Flutter:在恢复时更新小部件? [英] Flutter: Update Widgets On Resume?

问题描述

在 Flutter 中，有没有办法在用户离开应用程序并立即返回时更新小部件?我的应用是基于时间的，尽快更新时间会很有帮助.

In Flutter, is there a way to update widgets when the user leaves the app and come right back to it? My app is time based, and it would be helpful to update the time as soon as it can.

推荐答案

你可以通过这样做来监听生命周期事件，例如:

You can listen to lifecycle events by doing this for example :

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

class LifecycleEventHandler extends WidgetsBindingObserver {
  final AsyncCallback resumeCallBack;
  final AsyncCallback suspendingCallBack;

  LifecycleEventHandler({
    this.resumeCallBack,
    this.suspendingCallBack,
  });

  @override
  Future<void> didChangeAppLifecycleState(AppLifecycleState state) async {
    switch (state) {
      case AppLifecycleState.resumed:
        if (resumeCallBack != null) {
          await resumeCallBack();
        }
        break;
      case AppLifecycleState.inactive:
      case AppLifecycleState.paused:
      case AppLifecycleState.detached:
        if (suspendingCallBack != null) {
          await suspendingCallBack();
        }
        break;
    }
  }
}



class AppWidgetState extends State<AppWidget> {
  void initState() {
    super.initState();

    WidgetsBinding.instance.addObserver(
      LifecycleEventHandler(resumeCallBack: () async => setState(() {
        // do something
      }))
    );
  }
  ...
}

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