SessionPlayer

BUFFERING_STATE_BUFFERING_AND_PLAYABLE

static val BUFFERING_STATE_BUFFERING_AND_PLAYABLE: Int

Buffering state indicating the player is buffering but enough has been buffered for this player to be able to play the content. See getBufferedPosition() for how far is buffered already.

Value: 1

BUFFERING_STATE_BUFFERING_AND_STARVED

static val BUFFERING_STATE_BUFFERING_AND_STARVED: Int

Buffering state indicating the player is buffering, but the player is currently starved for data, and cannot play.

Value: 2

BUFFERING_STATE_COMPLETE

static val BUFFERING_STATE_COMPLETE: Int

Buffering state indicating the player is done buffering, and the remainder of the content is available for playback.

Value: 3

BUFFERING_STATE_UNKNOWN

static val BUFFERING_STATE_UNKNOWN: Int

Buffering state is unknown.

Value: 0

INVALID_ITEM_INDEX

static val INVALID_ITEM_INDEX: Int

Media item index is invalid. This value will be returned when the corresponding media item does not exist.

Value: -1

PLAYER_STATE_ERROR

static val PLAYER_STATE_ERROR: Int

State when the player is in error state and cannot be recovered self.

Value: 3

PLAYER_STATE_IDLE

static val PLAYER_STATE_IDLE: Int

State when the player is idle, and needs configuration to start playback.

Value: 0

PLAYER_STATE_PAUSED

static val PLAYER_STATE_PAUSED: Int

State when the player's playback is paused

Value: 1

PLAYER_STATE_PLAYING

static val PLAYER_STATE_PLAYING: Int

State when the player's playback is ongoing

Value: 2

REPEAT_MODE_ALL

static val REPEAT_MODE_ALL: Int

Playing media list will be repeated.

Value: 2

REPEAT_MODE_GROUP

static val REPEAT_MODE_GROUP: Int

Playback of the playing media group will be repeated. A group is a logical block of media items which is specified in the section 5.7 of the Bluetooth AVRCP 1.6. An example of a group is the playlist.

Value: 3

REPEAT_MODE_NONE

static val REPEAT_MODE_NONE: Int

Playback will be stopped at the end of the playing media list.

Value: 0

REPEAT_MODE_ONE

static val REPEAT_MODE_ONE: Int

Playback of the current playing media item will be repeated.

Value: 1

SHUFFLE_MODE_ALL

static val SHUFFLE_MODE_ALL: Int

Media list will be played in shuffled order.

Value: 1

SHUFFLE_MODE_GROUP

static val SHUFFLE_MODE_GROUP: Int

Media group will be played in shuffled order. A group is a logical block of media items which is specified in the section 5.7 of the Bluetooth AVRCP 1.6. An example of a group is the playlist.

Value: 2

SHUFFLE_MODE_NONE

static val SHUFFLE_MODE_NONE: Int

Media list will be played in order.

Value: 0

UNKNOWN_TIME

static val UNKNOWN_TIME: Long

Value indicating the time is unknown

Value: Long.MIN_VALUE

<init>

SessionPlayer()

Base interface for all media players that want media session.

APIs that return ListenableFuture should be the asynchronous calls and shouldn't block the calling thread. This guarantees the APIs are safe to be called on the main thread.

Topics covered here are:

1. Best practices
2. Player states
3. Invalid method calls

Best practices

• When updating UI, you should respond to PlayerCallback invocations instead of PlayerResult objects since the player can be controlled by others.
• When a SessionPlayer object is no longer being used, call #close() as soon as possible to release the resources used by the internal player engine associated with the SessionPlayer. For example, if a player uses hardware decoder, other player instances may fallback to software decoders or fail to play. You cannot use SessionPlayer instance after you call #close(). There is no way to reuse the instance.
• The current playback position can be retrieved with a call to getCurrentPosition(), which is helpful for applications such as a music player that need to keep track of the playback progress.
• The playback position can be adjusted with a call to seekTo(long). Although the asynchronous seekTo call returns right away, the actual seek operation may take a while to finish, especially for audio/video being streamed.
• You can call seekTo(long) from the PLAYER_STATE_PAUSED. In these cases, if you are playing a video stream and the requested position is valid, one video frame may be displayed.

Player states

1. PLAYER_STATE_IDLE: Initial state after the instantiation.

   While in this state, you should call setMediaItem(MediaItem) or setPlaylist(List, MediaMetadata). Check returned ListenableFuture for potential error.

