tasks.js

import * as BackgroundFetch from 'expo-background-fetch';
import * as TaskManager from 'expo-task-manager';

export async function registerFetchTask(FETCH_TASKNAME, runBackgroundSaga, INTERVAL) {
    TaskManager.defineTask(FETCH_TASKNAME, runBackgroundSaga);

    const status = await BackgroundFetch.getStatusAsync();
    switch (status) {
        case BackgroundFetch.Status.Restricted:
        case BackgroundFetch.Status.Denied:
            console.log("Background execution is disabled");
            return;

        default: {
            console.debug("Background execution allowed");

            let tasks = await TaskManager.getRegisteredTasksAsync();
            if (tasks.find(f => f.taskName === FETCH_TASKNAME) == null) {
                console.log("Registering task");
                await BackgroundFetch.registerTaskAsync(FETCH_TASKNAME, {
                    minimumInterval: INTERVAL,
                    stopOnTerminate: false,
                    startOnBoot: true
                },).then(() => BackgroundFetch.setMinimumIntervalAsync(INTERVAL));

                tasks = await TaskManager.getRegisteredTasksAsync();
                console.debug("Registered tasks", tasks);
            } else {
                console.log(`Task ${FETCH_TASKNAME} already registered, skipping`);
            }
        }
    }
}