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transistorsoft / cordova-plugin-background-fetch

Implements background fetching of data.
MIT License
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cordova-plugin-background-fetch · [npm]() [npm]()

By Transistor Software, creators of Cordova Background Geolocation

:new: :stop_sign: Capacitor version now available! See capacitor-background-fetch :stop_sign:

Background Fetch is a very simple plugin which attempts to awaken an app in the background about every 15 minutes, providing a short period of background running-time. This plugin will execute your provided callbackFn whenever a background-fetch event occurs.

There is no way to increase the rate which a fetch-event occurs and this plugin sets the rate to the most frequent possible — you will never receive an event faster than 15 minutes. The operating-system will automatically throttle the rate the background-fetch events occur based upon usage patterns. Eg: if user hasn't turned on their phone for a long period of time, fetch events will occur less frequently or if an iOS user disables background refresh they may not happen at all.

:new: Background Fetch now provides a scheduleTask method for scheduling arbitrary "one-shot" or periodic tasks.

iOS

Android

Contents

Using the plugin


## Installing the plugin ##

#### :warning: *Cocoapods* >= `1.10.0` is required:
```console
$ pod --version
// if < 1.10.0
$ sudo gem install cocoapods
cordova plugin add cordova-plugin-background-fetch

Setup

iOS Setup

If you intend to execute your own custom tasks via BackgroundFetch.scheduleTask, for example:

BackgroundFetch.scheduleTask({
  taskId: 'com.transistorsoft.customtask1',  // <-- Your custom task-identifier
  delay: 60 * 60 * 1000  //  In one hour (milliseconds)
});
.
.
.
BackgroundFetch.scheduleTask({
  taskId: 'com.transistorsoft.customtask2',  // <-- Your custom task-identifier
  delay: 60 * 60 * 1000  //  In one hour (milliseconds)
});

You must register these custom task-identifiers with your iOS app's Info.plist "Permitted background task scheduler identifiers":

:open_file_folder: In your config.xml, find the <platform name="ios"> container and register your custom task-identifier(s):

  <platform name="ios">
      <config-file parent="BGTaskSchedulerPermittedIdentifiers" target="*-Info.plist">
          <array>
              <string>com.transistorsoft.customtask1</string>
              <string>com.transistorsoft.customtask2</string>
          </array>
      </config-file>
  </platform>

:warning: A task identifier can be any string you wish, but it's a good idea to prefix them now with com.transistorsoft. — In the future, the com.transistorsoft prefix may become required.

Privacy Manifest

Apple now requires apps provide a Privacy Manifest for "sensitive" APIs which could be abused for "fingerprinting" a user for malicious marketing activity.

:warning: You MUST upgrade your cordova-ios platform to >= 7.1.0 for iOS Privacy Manifest Support:

  <platform name="ios">
      <privacy-manifest>
          <key>NSPrivacyAccessedAPITypes</key>
          <array>
              <!-- [1] background-fetch: UserDefaults -->
              <dict>
                  <key>NSPrivacyAccessedAPIType</key>
                  <string>NSPrivacyAccessedAPICategoryUserDefaults</string>

                  <key>NSPrivacyAccessedAPITypeReasons</key>
                  <array>
                      <string>CA92.1</string>
                  </array>
              </dict>
              <!-- [1] background-fetch -->
          </array>
      </privacy-manifest>
  </platform>

Android Setup (optional)

Only If you wish to use precise scheduling of events with forceAlarmManager: true, Android 14 (SDK 34), has restricted usage of "AlarmManager exact alarms". To continue using precise timing of events with Android 14, you can manually add this permission to your AndroidManifest. Otherwise, the plugin will gracefully fall-back to "in-exact AlarmManager scheduling":

:open_file_folder: In your config.xml, add the following block within the <platform name="android"> block (exactly as-shown:

  <platform name="android">
      <config-file parent="/manifest" target="app/src/main/AndroidManifest.xml">
          <uses-permission android:minSdkVersion="34" android:name="android.permission.USE_EXACT_ALARM" />
      </config-file>
  </platform>

:warning: It has been announced that Google Play Store has plans to impose greater scrutiny over usage of this permission (which is why the plugin does not automatically add it).

