如何在 Flutter App 中处理 onPause/onResume? [英] How to handle onPause/onResume in Flutter App?

问题描述

我是 Dart/Flutter 的新手，想构建一个简单的应用，其中 LinearProgressBar 每秒更新一次.

I'm new to Dart/Flutter and would like to build a simple app where a LinearProgressBar gets updated every second.

在没有过多了解实际代码的情况下，我进行了以下设置.

Without getting too much into the actual code, I have the following setup working.

• 根据过去的时间计算进度的函数.
• 显示进度的 LinearProgressBar.
• 一个周期性的计时器，每秒重新计算进度并更新进度条.
• 我每次都调试打印 'tick'，重新计算就完成了.

一切都按预期进行，只有一个例外.当我在 Android 设备的后台移动应用程序时，勾号"不断被打印出来.

Everything is working as expected with one exception. The 'tick' keeps getting printed when I move the app in the background on my Android device.

在原生 Android 上，我会在触发 'onPause' 事件时取消我的定期计时器.

On native Android, I would cancel my periodic Timer when the 'onPause' event is triggered.

Flutter 中是否有类似的东西?我能找到的只有initState"和dispose".但是，将应用移至后台时不会调用 Dispose.

Is there something similar in Flutter? All I could find was 'initState' and 'dispose'. Dispose, however, does not get called when moving the app to background.

我不希望计时器在后台继续滴答作响.

I don't want the timer to keep ticking in the background.

在我的研究中，我发现了这个堆栈溢出问题 onresume-and-onpause-for-widgets-on-flutter.它的答案建议使用 TickerProviderStateMixin.

On my research, I found this Stack Overflow question onresume-and-onpause-for-widgets-on-flutter. It's answer suggests using TickerProviderStateMixin.

我是按照以下方式使用的.

I used it the following way.

class _BarItemState extends State<BarItem> with SingleTickerProviderStateMixin {
    Ticker ticker;
    num progress = 1.0;

    @override
    void initState() {
       super.initState();
       ticker = createTicker((duration) => setState(() {
          debugPrint('tick');
          progress = duration.inSeconds / 30;
       }))
      ..start();
    }

    // other stuff omitted

}

它正在工作，但我仍然不满意.

It is working, but I'm still not satisfied.

原因是，股票回调现在每隔几毫秒而不是每秒调用一次.在我看来，这像是在浪费资源(我不需要流畅的动画)，……我是不是把事情复杂化了?

The reason is, that the ticker callback is getting now called every few milliseconds instead of once a second. This seems to me like a waste of resources (I don't need a smooth animation), ... am I overcomplicating things?

即使看起来我的用例不需要它，我仍然想知道:

Even if it seems that I don't need it for my use case, I still would like to know:

如何自行处理 onPause/onResume 事件?

How to handle the onPause/onResume events on my own?

推荐答案

您可以覆盖WidgetBindingObserver接口的didChangeAppLifecycleState来接收应用生命周期的通知 变化.

You can override the didChangeAppLifecycleState of the WidgetBindingObserver interface to receive notifications for app lifecycle changes.

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