media3/docs/playlists.md

---
title: Playlists
---

The playlist API is defined by the `Player` interface, which is implemented by
all `ExoPlayer` implementations. It enables sequential playback of multiple
media items. The following example shows how to start playback of a playlist
containing two videos:

~~~
// Build the media items.
MediaItem firstItem = MediaItem.fromUri(firstVideoUri);
MediaItem secondItem = MediaItem.fromUri(secondVideoUri);
// Add the media items to be played.
player.addMediaItem(firstItem);
player.addMediaItem(secondItem);
// Prepare the player.
player.prepare();
// Start the playback.
player.play();
~~~
{: .language-java}

Transitions between items in a playlist are seamless. There's no requirement
that they're of the same format (e.g., it’s fine for a playlist to contain both
H264 and VP9 videos). They may even be of different types (e.g., it’s fine for a
playlist to contain both videos and audio only streams). It's allowed to use the
same `MediaItem` multiple times within a playlist.

## Modifying the playlist ##

It's possible to dynamically modify a playlist by adding, moving and removing
media items. This can be done both before and during playback by calling the
corresponding playlist API methods:

~~~
// Adds a media item at position 1 in the playlist.
player.addMediaItem(/* index= */ 1, MediaItem.fromUri(thirdUri));
// Moves the third media item from position 2 to the start of the playlist.
player.moveMediaItem(/* currentIndex= */ 2, /* newIndex= */ 0);
// Removes the first item from the playlist.
player.removeMediaItem(/* index= */ 0);
~~~
{: .language-java}

Replacing and clearing the entire playlist are also supported:

~~~
// Replaces the playlist with a new one.
List<MediaItem> newItems = ImmutableList.of(
    MediaItem.fromUri(fourthUri),
    MediaItem.fromUri(fifthUri));
player.setMediaItems(newItems, /* resetPosition= */ true);
// Clears the playlist. If prepared, the player transitions to the ended state.
player.clearMediaItems();
~~~
{: .language-java}

The player automatically handles modifications during playback in the correct
way. For example if the currently playing media item is moved, playback is not
interrupted and its new successor will be played upon completion. If the
currently playing `MediaItem` is removed, the player will automatically move to
playing the first remaining successor, or transition to the ended state if no
such successor exists.

## Querying the playlist ##

The playlist can be queried using `Player.getMediaItemCount` and
`Player.getMediaItemAt`. The currently playing media item can be queried
by calling `Player.getCurrentMediaItem`.

## Identifying playlist items ##

To identify playlist items, `MediaItem.mediaId` can be set when building the
item:

~~~
// Build a media item with a media ID.
MediaItem mediaItem =
    new MediaItem.Builder().setUri(uri).setMediaId(mediaId).build();
~~~
{: .language-java}

If an app does not explicitly define a media ID for a media item, the string
representation of the URI is used.

## Associating app data with playlist items ##

In addition to an ID, each media item can also be configured with a custom tag,
which can be any app provided object. One use of custom tags is to attach
metadata to each media item:

~~~
// Build a media item with a custom tag.
MediaItem mediaItem =
    new MediaItem.Builder().setUri(uri).setTag(metadata).build();
~~~
{: .language-java}


## Detecting when playback transitions to another media item ##

When playback transitions to another media item, or starts repeating the same
media item, `Listener.onMediaItemTransition(MediaItem,
@MediaItemTransitionReason)` is called. This callback receives the new media
item, along with a `@MediaItemTransitionReason` indicating why the transition
occurred. A common use case for `onMediaItemTransition` is to update the
application's UI for the new media item:

~~~
@Override
public void onMediaItemTransition(
    @Nullable MediaItem mediaItem, @MediaItemTransitionReason int reason) {
  updateUiForPlayingMediaItem(mediaItem);
}
~~~
{: .language-java}

If the metadata required to update the UI is attached to each media item using
custom tags, then an implementation might look like:

~~~
@Override
public void onMediaItemTransition(
    @Nullable MediaItem mediaItem, @MediaItemTransitionReason int reason) {
  @Nullable CustomMetadata metadata = null;
  if (mediaItem != null && mediaItem.localConfiguration != null) {
    metadata = (CustomMetadata) mediaItem.localConfiguration.tag;
  }
  updateUiForPlayingMediaItem(metadata);
}
~~~
{: .language-java}

## Detecting when the playlist changes ##

When a media item is added, removed or moved,
`Listener.onTimelineChanged(Timeline, @TimelineChangeReason)` is called
immediately with `TIMELINE_CHANGE_REASON_PLAYLIST_CHANGED`. This callback is
called even when the player has not yet been prepared.

~~~
@Override
public void onTimelineChanged(
    Timeline timeline, @TimelineChangeReason int reason) {
  if (reason == TIMELINE_CHANGE_REASON_PLAYLIST_CHANGED) {
    // Update the UI according to the modified playlist (add, move or remove).
    updateUiForPlaylist(timeline);
  }
}
~~~
{: .language-java}

When information such as the duration of a media item in the playlist becomes
available, the `Timeline` will be updated and `onTimelineChanged` will be called
with `TIMELINE_CHANGE_REASON_SOURCE_UPDATE`. Other reasons that can cause a
timeline update include:

* A manifest becoming available after preparing an adaptive media item.
* A manifest being updated periodically during playback of a live stream.

## Setting a custom shuffle order ##

By default the playlist supports shuffling by using the `DefaultShuffleOrder`.
This can be customized by providing a custom shuffle order implementation:

~~~
// Set the custom shuffle order.
simpleExoPlayer.setShuffleOrder(shuffleOrder);
// Enable shuffle mode.
simpleExoPlayer.setShuffleModeEnabled(/* shuffleModeEnabled= */ true);
~~~
{: .language-java}

If the repeat mode of the player is set to `REPEAT_MODE_ALL`, the custom shuffle
order is played in an endless loop.