❓How to schedule a Periodic Task

[kterto]

I've been trying to use the package, but I couldn't find out where to put the code to perform the desired Task. As I understood from the working example and from the plugin implementation, I would have to write a custom class that extends the Worker and override the doWork function, but when installing the package by pubspec I wasn't able to find out where to put it.

[timrijckaert]

Hi @kterto, 👋

Thanks for checking out this package.
You are actually the first to open up an issue.

The background job you wish to execute should be written in Dart, you do not need to do any native work to make it work.
Could you describe your use case, so I can understand it better?

[kterto]

Hi, @timrijckaert, that's my use case:
I would like to perform Firebase requests periodically to check data with the app not executing and trigger an alarm when some condition is met and wake the app.
Thank's for the reply.

[timrijckaert]

Alright, you would want to do something like this:

Define a top level function lets call it callbackDispatcher here, but you could name it whatever you want.
This function will be called in the background.

You need to return either true or false.
Whether your Firebase syncing was successful or not.

void callbackDispatcher() {
  Workmanager.defaultCallbackDispatcher((task) {
    switch (task) {
      case "firebaseSyncing":
        print("sync with Firebase");
        break;
    }

    // Return whether the job ran successful or not.
    return Future.value(true);
  });
}

You then need to initialize the plugin with this function.
In your case you wish to have a task that runs every X time.
Therefore you use the Workmanager#registerPeriodicTask method to schedule a task that will run every X time.
You can configure the time and other constraints (please look in the README).

void main() {
  Workmanager.initialize(callbackDispatcher);
  Workmanager.registerPeriodicTask("1", "firebaseSyncing");
  runApp(MyApp());
}

Let me know if it works.

[kterto]

Ok, I've been doing something like what you've just said, but where I define the action? Where am I supposed to write the body of the actual function firebaseSyncing that I want to run in the background?

[timrijckaert]

print("sync with Firebase");

[kterto]

Now the problem is said to be that executeTask is not implemented in the Workmanager.

[timrijckaert]

You are correct, I was referencing the upcoming v0.0.7 API this library.
I corrected the original answer to reflect the required method for v0.0.6 of the library.

[timrijckaert]

Does it work for you now?
Can this be closed?

[kterto]

I had a problem in the machine and I had to restart... But it's not working yet.
E/MethodChannel#be.tramckrijte.workmanager/foreground_channel_work_manager( 3529): Failed to handle method call

[timrijckaert]

You are most likely running the app on an iOS simulator?
Version v0.0.6 will only work for Android. Therefore you should wrap your calls to check if it runs on Android.

if (Platform.isAndroid) {
  Workmanager.initialize(callbackDispatcher);
  Workmanager.registerPeriodicTask("1", "firebaseSyncing");
}

We are currently working on implementing iOS support in an upcoming version.

Let me know if it works.

[kterto]

Actually I'm running in my android Mobile, not in a simulator. I've wrapped the code in the if statement and still not working.

[timrijckaert]

Could you send me the code please

[kterto]

That's what I'm trying to do:

main.txt

[timrijckaert]

Yes I see we have a small bug.
Thanks for reporting this, we will fix it in the upcoming release.
For now you should set the isInDebugMode flag.

void main() async {
  if (Platform.isAndroid) {
    Workmanager.initialize(callbackDispatcher, isInDebugMode: true);
    Workmanager.registerPeriodicTask("1", "firebaseSyncing");
  }
  runApp(App());
}

[kterto]

outcome with the isInDebugMode flag:
debugMode.txt

[timrijckaert]

I/flutter ( 6599): syncing with Firebase
I/WM-WorkerWrapper( 6599): Worker result SUCCESS for Work [ id=a54cb75b-569b-45b5-807f-5c4346129bc0, tags={ be.tramckrijte.workmanager.EchoingWorker } ]

It worked!
Congratz 😄

The native crash underneath is not caused by the plugin.

[kterto]

If I run without the isInDebugMode flag, I still get an error. Is there any way of running in debug mode and not showing the system notification?

[timrijckaert]

You could set the isInDebugMode to false that would work.

I also just updated the plugin to version v0.0.6+1, it fixes the bug.
With v0.0.6+1 you don't need to explicitly set the isDebugMode flag no more.

Workmanager.initialize(callbackDispatcher);

[kterto]

(sorry to keep reopening this issue, should I use another one?)
Well, when trying to call another plugins, like the firebase_auth, in the callbackDispatcher, I've been facing a problem related to the plugins's own methodChannel... so using functions are not working.
So far I've just succeeded printing to the console some message. I've tried using a local plugin too that I had started just to access native alarm sound and trigger it, it works alone, but in integration with Workmanager it doesn't.
The errors are like this:
[ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: MissingPluginException(No implementation found for method FirebaseApp#appNamed on channel plugins.flutter.io/firebase_core)

[timrijckaert]

I just tested myself with a simple plugin path_provider and I have the same issue.
Seems there is a bug when using background tasks in combination with plugins.

It's better to open up a different issue as this is totally separate bug.
I wonder if it is similar to this issue

[AxesandGrinds]

Was there a solution to this? Are method calls not working in workmanager?