颤音：`setState（）`当屏幕关闭时，还是如何检测屏幕是否打开？

Question

tldr：我有一个问题，如果有以下问题的答案：

1. 有没有办法可以检测到屏幕是否在EG

if (SCREEN IS ON) {
  setState(() {});  // i.e. update displayed widgets
}

2. 上setState（）这样，当屏幕关闭时，这就是完成吗？

更多详细信息：

我有一个播放音频的应用程序。屏幕打开时，小部件通过setState（）进行更新（例如，显示音频的进度）。尽管如此在完成setState（）代码之前。

因此，我希望确定我是否可以检测到setState（）在屏幕打开时，我可以在屏幕关闭时调用setState（）完成。

Answer 1

我将其用于Chatapp跟踪应用程序状态。我包裹着材料。通过一些更改，您可以做您想做的事。

import 'package:flutter/material.dart';
import 'package:flutter_stripe/flutter_stripe.dart';

import 'constants/credentials.dart';
import 'domain/repositories/my_user_repository.dart';

class AppLifeCycleManager extends StatefulWidget {
  final Widget child;
  final MyUserRepository myUserRepo;

  const AppLifeCycleManager(
      {Key? key, required this.child, required this.myUserRepo})
      : super(key: key);

  @override
  _AppLifeCycleManagerState createState() => _AppLifeCycleManagerState();
}

class _AppLifeCycleManagerState extends State<AppLifeCycleManager>
    with WidgetsBindingObserver {
  @override
  void initState() {
    super.initState();

    widget.myUserRepo.setOnlineCustomer();
    WidgetsBinding.instance.addObserver(this);
    // set the publishable key for Stripe - this is mandatory
    Stripe.publishableKey = pkTest;
  }

  @override
  Future<void> didChangeAppLifecycleState(AppLifecycleState state) async {
    super.didChangeAppLifecycleState(state);

    switch (state) {
      case AppLifecycleState.paused:
        widget.myUserRepo.setInactiveCustomer();
        break;
      case AppLifecycleState.resumed:
        widget.myUserRepo.setOnlineCustomer();
        break;
      case AppLifecycleState.inactive:
        widget.myUserRepo.setInactiveCustomer();
        break;
      case AppLifecycleState.detached:
        widget.myUserRepo.setInactiveCustomer();
        break;
    }
  }

  @override
  Widget build(BuildContext context) {
    return widget.child;
  }

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

Answer 2

安装可能是您想要的。另外，您可以检查 applifecyclestate href =“ https://api.flutter.dev/flutter/widgets/widgetsbindingobserver-class.html” rel =“ nofollow noreferrer”> widgetsbindingobserver 。

Answer 3

我尚未测试过，但是屏幕状态在酒吧中可能是您​​想要的。

Answer 4

非常感谢 @Mario-Francois，我得到了以下内容为我工作：

import 'package:flutter/material.dart';

class MyPage extends StatefulWidget {
  MyPage({Key? key}) : super(key: key);

  @override
  _MyPageState createState() => _MyPageState();
}

class _MyPageState extends State<MyPage> with WidgetsBindingObserver {
  bool screenOn = true;

  @override
  Future<void> didChangeAppLifecycleState(AppLifecycleState state) async {
    super.didChangeAppLifecycleState(state);
    switch (state) {
      case AppLifecycleState.paused:// screen off/navigate away
      // this.screenOn = false;
        break;
      case AppLifecycleState.resumed:  // screen on/navigate to
        this.screenOn = true;
        break;
      case AppLifecycleState.inactive:  // screen off/navigate away
        this.screenOn = false;
        break;
      case AppLifecycleState.detached:
        break;
    }
  }

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
  }

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

  @override
  Widget build(BuildContext context) {
    ...
  }
}