OneOffTask

Schedule one-off tasks with OneOffTask.

What is OneOffTask?

OneOffTask represents a background task that runs once. It is registered with Workmanager().registerOneOffTask; the task runs once after a while. The first parameter is the task id and the second is the name passed to callbackDispatcher.

Workmanager().registerOneOffTask(
  'sync-task',
  'sync',
);

registerOneOffTask

The registerOneOffTask method schedules a one-time task. You tag the task with tag and provide a start delay with initialDelay. When the task runs, callbackDispatcher is called and the name in the second parameter arrives as task.

Workmanager().registerOneOffTask(
  'sync-task',
  'sync',
  initialDelay: Duration(seconds: 10),
);

Exercise Register a one-off task

Register a task with Workmanager().registerOneOffTask using id 'sync-task' and callback name 'sync', and print 'ok'.

Show example solution

class Workmanager {
  void initialize(Function dispatcher, {bool isInDebugMode = false}) {}
  void registerOneOffTask(String uniqueId, String taskName, {Duration? initialDelay}) {}
}

bool callbackDispatcher(String task) => true;

void main() {
  Workmanager().registerOneOffTask('sync-task', 'sync');
  print('ok');
}

Test yourself

How many times does OneOffTask run?
- Continuously, at fixed intervals
- Only once
- On every app launch
- Never runs
Show answer

Only once — OneOffTask runs only once; for periodic execution you use PeriodicTask.

Workmanager().____(
  'sync-task',
  'sync',
);

Show answer

Workmanager().registerOneOffTask(
  'sync-task',
  'sync',
);

OneOffTask parts

registerOneOffTask

One-off registration
'sync-task'

Task identifier
'sync'

Callback name
initialDelay

Initial delay

Next lesson: PeriodicTask

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