icon: Icon(Icons.check),
                ),
                Tab(
                  icon: Icon(Icons.check),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

class Page1 extends StatefulWidget {
  @override
  Page1State createState() {
    return new Page1State();
  }
}

class Page1State extends State<Page1> with AutomaticKeepAliveClientMixin {
  @override
  Widget build(BuildContext context) {
    return ListView(
      children: <Widget>[
        Container(
          height: 300,
          color: Colors.orange,
        ),
        Container(
          height: 300,
          color: Colors.pink,
        ),
        Container(
          height: 300,
          color: Colors.yellow,
          child: Center(
            child: Container(height: 26,
              child: MaterialButton(
                  color: Colors.blue,
                  child:
                      Text('clicking this and back then swipe => page loses state'),
                  onPressed: () {
                    Navigator.push(
                      context,
                      MaterialPageRoute(builder: (context) => PushedPage()),
                    );
                  }),
            ),
          ),
        ),
      ],
    );
  }

  @override
  bool get wantKeepAlive => true;
}

class Page2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(height: 300, color: Colors.orange);
  }
}

class PushedPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Container(
        color: Colors.blue,
      ),
    );
  }
}

Answer 1

从AutomaticKeepAliveClientMixin的文档中：

///为[AutomaticKeepAlive]的客户提供了具有便捷方法的混合。与[State]子类一起使用。

///子类必须实现[wantKeepAlive]，并且它们的[build]方法必须调用super.build（返回值始终返回null，应将其忽略）。

因此，在您的代码中，在返回ListView之前，只需调用super.build：

  Widget build(BuildContext context) {
    super.build(context);
    return ListView(..
  }