Example

Pure Cordova Javascript (eg: Ionic 1)

onDeviceReady: async function() {
  var BackgroundFetch = window.BackgroundFetch;

  // Your BackgroundFetch event handler.
  var onEvent = async function(taskId) {
      console.log('[BackgroundFetch] event received: ', taskId);
      // Required: Signal completion of your task to native code
      // If you fail to do this, the OS can terminate your app
      // or assign battery-blame for consuming too much background-time
      BackgroundFetch.finish(taskId);
  };

  // Timeout callback is executed when your Task has exceeded its allowed running-time.
  // You must stop what you're doing immediately BackgroundFetch.finish(taskId)
  var onTimeout = async function(taskId) {
      console.log('[BackgroundFetch] TIMEOUT: ', taskId);
      BackgroundFetch.finish(taskId);
  };

  var status = await BackgroundFetch.configure({minimumFetchInterval: 15}, onEvent, onTimeout);
  console.log('[BackgroundFetch] configure status: ', status);
}

Ionic 2+ Example

import { Component } from '@angular/core';
import { NavController, Platform } from 'ionic-angular';

import BackgroundFetch from "cordova-plugin-background-fetch";

@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {
  constructor(public navCtrl: NavController, public platform: Platform) {
    this.platform.ready().then(this.onDeviceReady.bind(this));
  }

  async onDeviceReady() {
    // Your BackgroundFetch event handler.
    let onEvent = async (taskId) => {
        console.log('[BackgroundFetch] event received: ', taskId);
        // Required: Signal completion of your task to native code
        // If you fail to do this, the OS can terminate your app
        // or assign battery-blame for consuming too much background-time
        BackgroundFetch.finish(taskId);
    };

    // Timeout callback is executed when your Task has exceeded its allowed running-time.
    // You must stop what you're doing immediately BackgroundFetch.finish(taskId)
    let onTimeout = async (taskId) => {
        console.log('[BackgroundFetch] TIMEOUT: ', taskId);
        BackgroundFetch.finish(taskId);
    };

    // Configure the plugin.
    let status = await BackgroundFetch.configure({minimumFetchInterval: 15}, onEvent, onTimeout);
    console.log('[BackgroundFetch] configure, status: ', status);
  }
}

Executing Custom Tasks

In addition to the default background-fetch task defined by BackgroundFetch.configure, you may also execute your own arbitrary "oneshot" or periodic tasks (iOS requires additional Setup Instructions). However, all events will be fired into the Callback provided to BackgroundFetch#configure:

⚠️ iOS:

// Step 1:  Configure BackgroundFetch as usual.
let status = await BackgroundFetch.configure({
  minimumFetchInterval: 15
}, (taskId) => {  // <-- Event callback.
  console.log("[BackgroundFetch] taskId: ", taskId);

  // Use a switch statement to route task-handling.
  switch (taskId) {
    case 'com.transistorsoft.customtask':
      print("Received custom task");
      break;
    default:
      print("Default fetch task");
  }
  // Finish, providing received taskId.
  BackgroundFetch.finish(taskId);
}, (taskId) => {  // <-- Task timeout callback.
  // This task has exceeded its allowed running-time.
  // You must stop what you're doing and immediately .finish(taskId)
  console.log('[BackgroundFetch] TIMEOUT taskId: ', taskId);
  BackgroundFetch.finish(taskId);
});

// Step 2:  Schedule a custom "oneshot" task "com.transistorsoft.customtask" to execute 5000ms from now.
BackgroundFetch.scheduleTask({
  taskId: "com.transistorsoft.customtask",
  forceAlarmManager: true,
  delay: 5000  // <-- milliseconds
});

API Documentation

Config

Common Options

@param {Integer} minimumFetchInterval [15]

The minimum interval in minutes to execute background fetch events. Defaults to 15 minutes. Note: Background-fetch events will never occur at a frequency higher than every 15 minutes. Apple uses a secret algorithm to adjust the frequency of fetch events, presumably based upon usage patterns of the app. Fetch events can occur less often than your configured minimumFetchInterval.

@param {Integer} delay (milliseconds)

:information_source: Valid only for BackgroundGeolocation.scheduleTask. The minimum number of milliseconds in future that task should execute.

@param {Boolean} periodic [false]

:information_source: Valid only for BackgroundGeolocation.scheduleTask. Defaults to false. Set true to execute the task repeatedly. When false, the task will execute just once.

