相关使用可以参考网上，这里不在阐述，说下遇到的一个文件，就是flutter页面调原生方法关闭时，flutter页面没有走dispose方法。
解决办法：
1、调原生方法关闭时，先执行下flutter的路由关闭

Navigator.pop(context);

2、flutter MyAppWIdget 中定义一个变量isDetached， build方法里面，根据isDetached返回特定widget

main(List<String> args) async {
  runApp(const MyApp());
}

class MyApp extends StatefulWidget {
  final bool isDetached;

  const MyApp({
    Key? key,
    this.isDetached = false,
  }) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> with WidgetsBindingObserver {
  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    super.didChangeAppLifecycleState(state);

    switch (state) {
      case AppLifecycleState.detached:
        // 相关处理参考
        // https://github.com/flutter/flutter/pull/137957
        runApp(const MyApp(isDetached: true));
        // 清除内存中的图片缓存
        // https://github.com/Baseflow/flutter_cached_network_image/issues/429
        final imageCache = PaintingBinding.instance.imageCache;
        imageCache.clear();
        imageCache.clearLiveImages();
        break;
      default:
    }
  }

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    if (widget.isDetached) {
      // 引擎被detach, 移除所有的widget, 以此来及时释放资源
      Widget resultWidget = const SizedBox.shrink();
      // Fix report no OKToast widget found.
      // resultWidget = OKToast(child: resultWidget);
      return resultWidget;
    }
    return MaterialApp(
      ...
    );
  }
}

来源：https://juejin.cn/post/7344571292353790015