---
title: Downloading media
---

ExoPlayer provides functionality to download media for offline playback. In most
use cases it's desirable for downloads to continue even when your app is in the
background. For these use cases your app should subclass `DownloadService`, and
send commands to the service to add, remove and control the downloads. The
diagram below shows the main classes that are involved.

{% include figure.html url="/images/downloading.svg" index="1" caption="Classes
for downloading media. The arrow directions indicate the flow of data."
width="85%" %}

* `DownloadService`: Wraps a `DownloadManager` and forwards commands to it. The
  service allows the `DownloadManager` to keep running even when the app is in
  the background.
* `DownloadManager`: Manages multiple downloads, loading (and storing) their
  states from (and to) a `DownloadIndex`, starting and stopping downloads based
  on requirements such as network connectivity, and so on. To download the
  content, the manager will typically read the data being downloaded from a
  `HttpDataSource`, and write it into a `Cache`.
* `DownloadIndex`: Persists the states of the downloads.

## Creating a DownloadService ##

To create a `DownloadService`, you need to subclass it and implement its
abstract methods:

* `getDownloadManager()`: Returns the `DownloadManager` to be used.
* `getScheduler()`: Returns an optional `Scheduler`, which can restart the
  service when requirements needed for pending downloads to progress are met.
  ExoPlayer provides these implementations:
  * `PlatformScheduler`, which uses [JobScheduler][] (Minimum API is 21). See
    the [PlatformScheduler][] javadocs for app permission requirements.
  * `WorkManagerScheduler`, which uses [WorkManager][].
  * `JobDispatcherScheduler`, which uses [Firebase JobDispatcher][]
  (Deprecated). See the [JobDispatcherScheduler][] javadocs for app permission
  requirements.
* `getForegroundNotification()`: Returns a notification to be displayed when the
  service is running in the foreground. You can use
  `DownloadNotificationHelper.buildProgressNotification` to create a
  notification in default style.

Finally, you need to define the service in your `AndroidManifest.xml` file:

~~~
<service android:name="com.myapp.MyDownloadService"
    android:exported="false">
  <!-- This is needed for Scheduler -->
  <intent-filter>
    <action android:name="com.google.android.exoplayer.downloadService.action.RESTART"/>
    <category android:name="android.intent.category.DEFAULT"/>
  </intent-filter>
</service>
~~~
{: .language-xml}

See [`DemoDownloadService`][] and [`AndroidManifest.xml`][] in the ExoPlayer
demo app for a concrete example.

## Creating a DownloadManager ##

The following code snippet demonstrates how to instantiate a `DownloadManager`,
which can be returned by `getDownloadManager()` in your `DownloadService`:

~~~
// Note: This should be a singleton in your app.
databaseProvider = new ExoDatabaseProvider(context);

// A download cache should not evict media, so should use a NoopCacheEvictor.
downloadCache = new SimpleCache(
    downloadDirectory,
    new NoOpCacheEvictor(),
    databaseProvider);

// Create a factory for reading the data from the network.
dataSourceFactory = new DefaultHttpDataSourceFactory(userAgent);

// Create the download manager.
downloadManager = new DownloadManager(
    context,
    databaseProvider,
    downloadCache,
    dataSourceFactory);

// Optionally, setters can be called to configure the download manager.
downloadManager.setRequirements(requirements);
downloadManager.setMaxParallelDownloads(3);
~~~
{: .language-java}

See [`DemoApplication`][] in the demo app for a concrete example.

The example in the demo app also imports download state from legacy `ActionFile`
instances. This is only necessary if your app used `ActionFile` prior to
ExoPlayer 2.10.0.
{:.info}

## Adding a download ##

To add a download you need to create a `DownloadRequest` and send it to your
`DownloadService`. For adaptive streams `DownloadHelper` can be used to help
build a `DownloadRequest`, as described [further down this page][]. The example
below shows how to create a download request for a progressive stream:

~~~
DownloadRequest downloadRequest = new DownloadRequest(
    contentId,
    DownloadRequest.TYPE_PROGRESSIVE,
    contentUri,
    /* streamKeys= */ Collections.emptyList(),
    /* customCacheKey= */ null,
    appData);
~~~
{: .language-java}

where `contentId` is a unique identifier for the content, and `appData` is any
data that the app wishes to associate with the download. In simple cases, the
`contentUri` can often be used as the `contentId`, however apps are free to use
whatever ID scheme best suits their use case.

