The documentation is currently a work in progress whilst the product is in alpha.

Foreground Service

Display a notification when running an ongoing headless task.

Foreground services are an advanced Android concept which allows you to display notifications to your users when running long lived background tasks. The notification acts like any other notification, however it cannot be removed by the user and lives for the duration of the service.

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Android Foreground Service

The service task can run for as long as required whilst the application is open, alive or killed. Once the task has complete the service is stopped and the notification is removed. Examples of when to use a Foreground Service are:

  • Capturing on-going information (such as current location for a fitness or delivery app).
  • Playing media to the user.
  • Displaying important information to the user, such as directions.
  • Showing the status of a local device task, such as deleting files.

To create a long running task, Notifee exposes a registerForegroundService method. It should be registered outside of any React components as early as possible in your code (e.g. within the project index.js file).

Creating a service

Let's create our foreground service which we'll later hook into. The callback we register must be a promise, and is passed a notification object when called.

import notifee from '@notifee/react-native';

notifee.registerForegroundService(() => {
  return new Promise(resolve => {
    // Long running task...
  });
});

Whenever the runner resolves, the foreground service will close and the notification will be removed. The service can be stopped by the device (e.g. low memory) or if the user force quits from the application settings.

Attach a notification

To attach a new notification to the service, the asForegroundService property on the notification object can be set to true:

import notifee, { AndroidColor } from '@notifee/react-native';

notifee.displayNotification({
  title: 'Foreground service',
  body: 'This notification will exist for the lifetime of the service runner',
  android: {
    channelId,
    asForegroundService: true,
    color: AndroidColor.RED,
    colorized: true,
  },
});

Running this code will create a foreground service notification which is bound to the runner we registered with registerForegroundService above. As our example never returns the promise, the notification will exist for the lifetime of the application.

You may also notice we have provided color and colorized properties. When setting colorized to true on a foreground service notification, the color will be used to change the entire background color of the notification, which is not possible on standard notifications.

Building a long lived task

To simplify the experience for developers, a long lived task will continuously run until the runner function resolves a promise. This allows us to create intervals, or subscribe to events which we can use to update the notification.

For example, we could build a task which subscribes to an event handler:

notifee.registerForegroundService(() => {
  return new Promise(resolve => {
    // Example task subscriber
    onTaskUpdate(task => {
      if (task.complete) {
        return resolve();
      }
    });
  });
});

The example code above would show the notification to the user until a new task event with complete being true is sent.

Updating an existing notification

Foreground notifications behave like any other notification, and can display anything (progress indicators, images etc). Whilst our service is running, we can also update the current notification to display different content:

notifee.registerForegroundService(notification => {
  return new Promise(resolve => {
    // Example task subscriber
    onTaskUpdate(task => {
      if (task.update) {
        notifee.displayNotification({
          id: notification.id,
          body: notification.body,
          android: {
            ...notification.android,
            progress: {
              max: task.update.total,
              current: task.update.current,
            },
          },
        });
      }

      if (task.complete) {
        return resolve();
      }
    });
  });
});

Above we've updated the callback handler for the onTaskUpdate method. Each task.update call would update the current notification with a new progress indicator position. It is important we update the existing notification by ID, otherwise the foreground service would stop and restart. Only a single foreground service notification can exist for your application at any one time.

Handling interactions

Much like other notifications, we can subscribe to events when the user interacts with the Foreground Service notification. The service task runs in it's own context, allowing us to subscribe to events within itself.

For example, to stop the foreground service when a user presses an action, we can subscribe to the event inside of the task:

import notifee, { EventType } from '@notifee/react-native';

// Create the task runner
notifee.registerForegroundService(notification => {
  return new Promise(resolve => {
    notifee.onForegroundEvent(({ type, detail }) => {
      if (type === EventType.ACTION_PRESS && detail.pressAction.id === 'stop') {
        return resolve();
      }
    });
  });
});

A notification can then be created with a Quick Action which triggers the event:

notifee.displayNotification({
  title: 'Foreground Service Notification',
  body: 'Press the Quick Action to stop the service',
  android: {
    channelId,
    actions: [
      {
        title: 'Stop',
        pressAction: {
          id: 'stop',
        },
      },
    ],
  },
});

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