Programming Tutorials

Start background location tracking after login in expo react native

By: Adeline in React-Native Tutorials on 2023-05-16  

If you want to have a background job in an expo app to get the location of the device continuously and the job should start only after login is successful. You can define the background task in app.js and then when login is successful in another component, (for example user.js) you can start the job.

To achieve this in an Expo app, you can follow these steps:

1. Install the required packages:

   npm install expo-location expo-task-manager
   

2. Set up the background task in your app.js file:

   import * as Location from 'expo-location';
   import * as TaskManager from 'expo-task-manager';
   
   // Define the task name
   const BACKGROUND_TASK_NAME = 'LOCATION_TASK';
   
   // Define the background task handler
   TaskManager.defineTask(BACKGROUND_TASK_NAME, async ({ data, error }) => {
     if (error) {
       console.error('Error in background task:', error);
       return;
     }
     if (data) {
       const { locations } = data;
       // Process the received locations here
       console.log('Received locations:', locations);
     }
   });
   
   // Request permission for location updates
   const requestLocationPermission = async () => {
     const { status } = await Location.requestForegroundPermissionsAsync();
     if (status === 'granted') {
       Location.startLocationUpdatesAsync(BACKGROUND_TASK_NAME, {
         accuracy: Location.Accuracy.Balanced,
       });
     }
   };
   
   // Call the permission function
   requestLocationPermission();
   

3. In your user.js component, start the background task after successful login:

   import * as TaskManager from 'expo-task-manager';
   
   // Define the same task name as in app.js
   const BACKGROUND_TASK_NAME = 'LOCATION_TASK';
   
   // Start the background task after successful login
   const startBackgroundTask = () => {
     TaskManager.isTaskRegisteredAsync(BACKGROUND_TASK_NAME).then((isRegistered) => {
       if (isRegistered) {
         TaskManager.getRegisteredTasksAsync().then((tasks) => {
           const backgroundTask = tasks.find((task) => task.taskName === BACKGROUND_TASK_NAME);
           if (backgroundTask) {
             TaskManager.startTaskAsync(BACKGROUND_TASK_NAME).then(() => {
               console.log('Background task started');
             });
           }
         });
       }
     });
   };
   
   // Call the function after successful login
   startBackgroundTask();
   

With this setup, the background task defined in app.js will continuously receive the device's location updates. The task will start running only after the user successfully logs in, triggered by the startBackgroundTask function in the user.js component. Make sure to handle any necessary cleanup or stopping of the task as per your requirements.