   Calling prepare() transfers this object to PLAYER_STATE_PAUSED.

2. PLAYER_STATE_PAUSED: State when the audio/video playback is paused.

   Call play() to resume or start playback from the position where it paused.

3. PLAYER_STATE_PLAYING: State when the player plays the media item.

   In this state, PlayerCallback#onBufferingStateChanged( * SessionPlayer, MediaItem, int) will be called regularly to tell the buffering status.

   Playback state would remain PLAYER_STATE_PLAYING when the currently playing media item is changed.

   When the playback reaches the end of stream, the behavior depends on repeat mode, set by setRepeatMode(int). If the repeat mode was set to REPEAT_MODE_NONE, the player will transfer to the PLAYER_STATE_PAUSED. Otherwise, the SessionPlayer object remains in the PLAYER_STATE_PLAYING and playback will be ongoing.

4. PLAYER_STATE_ERROR: State when the playback failed and player cannot be recovered by itself.

   In general, playback might fail due to various reasons such as unsupported audio/video format, poorly interleaved audio/video, resolution too high, streaming timeout, and others. In addition, due to programming errors, a playback control operation might be performed from an invalid state. In these cases the player may transition to this state.

Invalid method calls

Subclasses of the SessionPlayer may have extra methods that are safe to be called in the error state and/or provide a method to recover from the error state. Take a look at documentations of specific subclass that you're interested in.

Most methods can be called from any non-Error state. In case they're called in invalid state, the implementation should ignore and would return PlayerResult with PlayerResult#RESULT_ERROR_INVALID_STATE. The following table lists the methods that aren't guaranteed to successfully running if they're called from the associated invalid states.

addPlaylistItem

@NonNull abstract fun addPlaylistItem(
    index: Int, 
    @NonNull item: MediaItem
): ListenableFuture<SessionPlayer.PlayerResult!>

Adds the media item to the playlist at the index. Index equals to or greater than the current playlist size (e.g. Integer#MAX_VALUE) will add the item at the end of the playlist.

If index is less than or equal to the current index of the playlist, the current index of the playlist should be increased correspondingly.

The implementation must notify registered callbacks with PlayerCallback#onPlaylistChanged(SessionPlayer, List, MediaMetadata) when it's completed.

The implementation must close the ParcelFileDescriptor in the FileMediaItem if the given media item is a FileMediaItem.

On success, a PlayerResult should be returned with item added.

close

@CallSuper open fun close(): Unit

Removes all existing references to callbacks and executors. Note: Sub classes of SessionPlayer that override this API should call this super method.

deselectTrack

@NonNull open fun deselectTrack(@NonNull trackInfo: SessionPlayer.TrackInfo): ListenableFuture<SessionPlayer.PlayerResult!>

Deselects the TrackInfo for the current media item.

Generally, a track should already be selected in order to be deselected, and audio and video tracks should not be deselected.

The types of tracks supported may vary based on player implementation.

Note: getSelectedTrack(int) returns the currently selected track per track type that can be deselected, but the list may be invalidated when PlayerCallback#onTracksChanged(SessionPlayer, List) is called.

getAudioAttributes

@Nullable abstract fun getAudioAttributes(): AudioAttributesCompat?

Gets the AudioAttributesCompat that media player has.

getBufferedPosition

abstract fun getBufferedPosition(): Long

Gets the position for how much has been buffered, or UNKNOWN_TIME if unknown.

The position is the relative position based on the MediaItem#getStartPosition(). So the position 0 means the start position of the MediaItem.

getBufferingState

abstract fun getBufferingState(): Int

Returns the current buffering state of the player.

During the buffering, see getBufferedPosition() for the quantifying the amount already buffered.

getCurrentMediaItem

@Nullable abstract fun getCurrentMediaItem(): MediaItem?

Gets the current media item, which is currently playing or would be played with later play. This value may be updated when PlayerCallback#onCurrentMediaItemChanged(SessionPlayer, MediaItem) or PlayerCallback#onPlaylistChanged(SessionPlayer, List, MediaMetadata) is called.

getCurrentMediaItemIndex

@IntRange(-1) abstract fun getCurrentMediaItemIndex(): Int

Gets the index of current media item in playlist. This value should be updated when PlayerCallback#onCurrentMediaItemChanged(SessionPlayer, MediaItem) or PlayerCallback#onPlaylistChanged(SessionPlayer, List, MediaMetadata) is called.

getCurrentPosition

abstract fun getCurrentPosition(): Long

Gets the current playback position.