Once created, the request can be sent to the `DownloadService` to add the
download:

~~~
DownloadService.sendAddDownload(
    context,
    MyDownloadService.class,
    downloadRequest,
    /* foreground= */ false)
~~~
{: .language-java}

where `MyDownloadService` is the app's `DownloadService` subclass, and the
`foreground` parameter controls whether the service will be started in the
foreground. If your app is already in the foreground then the `foreground`
parameter should normally be set to `false`, since the `DownloadService` will
put itself in the foreground if it determines that it has work to do.

## Removing downloads ##

A download can be removed by sending a remove command to the `DownloadService`,
where `contentId` identifies the download to be removed:

~~~
DownloadService.sendRemoveDownload(
    context,
    MyDownloadService.class,
    contentId,
    /* foreground= */ false)
~~~
{: .language-java}

You can also remove all downloaded data with
`DownloadService.sendRemoveAllDownloads`.

## Starting and stopping downloads ##

A download will only progress if four conditions are met:

* The download doesn't have a stop reason (see below).
* Downloads aren't paused.
* The requirements for downloads to progress are met. Requirements can specify
  constraints on the allowed network types, as well as whether the device should
  be idle or connected to a charger.
* The maximum number of parallel downloads is not exceeded.

All of these conditions can be controlled by sending commands to your
`DownloadService`.

#### Setting and clearing download stop reasons ####

It's possible to set a reason for one or all downloads being stopped:

~~~
// Set the stop reason for a single download.
DownloadService.sendSetStopReason(
    context,
    MyDownloadService.class,
    contentId,
    stopReason,
    /* foreground= */ false);

// Clear the stop reason for a single download.
DownloadService.sendSetStopReason(
    context,
    MyDownloadService.class,
    contentId,
    Download.STOP_REASON_NONE,
    /* foreground= */ false);
~~~
{: .language-java}

where `stopReason` can be any non-zero value (`Download.STOP_REASON_NONE = 0` is
a special value meaning that the download is not stopped). Apps that have
multiple reasons for stopping downloads can use different values to keep track
of why each download is stopped. Setting and clearing the stop reason for all
downloads works the same way as setting and clearing the stop reason for a
single download, except that `contentId` should be set to `null`.

When a download has a non-zero stop reason, it will be in the
`Download.STATE_STOPPED` state.

#### Pausing and resuming all downloads ####

All downloads can be paused and resumed as follows:

~~~
// Pause all downloads.
DownloadService.sendPauseDownloads(
    context,
    MyDownloadService.class,
    /* foreground= */ false);

// Resume all downloads.
DownloadService.sendResumeDownloads(
    context,
    MyDownloadService.class,
    /* foreground= */ false);
~~~
{: .language-java}

When a download is paused, it will be in the `Download.STATE_QUEUED` state.

#### Setting the requirements for downloads to progress ####

[`Requirements`][] can be used to specify constraints that must be met for
downloads to proceed. The requirements can be set by calling
`DownloadManager.setRequirements()` when creating the `DownloadManager`, as in
the example [above][]. They can also be changed dynamically by sending a command
to the `DownloadService`:

~~~
// Set the download requirements.
DownloadService.sendSetRequirements(
    context,
    MyDownloadService.class,
    requirements,
    /* foreground= */ false);
~~~
{: .language-java}

When a download cannot proceed because the requirements are not met, it
will be in the `Download.STATE_QUEUED` state. You can query the not met
requirements with `DownloadManager.getNotMetRequirements()`.

#### Setting the maximum number of parallel downloads ####

The maximum number of parallel downloads can be set by calling
`DownloadManager.setMaxParallelDownloads()`. This would normally be done when
creating the `DownloadManager`, as in the example [above][].

When a download cannot proceed because the maximum number of parallel downloads
are already in progress, it will be in the `Download.STATE_QUEUED` state.

## Querying downloads ##

The `DownloadIndex` of a `DownloadManager` can be queried for the state of all
downloads, including those that have completed or failed. The `DownloadIndex`
can be obtained by calling `DownloadManager.getDownloadIndex()`. A cursor that
iterates over all downloads can then be obtained by calling
`DownloadIndex.getDownloads()`. Alternatively, the state of a single download
can be queried by calling `DownloadIndex.getDownload()`.

`DownloadManager` also provides `DownloadManager.getCurrentDownloads()`, which
returns the state of current (i.e. not completed or failed) downloads only. This
method is useful for updating notifications and other UI components that display
the progress and status of current downloads.

## Listening to downloads ##

You can add a listener to `DownloadManager` to be informed when current
downloads change state:

~~~
downloadManager.addListener(
    new DownloadManager.Listener() {
      // Override methods of interest here.
    });
~~~
{: .language-java}

See `DownloadManagerListener` in the demo app's [`DownloadTracker`][] class for
a concrete example.