Android Options

@config {Boolean} stopOnTerminate [true]

Set false to continue background-fetch events after user terminates the app. Default to true.

@config {Boolean} startOnBoot [false]

Set true to initiate background-fetch events when the device is rebooted. Defaults to false.

:exclamation: NOTE: startOnBoot requires stopOnTerminate: false.

@config {Boolean} forceAlarmManager [false]

By default, the plugin will use Android's JobScheduler when possible. The JobScheduler API prioritizes for battery-life, throttling task-execution based upon device usage and battery level.

Configuring forceAlarmManager: true will bypass JobScheduler to use Android's older AlarmManager API, resulting in more accurate task-execution at the cost of higher battery usage.

let status = await BackgroundFetch.configure({
  minimumFetchInterval: 15,
  forceAlarmManager: true
}, async (taskId) => {
  console.log("[BackgroundFetch] taskId: ", taskId);
  BackgroundFetch.finish(taskId);
}, async (taskId) => {
  // This task has exceeded its allowed running-time.
  // You must stop what you're doing and immediately .finish(taskId)
  console.log('[BackgroundFetch] TIMEOUT taskId: ', taskId);
  BackgroundFetch.finish(taskId);
});
.
.
.
// And with with #scheduleTask
BackgroundFetch.scheduleTask({
  taskId: 'com.transistorsoft.customtask',
  delay: 5000,       // milliseconds
  forceAlarmManager: true
  periodic: false
});

@config {integer} requiredNetworkType [BackgroundFetch.NETWORK_TYPE_NONE]

Set basic description of the kind of network your job requires.

If your job doesn't need a network connection, you don't need to use this option as the default value is BackgroundFetch.NETWORK_TYPE_NONE.

NetworkType Description
BackgroundFetch.NETWORK_TYPE_NONE This job doesn't care about network constraints, either any or none.
BackgroundFetch.NETWORK_TYPE_ANY This job requires network connectivity.
BackgroundFetch.NETWORK_TYPE_CELLULAR This job requires network connectivity that is a cellular network.
BackgroundFetch.NETWORK_TYPE_UNMETERED This job requires network connectivity that is unmetered.
BackgroundFetch.NETWORK_TYPE_NOT_ROAMING This job requires network connectivity that is not roaming.

@config {Boolean} requiresBatteryNotLow [false]

Specify that to run this job, the device's battery level must not be low.

This defaults to false. If true, the job will only run when the battery level is not low, which is generally the point where the user is given a "low battery" warning.

@config {Boolean} requiresStorageNotLow [false]

Specify that to run this job, the device's available storage must not be low.

This defaults to false. If true, the job will only run when the device is not in a low storage state, which is generally the point where the user is given a "low storage" warning.

@config {Boolean} requiresCharging [false]

Specify that to run this job, the device must be charging (or be a non-battery-powered device connected to permanent power, such as Android TV devices). This defaults to false.

@config {Boolean} requiresDeviceIdle [false]

When set true, ensure that this job will not run if the device is in active use.

The default state is false: that is, the for the job to be runnable even when someone is interacting with the device.

This state is a loose definition provided by the system. In general, it means that the device is not currently being used interactively, and has not been in use for some time. As such, it is a good time to perform resource heavy jobs. Bear in mind that battery usage will still be attributed to your application, and surfaced to the user in battery stats.

@config {Boolean} enableHeadless [false]

:warning: For advanced users only. In order to use enableHeadless: true, you must be prepared to write Java code. If you're not prepared to write Java code, turn away now and do not enable this :warning:.

When your application is terminated with stopOnTerminate: false, your Javascript app (and your Javascript fetch callback) are terminated. However, the plugin provides a mechanism for you to handle background-fetch events in the Native Android Environment.

Some examples where you could use the "Headless" mechanism:

Headless Fetch Setup

  1. create a new file in your Cordova application named BackgroundFetchHeadlessTask.java. :warning: The file can be located anywhere in your app but MUST be named BackgroundFetchHeadlessTask.java.

