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Expo TaskManager

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A library that provides support for tasks that can run in the background.

expo-task-manager provides an API that allows you to manage long-running tasks, in particular those tasks that can run while your app is in the background. Some features of this library are used by other libraries under the hood. Here is a list of Expo SDK libraries that use TaskManager:

Platform Compatibility

Android Device	Android Emulator	iOS Device	iOS Simulator	Web

Installation

Terminal

- npx expo install expo-task-manager

If you are installing this in an existing React Native app, start by installing expo in your project. Then, follow the additional instructions as mentioned by the library's README under "Installation in bare React Native projects" section.

Configuration in app.json/app.config.js

Background modes on iOS

TaskManager works out of the box in the Expo Go app on Android. However, on iOS, you'll need to use a development build.

Standalone apps need some extra configuration: on iOS, each background feature requires a special key in UIBackgroundModes array in your Info.plist file. In standalone apps this array is empty by default, so to use background features you will need to add appropriate keys to your app.json configuration.

Here is an example of an app.json configuration that enables background location, background fetch and remote notifications:

app.json

{
  "expo": {
    "ios": {
      "infoPlist": {
        "UIBackgroundModes": ["location", "fetch", "remote-notification"]
      }
    }
  }
}

Are you using this library in a bare React Native app?

Learn how to configure the native projects in the installation instructions in the expo-task-manager repository.

Example

import React from 'react';
import { Button, View, StyleSheet } from 'react-native';
import * as TaskManager from 'expo-task-manager';
import * as Location from 'expo-location';

const LOCATION_TASK_NAME = 'background-location-task';

const requestPermissions = async () => {
  const { status: foregroundStatus } = await Location.requestForegroundPermissionsAsync();
  if (foregroundStatus === 'granted') {
    const { status: backgroundStatus } = await Location.requestBackgroundPermissionsAsync();
    if (backgroundStatus === 'granted') {
      await Location.startLocationUpdatesAsync(LOCATION_TASK_NAME, {
        accuracy: Location.Accuracy.Balanced,
      });
    }
  }
};

const PermissionsButton = () => (
  <View style={styles.container}>
    <Button onPress={requestPermissions} title="Enable background location" />
  </View>
);

TaskManager.defineTask(LOCATION_TASK_NAME, ({ data, error }) => {
  if (error) {
    // Error occurred - check `error.message` for more details.
    return;
  }
  if (data) {
    const { locations } = data;
    // do something with the locations captured in the background
  }
});

const styles = StyleSheet.create({
  container: {
    flex: 1,
    alignItems: 'center',
    justifyContent: 'center',
  },
});

export default PermissionsButton;

API

import * as TaskManager from 'expo-task-manager';

Methods

`TaskManager.defineTask<T>(taskName, taskExecutor)`

Parameter	Type	Description
taskName	`string`	Name of the task. It must be the same as the name you provided when registering the task.
taskExecutor	`TaskManagerTaskExecutor<T>`	A function that will be invoked when the task with given `taskName` is executed.

Defines task function. It must be called in the global scope of your JavaScript bundle. In particular, it cannot be called in any of React lifecycle methods like componentDidMount. This limitation is due to the fact that when the application is launched in the background, we need to spin up your JavaScript app, run your task and then shut down — no views are mounted in this scenario.

Returns:

void

`TaskManager.getRegisteredTasksAsync()`

Provides information about tasks registered in the app.

Returns:

Promise<TaskManagerTask[]>

A promise which fulfills with an array of tasks registered in the app. Example:

[
  {
    taskName: 'location-updates-task-name',
    taskType: 'location',
    options: {
      accuracy: Location.Accuracy.High,
      showsBackgroundLocationIndicator: false,
    },
  },
  {
    taskName: 'geofencing-task-name',
    taskType: 'geofencing',
    options: {
      regions: [...],
    },
  },
]

`TaskManager.getTaskOptionsAsync<TaskOptions>(taskName)`

Parameter	Type	Description
taskName	`string`	Name of the task.

Retrieves options associated with the task, that were passed to the function registering the task (eg. Location.startLocationUpdatesAsync).

Returns:

Promise<TaskOptions>

A promise which fulfills with the options object that was passed while registering task with given name or null if task couldn't be found.

`TaskManager.isAvailableAsync()`

Determine if the TaskManager API can be used in this app.

Returns:

Promise<boolean>

A promise fulfills with true if the API can be used, and false otherwise. On the web it always returns false.

`TaskManager.isTaskDefined(taskName)`

Parameter	Type	Description
taskName	`string`	Name of the task.

Checks whether the task is already defined.

Returns:

boolean

`TaskManager.isTaskRegisteredAsync(taskName)`

Parameter	Type	Description
taskName	`string`	Name of the task.

Determine whether the task is registered. Registered tasks are stored in a persistent storage and preserved between sessions.

Returns:

Promise<boolean>

A promise which fulfills with a boolean value whether or not the task with given name is already registered.

`TaskManager.unregisterAllTasksAsync()`

Unregisters all tasks registered for the running app. You may want to call this when the user is signing out and you no longer need to track his location or run any other background tasks.

Returns:

Promise<void>

A promise which fulfills as soon as all tasks are completely unregistered.

`TaskManager.unregisterTaskAsync(taskName)`

Parameter	Type	Description
taskName	`string`	Name of the task to unregister.

Unregisters task from the app, so the app will not be receiving updates for that task anymore. It is recommended to use methods specialized by modules that registered the task, eg. Location.stopLocationUpdatesAsync.

Returns:

Promise<void>

A promise which fulfills as soon as the task is unregistered.

Interfaces

`TaskManagerError`

Error object that can be received through TaskManagerTaskBody when the task fails.

TaskManagerError Properties

Name	Type	Description
code	`string \| number`	-
message	`string`	-

`TaskManagerTask`

Represents an already registered task.

TaskManagerTask Properties

Name	Type	Description
options	`any`	Provides `options` that the task was registered with.
taskName	`string`	Name that the task is registered with.
taskType	`string`	Type of the task which depends on how the task was registered.

`TaskManagerTaskBody`

Represents the object that is passed to the task executor.

TaskManagerTaskBody Properties

Name	Type	Description
data	`T`	An object of data passed to the task executor. Its properties depends on the type of the task.
error	`null \| TaskManagerError`	Error object if the task failed or `null` otherwise.
executionInfo	`TaskManagerTaskBodyExecutionInfo`	Additional details containing unique ID of task event and name of the task.

`TaskManagerTaskBodyExecutionInfo`

Additional details about execution provided in TaskManagerTaskBody.

TaskManagerTaskBodyExecutionInfo Properties

Name	Type	Description
appState (optional)	`'active' \| 'background' \| 'inactive'`	Only for: iOS State of the application.
eventId	`string`	Unique ID of task event.
taskName	`string`	Name of the task.

Types

`TaskManagerTaskExecutor()`

Type of task executor – a function that handles the task.

Parameter	Type
body	`TaskManagerTaskBody<T>`

Returns:

void