Download progress updates do not trigger calls on `DownloadManager.Listener`. To
update a UI component that shows download progress, you should periodically
query the `DownloadManager` at your desired update rate. [`DownloadService`][]
contains an example of this, which periodically updates the service foreground
notification.
{:.info}

## Playing downloaded content ##

Playing downloaded content is similar to playing online content, except that
data is read from the download `Cache` instead of over the network.

It's important that you do not try and read files directly from the download
directory. Instead, use ExoPlayer library classes as described below.
{:.info}

To play downloaded content, create a `CacheDataSourceFactory` using the same
`Cache` instance that was used for downloading. Using this factory, construct
a `MediaSource` for playback. You should build the `MediaSource` using the
original `contentUri` (i.e. the one from which the content was downloaded), not
a URI that points to the download directory or any file within it.

~~~
CacheDataSourceFactory dataSourceFactory = new CacheDataSourceFactory(
    downloadCache, upstreamDataSourceFactory);
ProgressiveMediaSource mediaSource = new ProgressiveMediaSource
    .Factory(dataSourceFactory)
    .createMediaSource(contentUri);
player.prepare(mediaSource);
~~~
{: .language-java}

## Downloading and playing adaptive streams ##

Adaptive streams (e.g. DASH, SmoothStreaming and HLS) normally contain multiple
media tracks. There are often multiple tracks that contain the same content in
different qualities (e.g. SD, HD and 4K video tracks). There may also be
multiple tracks of the same type containing different content (e.g. multiple
audio tracks in different languages).

For streaming playbacks, a track selector can be used to choose which of the
tracks are played. Similarly, for downloading, a `DownloadHelper` can be used to
choose which of the tracks are downloaded. Typical usage of a `DownloadHelper`
follows these steps:

1. Build a `DownloadHelper` using one of the `DownloadHelper.forXXX` methods.
1. Prepare the helper using `prepare(DownloadHelper.Callback)` and wait for the
   callback.
   ~~~
   DownloadHelper downloadHelper =
       DownloadHelper.forDash(
           context,
           contentUri,
           dataSourceFactory,
           new DefaultRenderersFactory(context));
   downloadHelper.prepare(myCallback);
   ~~~
   {: .language-java}
1. Optionally, inspect the default selected tracks using `getMappedTrackInfo`
   and `getTrackSelections`, and make adjustments using `clearTrackSelections`,
   `replaceTrackSelections` and `addTrackSelection`.
1. Create a `DownloadRequest` for the selected tracks by calling
   `getDownloadRequest`. The request can be passed to your `DownloadService` to
   add the download, as described above.
1. Release the helper using `release()`.

You can create a `MediaSource` for playback by calling
`DownloadHelper.createMediaSource`:

~~~
MediaSource mediaSource =
    DownloadHelper.createMediaSource(downloadRequest, dataSourceFactory);
~~~
{: .language-java}

The created `MediaSource` is aware of which tracks have been downloaded, and so
will only attempt to use these tracks during playback. See [`PlayerActivity`][]
in the demo app for a concrete example.

[JobScheduler]: {{ site.android_sdk }}/android/app/job/JobScheduler
[PlatformScheduler]: {{ site.exo_sdk }}/scheduler/PlatformScheduler.html
[JobDispatcherScheduler]: {{ site.exo_sdk }}/ext/jobdispatcher/JobDispatcherScheduler.html
[WorkManager]: https://developer.android.com/topic/libraries/architecture/workmanager/
[Firebase JobDispatcher]: https://github.com/firebase/firebase-jobdispatcher-android
[`DemoDownloadService`]: {{ site.release_v2 }}/demos/main/src/main/java/com/google/android/exoplayer2/demo/DemoDownloadService.java
[`AndroidManifest.xml`]: {{ site.release_v2 }}/demos/main/src/main/AndroidManifest.xml
[`DemoApplication`]: {{ site.release_v2 }}/demos/main/src/main/java/com/google/android/exoplayer2/demo/DemoApplication.java
[`DownloadTracker`]: {{ site.release_v2 }}/demos/main/src/main/java/com/google/android/exoplayer2/demo/DownloadTracker.java
[`PlayerActivity`]: {{ site.release_v2 }}/demos/main/src/main/java/com/google/android/exoplayer2/demo/PlayerActivity.java
[`DownloadService`]: {{ site.release_v2 }}/library/core/src/main/java/com/google/android/exoplayer2/offline/DownloadService.java
[`Requirements`]: {{ site.exo_sdk }}/scheduler/Requirements.html
[further down this page]: #downloading-and-playing-adaptive-streams
[above]: #creating-a-downloadmanager