异步任务在WorkManager的CallbackDispatcher中无法正常工作。

Question

我正在使用WorkManager进行后台服务。我的代码如下：

void callbackDispatcher() {
  Workmanager.executeTask((task, inputData) async {
    switch (task) {
      case "uploadLocalData":
        print("this method was called from background!");
        await BackgroundProcessHandler().uploadLocalData();
        print("background Executed!");
        return true;
       
        break;
      case Workmanager.iOSBackgroundTask:
        print("iOS background fetch delegate ran");
        return true;
        break;
    }
    return false;
   
  });
}

有没有办法在executeTask中等待异步方法？

- Raksha Deshmukh

Answer 1

通过完成器来实现非异步事物的异步化。您可以创建一个完成器，等待其未来并在未来中完成它。

Completer uploadCompleter = Completer();

void callbackDispatcher() {
  Workmanager.executeTask((task, inputData) async {
    switch (task) {
      case "uploadLocalData":
        print("this method was called from background!");
        await BackgroundProcessHandler().uploadLocalData();
        print("background Executed!");
        uploadCompleter.complete();
        return true;
       
        break;
      case Workmanager.iOSBackgroundTask:
        print("iOS background fetch delegate ran");
        return true;
        break;
    }
    return false;
   
  });
}

// somewhere else
await uploadCompleter.future;

- Gazihan Alankus

---

刚刚在uploadCompleter.complete();上面添加了await uploadCompleter.future;，这对我来说完美地解决了问题。谢谢 @GazihanAlankus - undefined

我很高兴能帮到你，但是我不明白 :) 如果在uploadCompleter.complete();之前等待uploadCompleter.future;，它永远不会执行到uploadCompleter.complete();，对吗？ - undefined

我也很震惊，因为从概念上来说是错误的，但对我来说却起作用了。 - undefined