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react-native-background-downloader banner

npm version

@kesha-antonov/react-native-background-downloader

*Note - This is fork of https://github.com/EkoLabs/react-native-background-downloader maintained by https://github.com/kesha-antonov *

A library for React-Native to help you download large files on iOS and Android both in the foreground and most importantly in the background.

Why?

On iOS, if you want to download big files no matter the state of your app, wether it's in the background or terminated by the OS, you have to use a system API called NSURLSession.

This API handles your downloads separately from your app and only keeps it informed using delegates (Read: Downloading Files in the Background).

On Android we are simulating this process with a wonderful library called Fetch2

The real challenge of using this method is making sure the app's UI is always up-to-date with the downloads that are happening in another process because your app might startup from scratch while the downloads are still running.

@kesha-antonov/react-native-background-downloader gives you an easy API to both downloading large files and re-attaching to those downloads once your app launches again.

Please Note - This library was created to better facilitate background downloading on iOS. If you're not aiming to to use the download-in-background functionality, there are better solutions like RNFS.downloadFile() which will results in a more stable download experience for your app.

ToC

Getting started

yarn add @kesha-antonov/react-native-background-downloader

or

npm i @kesha-antonov/react-native-background-downloader

Then:

cd ios && pod install

Mostly automatic installation

Any React Native version >= 0.60 supports autolinking so nothing should be done.

For anything < 0.60 run the following link command

$ react-native link @kesha-antonov/react-native-background-downloader

Manual installation

iOS

  1. In XCode, in the project navigator, right click Libraries ➜ Add Files to [your project's name]
  2. Go to node_modules ➜ @kesha-antonov/react-native-background-downloader and add RNBackgroundDownloader.xcodeproj
  3. In XCode, in the project navigator, select your project. Add libRNBackgroundDownloader.a to your project's Build Phases ➜ Link Binary With Libraries
  4. Run your project (Cmd+R)

Android

  1. Open up android/app/src/main/java/[...]/MainActivity.java
  • Add import com.eko.RNBackgroundDownloaderPackage; to the imports at the top of the file
  • Add new RNBackgroundDownloaderPackage() to the list returned by the getPackages() method
  1. Append the following lines to android/settings.gradle: 
    include ':react-native-background-downloader'
project(':react-native-background-downloader').projectDir = new File(rootProject.projectDir, 	'../node_modules/@kesha-antonov/react-native-background-downloader/android')
  2. Insert the following lines inside the dependencies block in android/app/build.gradle: 
      compile project(':react-native-background-downloader')

iOS - Extra Mandatory Step

In your AppDelegate.m add the following code:

...
#import <RNBackgroundDownloader.h>

...

- (void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier completionHandler:(void (^)(void))completionHandler
{
  [RNBackgroundDownloader setCompletionHandlerWithIdentifier:identifier completionHandler:completionHandler];
}

...

Failing to add this code will result in canceled background downloads. If Xcode complains that RNBackgroundDownloader.h is missing, you might have forgotten to pod install first.

Usage

Downloading a file

import { Platform } from 'react-native'
import { download, completeHandler } from '@kesha-antonov/react-native-background-downloader'

const jobId = 'file123'

let task = download({
	id: jobId,
	url: 'https://link-to-very.large/file.zip',
	destination: `${RNBackgroundDownloader.directories.documents}/file.zip`,
	metadata: {}
}).begin(({ expectedBytes, headers }) => {
	console.log(`Going to download ${expectedBytes} bytes!`)
}).progress(percent => {
	console.log(`Downloaded: ${percent * 100}%`)
}).done(() => {
	console.log('Download is done!')

  // PROCESS YOUR STUFF

  // FINISH DOWNLOAD JOB ON IOS
  if (Platform.OS === 'ios')
    completeHandler(jobId)
}).error(error => {
	console.log('Download canceled due to error: ', error);
})

// Pause the task
task.pause()

// Resume after pause
task.resume()

// Cancel the task
task.stop()

Re-Attaching to background downloads

This is the main selling point of this library (but it's free!).

What happens to your downloads after the OS stopped your app? Well, they are still running, we just need to re-attach to them.

Add this code to app's init stage, and you'll never lose a download again!

import RNBackgroundDownloader from '@kesha-antonov/react-native-background-downloader'

let lostTasks = await RNBackgroundDownloader.checkForExistingDownloads()
for (let task of lostTasks) {
	console.log(`Task ${task.id} was found!`)
	task.progress(percent => {
		console.log(`Downloaded: ${percent * 100}%`)
	}).done(() => {
		console.log('Download is done!')
	}).error(error => {
		console.log('Download canceled due to error: ', error)
	})
}

task.id is very important for re-attaching the download task with any UI component representing that task. This is why you need to make sure to give sensible IDs that you know what to do with, try to avoid using random IDs.