The position is the relative position based on the MediaItem#getStartPosition(). So the position 0 means the start position of the MediaItem.

getDuration

abstract fun getDuration(): Long

Gets the duration of the current media item, or UNKNOWN_TIME if unknown. If the current MediaItem has either start or end position, then duration would be adjusted accordingly instead of returning the whole size of the MediaItem.

getNextMediaItemIndex

@IntRange(-1) abstract fun getNextMediaItemIndex(): Int

Gets the next item index in the playlist. This value should be updated when PlayerCallback#onCurrentMediaItemChanged(SessionPlayer, MediaItem) or PlayerCallback#onPlaylistChanged(SessionPlayer, List, MediaMetadata) is called.

getPlaybackSpeed

abstract fun getPlaybackSpeed(): Float

Gets the actual playback speed to be used by the player when playing. A value of 1.0f is the default playback value, and a negative value indicates reverse playback.

Note that it may differ from the speed set in setPlaybackSpeed(float).

getPlayerState

abstract fun getPlayerState(): Int

Gets the current player state.

getPlaylist

@Nullable abstract fun getPlaylist(): MutableList<MediaItem!>?

Gets the playlist. It can be null if the playlist hasn't been set or it's reset by setMediaItem.

getPlaylistMetadata

@Nullable abstract fun getPlaylistMetadata(): MediaMetadata?

Gets the playlist metadata.

getPreviousMediaItemIndex

@IntRange(-1) abstract fun getPreviousMediaItemIndex(): Int

Gets the previous item index in the playlist. This value should be updated when PlayerCallback#onCurrentMediaItemChanged(SessionPlayer, MediaItem) or PlayerCallback#onPlaylistChanged(SessionPlayer, List, MediaMetadata) is called.

getRepeatMode

abstract fun getRepeatMode(): Int

Gets the repeat mode.

getSelectedTrack

@Nullable open fun getSelectedTrack(trackType: Int): SessionPlayer.TrackInfo?

Gets currently selected track's TrackInfo for the given track type.

The returned value can be outdated after PlayerCallback#onTracksChanged(SessionPlayer, List), PlayerCallback#onTrackSelected(SessionPlayer, TrackInfo), or PlayerCallback#onTrackDeselected(SessionPlayer, TrackInfo) is called.

getShuffleMode

abstract fun getShuffleMode(): Int

Gets the shuffle mode.

getTracks

@NonNull open fun getTracks(): MutableList<SessionPlayer.TrackInfo!>

Gets the full list of selected and unselected tracks that the media contains. The order of the list is irrelevant as different players expose tracks in different ways, but the tracks will generally be ordered based on track type.

The types of tracks supported may vary based on player implementation.

getVideoSize

@NonNull open fun getVideoSize(): VideoSize

Gets the size of the video.

movePlaylistItem

@NonNull open fun movePlaylistItem(
    @IntRange(0) fromIndex: Int, 
    @IntRange(0) toIndex: Int
): ListenableFuture<SessionPlayer.PlayerResult!>

Moves the media item at fromIdx to toIdx in the playlist.

The implementation must notify registered callbacks with PlayerCallback#onPlaylistChanged(SessionPlayer, List, MediaMetadata) when it's completed.

On success, a PlayerResult should be returned with item set.

pause

@NonNull abstract fun pause(): ListenableFuture<SessionPlayer.PlayerResult!>

Pauses playback.

On success, this transfers the player state to PLAYER_STATE_PAUSED and a PlayerResult should be returned with the current media item when the command was completed. If it is called in PLAYER_STATE_IDLE or PLAYER_STATE_ERROR, it should be ignored and a PlayerResult should be returned with PlayerResult#RESULT_ERROR_INVALID_STATE.

play

@NonNull abstract fun play(): ListenableFuture<SessionPlayer.PlayerResult!>

Starts or resumes playback.

On success, this transfers the player state to PLAYER_STATE_PLAYING and a PlayerResult should be returned with the current media item when the command was completed. If it is called in PLAYER_STATE_IDLE or PLAYER_STATE_ERROR, it should be ignored and a PlayerResult should be returned with PlayerResult#RESULT_ERROR_INVALID_STATE.

prepare

@NonNull abstract fun prepare(): ListenableFuture<SessionPlayer.PlayerResult!>

Prepares the media items for playback. During this time, the player may allocate resources required to play, such as audio and video decoders. Before calling this API, set media item(s) through either setMediaItem or setPlaylist.

