如何在flutter中查看应用程序是否在后台最小化？

import 'package:flutter/widgets.dart';

class AppStateListener extends WidgetsBindingObserver {
  bool isAppInForeground = true;

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    switch (state) {
      case AppLifecycleState.resumed:
        isAppInForeground = true;
        // 应用程序从后台切换到前台
        break;
      case AppLifecycleState.inactive:
      case AppLifecycleState.paused:
      case AppLifecycleState.detached:
        isAppInForeground = false;
        // 应用程序进入后台
        break;
    }
  }
}

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  var appStateListener = AppStateListener();
  WidgetsBinding.instance.addObserver(appStateListener);
  runApp(MyApp());
}

if (appStateListener.isAppInForeground) {
  // 应用程序在前台
} else {
  // 应用程序在后台
}