eg: :open_file_folder: src/android/BackgroundFetchHeadlessTask.java

package com.transistorsoft.cordova.backgroundfetch;
import android.content.Context;
import com.transistorsoft.tsbackgroundfetch.BackgroundFetch;
import com.transistorsoft.tsbackgroundfetch.BGTask;
import android.util.Log;

public class BackgroundFetchHeadlessTask implements HeadlessTask {
    @Override
    public void onFetch(Context context, BGTask task) {
        String taskId = task.getTaskId();
        boolean isTimeout = task.getTimedOut();
        if (isTimeout) {
          Log.d(BackgroundFetch.TAG, "My BackgroundFetchHeadlessTask TIMEOUT: " + taskId);
          BackgroundFetch.getInstance(context).finish(taskId);
          return;
        }
        Log.d(BackgroundFetch.TAG, "My BackgroundFetchHeadlessTask:  onFetch: " + taskId);
        // Perform your work here....

        // Just as in Javascript callback, you must signal #finish
        BackgroundFetch.getInstance(context).finish(taskId);
    }
}
  1. In your config.xml, add the following <resource-file> element to the <platform name="android">: 
    <platform name="android">
<resource-file src="https://github.com/transistorsoft/cordova-plugin-background-fetch/raw/master/src/android/BackgroundFetchHeadlessTask.java" target="app/src/main/java/com/transistorsoft/cordova/backgroundfetch/BackgroundFetchHeadlessTask.java" />
</platform>
    • src: path to your custom BackgroundFetchHeadlessTask.java file.
    • target: :warning: Must be exactly as shown above.

This will copy your custom Java source-file into the cordova-plugin-background-fetch plugin, effectively overriding the plugin.

:warning: You're responsible for managing your own gradle dependencies. To import 3rd-party libraries, you'll have to import your own custom build-extras.gradle (See "build-extras" here in the Cordova Android Platform Documentation)

Methods

Method Name Arguments Returns Notes
configure {BackgroundFetchConfig}, callbackFn, timeoutFn Promise<BackgroundFetchStatus> Configures the plugin's fetch callbackFn and timeoutFn. This callbackFn will fire each time an iOS background-fetch event occurs (typically every 15 min). The timeoutFn will be called when the OS reports your task is nearing the end of its allowed background-time.
scheduleTask {TaskConfig} Void Executes a custom task. The task will be executed in the same Callback function provided to #configure.
stopTask String taskId, successFn,failureFn Void Stops a scheduleTask from running.
finish String taskId Void You MUST call this method in your callbackFn provided to #configure in order to signal to the OS that your task is complete. iOS provides only 30s of background-time for a fetch-event -- if you exceed this 30s, iOS will kill your app.
start successFn, failureFn Void Start the background-fetch API. Your callbackFn provided to #configure will be executed each time a background-fetch event occurs. NOTE the #configure method automatically calls #start. You do not have to call this method after you #configure the plugin
stop successFn, failureFn Void Stop the background-fetch API from firing fetch events. Your callbackFn provided to #configure will no longer be executed.
status callbackFn Void Your callback will be executed with the current status (Integer) 0: Restricted, 1: Denied, 2: Available. These constants are defined as BackgroundFetch.STATUS_RESTRICTED, BackgroundFetch.STATUS_DENIED, BackgroundFetch.STATUS_AVAILABLE (NOTE: Android will always return STATUS_AVAILABLE)

Debugging

iOS

:new: BGTaskScheduler API for iOS 13+

Simulating task-timeout events

First comment-out your call to BackgroundFetch.finish(taskId) in your eventCallback to simulate a task taking too long.

let status = await BackgroundFetch.configure({
  minimumFetchInterval: 15
}, async (taskId) => {  // <-- Event callback.
  // This is the task callback.
  console.log("[BackgroundFetch] taskId", taskId);
  ////
  // NOTE:  Disable BackgroundFetch.finish(taskId) when simulating an iOS task timeout
  //BackgroundFetch.finish(taskId);
  //
}, async (taskId) => {  // <-- Event timeout callback
  // This task has exceeded its allowed running-time.
  // You must stop what you're doing and immediately .finish(taskId)
  print("[BackgroundFetch] TIMEOUT taskId:", taskId);
  BackgroundFetch.finish(taskId);
});

Old BackgroundFetch API

Android



## Licence ##

The MIT License

Copyright (c) 2018 Chris Scott, Transistor Software <chris@transistorsoft.com>
http://transistorsoft.com

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.