On success, this transfers the player state from PLAYER_STATE_IDLE to PLAYER_STATE_PAUSED and a PlayerResult should be returned with the prepared media item when the command completed. If it's not called in PLAYER_STATE_IDLE, it should be ignored and PlayerResult should be returned with PlayerResult#RESULT_ERROR_INVALID_STATE.

registerPlayerCallback

fun registerPlayerCallback(
    @NonNull executor: Executor, 
    @NonNull callback: SessionPlayer.PlayerCallback
): Unit

Register PlayerCallback to listen changes.

removePlaylistItem

@NonNull abstract fun removePlaylistItem(@IntRange(0) index: Int): ListenableFuture<SessionPlayer.PlayerResult!>

Removes the media item from the playlist

The implementation must notify registered callbacks with PlayerCallback#onPlaylistChanged(SessionPlayer, List, MediaMetadata) when it's completed.

On success, a PlayerResult should be returned with item removed.

replacePlaylistItem

@NonNull abstract fun replacePlaylistItem(
    index: Int, 
    @NonNull item: MediaItem
): ListenableFuture<SessionPlayer.PlayerResult!>

Replaces the media item at index in the playlist. This can be also used to update metadata of an item.

The implementation must notify registered callbacks with PlayerCallback#onPlaylistChanged(SessionPlayer, List, MediaMetadata) when it's completed.

The implementation must close the ParcelFileDescriptor in the FileMediaItem if the given media item is a FileMediaItem.

On success, a PlayerResult should be returned with item set.

seekTo

@NonNull abstract fun seekTo(position: Long): ListenableFuture<SessionPlayer.PlayerResult!>

Seeks to the specified position.

The position is the relative position based on the MediaItem#getStartPosition(). So calling seekTo(long) with 0 means the seek to the start position.

On success, a PlayerResult should be returned with the current media item when the command completed. If it's called in PLAYER_STATE_IDLE, it is ignored and a PlayerResult should be returned with PlayerResult#RESULT_ERROR_INVALID_STATE.

selectTrack

@NonNull open fun selectTrack(@NonNull trackInfo: SessionPlayer.TrackInfo): ListenableFuture<SessionPlayer.PlayerResult!>

Selects the TrackInfo for the current media item.

Generally one track will be selected for each track type.

The types of tracks supported may vary based on player implementation.

Note: getTracks() returns the list of tracks that can be selected, but the list may be invalidated when PlayerCallback#onTracksChanged(SessionPlayer, List) is called.

setAudioAttributes

@NonNull abstract fun setAudioAttributes(@NonNull attributes: AudioAttributesCompat): ListenableFuture<SessionPlayer.PlayerResult!>

Sets the AudioAttributesCompat to be used during the playback of the media.

You must call this method in PLAYER_STATE_IDLE in order for the audio attributes to become effective thereafter. Otherwise, the call would be ignored and PlayerResult should be returned with PlayerResult#RESULT_ERROR_INVALID_STATE.

On success, a PlayerResult should be returned with the current media item when the command completed.

setMediaItem

@NonNull abstract fun setMediaItem(@NonNull item: MediaItem): ListenableFuture<SessionPlayer.PlayerResult!>

Sets a MediaItem for playback. Use this or setPlaylist to specify which items to play. If you want to change current item in the playlist, use one of skipToPlaylistItem, skipToNextPlaylistItem, or skipToPreviousPlaylistItem instead of this method.

This can be called multiple times in any states other than PLAYER_STATE_ERROR. This would override previous setMediaItem or setPlaylist calls.

It's recommended to fill MediaMetadata in MediaItem especially for the duration information with the key MediaMetadata#METADATA_KEY_DURATION. Without the duration information in the metadata, session will do extra work to get the duration and send it to the controller.

The implementation must notify registered callbacks with PlayerCallback#onPlaylistChanged and PlayerCallback#onCurrentMediaItemChanged when it's completed. The current item would be the item given here.

The implementation must close the ParcelFileDescriptor in the FileMediaItem if the given media item is a FileMediaItem.

On success, a PlayerResult should be returned with item set.

setPlaybackSpeed

@NonNull abstract fun setPlaybackSpeed(playbackSpeed: Float): ListenableFuture<SessionPlayer.PlayerResult!>

Sets the playback speed. The default playback speed is 1.0f, and negative values indicate reverse playback and 0.0f is not allowed.

The supported playback speed range depends on the underlying player implementation, so it is recommended to query the actual speed of the player via getPlaybackSpeed() after the operation completes. In particular, please note that player implementations may not support reverse playback.

