Flutter-TabBarView-KeepAlive

main.dart

import 'package:flutter/material.dart';

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> {
  final indexes = List.generate(10, (index) => index);

  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
      length: indexes.length,
      child: Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
          bottom: TabBar(
            isScrollable: true,
            tabs: [
              for (var i in indexes)
                Tab(text: 'tab$i'),
            ],
          ),
        ),
        body: TabBarView(
          children: [
            ...indexes.map((i) {
              return i % 2 == 0 ? PlainWidget(i: i) : AliveWidget(i: i);
            })
          ],
        ),
      ),
    );
  }
}

class PlainWidget extends StatelessWidget {
  const PlainWidget({
    Key? key,
    required this.i,
  }) : super(key: key);

  final int i;

  @override
  Widget build(BuildContext context) {
    debugPrint('PlainWidget build $i');
    return Center(
      child: Text('PlainWidget$i'),
    );
  }
}

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

  final int i;

  @override
  State<StatefulWidget> createState() => AliveWidgetState();
}

class AliveWidgetState extends State<AliveWidget> with AutomaticKeepAliveClientMixin {
  @override
  bool get wantKeepAlive => true;

  @override
  Widget build(BuildContext context) {
    super.build(context);

    debugPrint('AliveWidget build ${widget.i}');
    return Center(
      child: Text('AliveWidget${widget.i}'),
    );
  }
}