Using custom headers

If you need to send custom headers with your download request, you can do in it 2 ways:

  1. Globally using RNBackgroundDownloader.setHeaders():
RNBackgroundDownloader.setHeaders({
    Authorization: 'Bearer 2we$@$@Ddd223'
})

This way, all downloads with have the given headers.

  1. Per download by passing a headers object in the options of RNBackgroundDownloader.download():
let task = RNBackgroundDownloader.download({
	id: 'file123',
	url: 'https://link-to-very.large/file.zip'
	destination: `${RNBackgroundDownloader.directories.documents}/file.zip`,
	headers: {
	    Authorization: 'Bearer 2we$@$@Ddd223'
	}
}).begin(({ expectedBytes, headers }) => {
	console.log(`Going to download ${expectedBytes} bytes!`)
}).progress(percent => {
	console.log(`Downloaded: ${percent * 100}%`)
}).done(() => {
	console.log('Download is done!')
}).error(error => {
	console.log('Download canceled due to error: ', error)
})

Headers given in the download function are merged with the ones given in setHeaders.

API

RNBackgroundDownloader

download(options)

Download a file to destination

options

An object containing options properties

Property Type Required Platforms Info
id String ✅ All A Unique ID to provide for this download. This ID will help to identify the download task when the app re-launches
url String ✅ All URL to file you want to download
destination String ✅ All Where to copy the file to once the download is done
metadata Object All Data to be preserved on reboot.
headers Object All Costume headers to add to the download request. These are merged with the headers given in the setHeaders function
priority Priority (enum) Android The priority of the download. On Android, downloading is limited to 4 simultaneous instances where further downloads are queued. Priority helps in deciding which download to pick next from the queue. Default: Priority.MEDIUM
network Network (enum) Android Give your the ability to limit the download to WIFI only. Default: Network.ALL

returns

DownloadTask - The download task to control and monitor this download

checkForExistingDownloads()

Checks for downloads that ran in background while you app was terminated. And also forces them to resume downloads.

Recommended to run at the init stage of the app.

returns

DownloadTask[] - Array of tasks that were running in the background so you can re-attach callbacks to them

setHeaders(headers)

Sets headers to use in all future downloads.

headers - Object

DownloadTask

A class representing a download task created by RNBackgroundDownloader.download

Members

Name Type Info
id String The id you gave the task when calling RNBackgroundDownloader.download
metadata Object The metadata you gave the task when calling RNBackgroundDownloader.download
percent Number The current percent of completion of the task between 0 and 1
bytesWritten Number The number of bytes currently written by the task
totalBytes Number The number bytes expected to be written by this task or more plainly, the file size being downloaded

completeHandler(jobId)

Finishes download job on iOS and informs OS that app can be closed in background if needed. After finishing download in background you have some time to process your JS logic and finish the job.

ensureDownloadsAreRunning

Pauses and resumes all downloads - this is fix for stuck downloads. Use it when your app loaded and is ready for handling downloads (all your logic loaded and ready to handle download callbacks).

Here's example of how you can use it:

  1. When your app just loaded

Either stop all tasks:

const tasks = await checkForExistingDownloads()
for (const task of tasks)
	task.stop()

Or re-attach them:

const tasks = await checkForExistingDownloads()
for (const task of tasks) {
	task.pause()
	//
	// YOUR LOGIC OF RE-ATTACHING DOWLOADS TO YOUR STUFF
	// ...
	//
}

  1. Prepare your app to handle downloads... (load your state etc.)

  2. Add listener to handle when your app goes foreground (be sure to do it only after you stopped all tasks or re-attached them!)

function handleAppStateChange (appState) {
	if (appState !== 'active')
		return

	ensureDownloadsAreRunning()
}

const appStateChangeListener = AppState.addEventListener('change', handleAppStateChange)
  1. Call ensureDownloadsAreRunning() after all was setup.

Callback Methods

Use these methods to stay updated on what's happening with the task.

All callback methods return the current instance of the DownloadTask for chaining.

Function Callback Arguments Info
begin { expectedBytes, headers } Called when the first byte is received. 💡: this is good place to check if the device has enough storage space for this download
progress percent, bytesWritten, totalBytes Called at max every 1.5s so you can update your progress bar accordingly
done Called when the download is done, the file is at the destination you've set
error error Called when the download stops due to an error

pause()

Pauses the download

resume()

Resumes a pause download

stop()

Stops the download for good and removes the file that was written so far

Constants

directories

documents

An absolute path to the app's documents directory. It is recommended that you use this path as the target of downloaded files.

Priority (enum) - Android only

Priority.HIGH

Priority.MEDIUM - Default ✅

Priority.LOW

Network (enum) - Android only

Network.WIFI_ONLY

Network.ALL - Default ✅

Authors

Developed by Elad Gil of Eko

Maintained by Kesha Antonov

License

Apache 2