On success, a PlayerResult should be returned with the current media item when the command completed.

setPlaylist

@NonNull abstract fun setPlaylist(
    @NonNull list: MutableList<MediaItem!>, 
    @Nullable metadata: MediaMetadata?
): ListenableFuture<SessionPlayer.PlayerResult!>

Sets a list of MediaItem with metadata. Use this or setMediaItem to specify which items to play.

This can be called multiple times in any states other than PLAYER_STATE_ERROR. This would override previous setMediaItem or setPlaylist calls.

Ensure uniqueness of each MediaItem in the playlist so the session can uniquely identity individual items. All MediaItems shouldn't be null as well.

It's recommended to fill MediaMetadata in each MediaItem especially for the duration information with the key MediaMetadata#METADATA_KEY_DURATION. Without the duration information in the metadata, session will do extra work to get the duration and send it to the controller.

The implementation must notify registered callbacks with PlayerCallback#onPlaylistChanged and PlayerCallback#onCurrentMediaItemChanged when it's completed. The current media item would be the first item in the playlist.

The implementation must close the ParcelFileDescriptor in the FileMediaItem when a media item in the playlist is a FileMediaItem.

On success, a PlayerResult should be returned with the first media item of the playlist when the command completed.

setRepeatMode

@NonNull abstract fun setRepeatMode(repeatMode: Int): ListenableFuture<SessionPlayer.PlayerResult!>

Sets the repeat mode.

The implementation must notify registered callbacks with PlayerCallback#onRepeatModeChanged(SessionPlayer, int) when it's completed.

On success, a PlayerResult should be returned with the current media item when the command completed.

setShuffleMode

@NonNull abstract fun setShuffleMode(shuffleMode: Int): ListenableFuture<SessionPlayer.PlayerResult!>

Sets the shuffle mode.

The implementation must notify registered callbacks with PlayerCallback#onShuffleModeChanged(SessionPlayer, int) when it's completed.

On success, a PlayerResult should be returned with the current media item when the command completed.

setSurface

@NonNull open fun setSurface(@Nullable surface: Surface?): ListenableFuture<SessionPlayer.PlayerResult!>

Sets the Surface to be used as the sink for the video portion of the media.

A null surface will reset any Surface and result in only the audio track being played.

On success, a SessionPlayer.PlayerResult is returned with the current media item when the command completed.

skipToNextPlaylistItem

@NonNull abstract fun skipToNextPlaylistItem(): ListenableFuture<SessionPlayer.PlayerResult!>

Skips to the next item in the playlist.

The implementation must notify registered callbacks with PlayerCallback#onCurrentMediaItemChanged(SessionPlayer, MediaItem) when it's completed.

On success, a PlayerResult should be returned with the current media item when the command completed.

skipToPlaylistItem

@NonNull abstract fun skipToPlaylistItem(@IntRange(0) index: Int): ListenableFuture<SessionPlayer.PlayerResult!>

Skips to the item in the playlist at the index.

The implementation must notify registered callbacks with PlayerCallback#onCurrentMediaItemChanged(SessionPlayer, MediaItem) when it's completed.

On success, a PlayerResult should be returned with the current media item when the command completed.

skipToPreviousPlaylistItem

@NonNull abstract fun skipToPreviousPlaylistItem(): ListenableFuture<SessionPlayer.PlayerResult!>

Skips to the previous item in the playlist.

The implementation must notify registered callbacks with PlayerCallback#onCurrentMediaItemChanged(SessionPlayer, MediaItem) when it's completed.

On success, a PlayerResult should be returned with the current media item when the command completed.

unregisterPlayerCallback

fun unregisterPlayerCallback(@NonNull callback: SessionPlayer.PlayerCallback): Unit

Unregister the previously registered PlayerCallback.

updatePlaylistMetadata

@NonNull abstract fun updatePlaylistMetadata(@Nullable metadata: MediaMetadata?): ListenableFuture<SessionPlayer.PlayerResult!>

Updates the playlist metadata while keeping the playlist as-is.

The implementation must notify registered callbacks with PlayerCallback#onPlaylistMetadataChanged(SessionPlayer, MediaMetadata) when it's completed.

On success, a PlayerResult should be returned with the current media item when the command completed.

getCallbacks

@NonNull protected fun getCallbacks(): MutableList<Pair<SessionPlayer.PlayerCallback!, Executor!>!>

Gets the callbacks with executors for subclasses to notify player events.