Android后退按钮关闭应用程序而不是弹出当前路线

Question

在我的 Flutter 应用程序中使用新的 Navigator 2.0 API 进行导航，我的代码具有以下简单版本：

import 'package:flutter/material.dart';

void main() {
  runApp(const MainApp());
}

class MainApp extends StatelessWidget {
  const MainApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Router(
        routerDelegate: AppRouterDelegate(),
        backButtonDispatcher: RootBackButtonDispatcher(),
      ),
    );
  }
}

class MainPage extends StatelessWidget {
  const MainPage({super.key, required this.openFirstPage});

  final VoidCallback openFirstPage;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Main page'),
        backgroundColor: Colors.lightGreen,
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text('Welcome to main page!'),
            ElevatedButton(
              onPressed: openFirstPage,
              child: const Text('Go to first page'),
            ),
          ],
        ),
      ),
    );
  }
}

class FirstPage extends StatelessWidget {
  const FirstPage({super.key, required this.openSecondPage});

  final VoidCallback openSecondPage;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('First page'),
        backgroundColor: Colors.amber,
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text('Welcome to first page!'),
            ElevatedButton(
              onPressed: openSecondPage,
              child: const Text('Go to second page'),
            ),
          ],
        ),
      ),
    );
  }
}

class SecondPage extends StatelessWidget {
  const SecondPage({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Second page'),
        backgroundColor: Colors.lightBlueAccent,
      ),
      body: const Center(
        child: Text('Welcome to second page!'),
      ),
    );
  }
}

class AppRouterDelegate extends RouterDelegate
    with ChangeNotifier, PopNavigatorRouterDelegateMixin {
  bool _showFirstPage = false;
  void showFirstPage() {
    _showFirstPage = true;
    notifyListeners();
  }

  bool _showSecondPage = false;
  void showSecondPage() {
    _showSecondPage = true;
    notifyListeners();
  }

  @override
  Widget build(BuildContext context) {
    return Navigator(
      pages: [
        MaterialPage(
          key: const ValueKey('MainPage'),
          child: MainPage(openFirstPage: showFirstPage),
        ),
        if (_showFirstPage)
          MaterialPage(
            key: const ValueKey('FirstPage'),
            child: FirstPage(openSecondPage: showSecondPage),
          ),
        if (_showSecondPage)
          const MaterialPage(
            key: ValueKey('SecondPage'),
            child: SecondPage(),
          ),
      ],
      onDidRemovePage: (page) {
        if (_showSecondPage) {
          _showSecondPage = false;
          return;
        }
        if (_showFirstPage) _showFirstPage = false;
      },
    );
  }

  @override
  GlobalKey<NavigatorState>? get navigatorKey => GlobalKey();

  @override
  Future<void> setNewRoutePath(configuration) async {
    // Do nothing
  }
}

当点击

AppBar

中的后退按钮时，页面会按预期弹出（当前页面关闭并显示下面的页面）：

Second Page ---> pop ---
    |                  │
    |                  ↓
First Page        First Page ---> pop ---
    |                  |                │
    |                  |                ↓
Main Page          Main Page        Main Page

...，但是当按下/滑动 Android 后退按钮时，会关闭整个应用程序而不是当前页面。

Second Page ---> Android back btn pop ---
    |                                   │
    |                                   |
First Page                              |
    |                                   |
    |                                   ↓
Main Page                         App is closed

这是一个例子：

Answer 1

只需删除清单文件中的

android:enableOnBackInvokedCallback="true"