index.js

/**
 * @format
 */

import { AppRegistry } from 'react-native';
import App from './App';
import { name as appName } from './app.json';

import BackgroundGeolocation from "react-native-background-geolocation";

// [Android-only] See API docs Config.enableHeadless.  This method MUST exist here in index.js.
// An Android Headless Task will receive all events emitted by the background-geolocation plugin while
// your app is terminated.
//
const bgGeoHeadlessTask = async (event) => {
  const params     = event.params; // <-- our event-data from the BG Geo SDK.
  const eventName  = event.name;
  const taskId     = event.taskId; // <-- very important!

  console.log(`[BGGeoHeadlessTask] ${eventName}`, JSON.stringify(params));
  // You MUST await your work!
  // HeadlessTasks are automatically terminated after execution of the last line of your function.
  await doWork(eventName);
}

BackgroundGeolocation.registerHeadlessTask(bgGeoHeadlessTask);

///
/// A stupid little "long running task" simulator for headless-tasks.
/// Uses a simple JS setTimeout timer to simulate work.
///
let doWorkCounter = 0;

const doWork = async (eventName) => {
  return new Promise(async (resolve, reject) => {
    if (eventName == 'terminate') {
      doWorkCounter = 0;
      // Perform a weird action (for testing) with an interval timer and .startBackgroundTask.
      const bgTaskId = await BackgroundGeolocation.startBackgroundTask();
      // Print * tick * to log every second.
      const timer = setInterval(() => {
        console.log(`[BGGeoHeadlessTask *][doWork] * tick ${++doWorkCounter}/10 *`);
      }, 1000);
      // After 10s, stop the interval and stop our background-task.
      setTimeout(() => {
        clearInterval(timer);
        BackgroundGeolocation.stopBackgroundTask(bgTaskId);
        resolve();
      }, 10000);

    } else {
      // do nothing
      console.log('[BGGeoHeadlessTask *][doWork]', eventName);
      resolve();
    }
  });
}

AppRegistry.registerComponent(appName, () => App);