Player

public interface Player

A media player interface defining high-level functionality, such as the ability to play, pause, seek and query properties of the currently playing media.

Player features and usage

Some important properties of media players that implement this interface are:

• All methods must be called from a single application thread unless indicated otherwise. Callbacks in registered listeners are called on the same thread.
• The available functionality can be limited. Player instances provide a set of available commands to signal feature support and users of the interface must only call methods if the corresponding Command is available.
• Users can register Player.Listener callbacks that get informed about state changes.
• Player instances need to update the visible state immediately after each method call, even if the actual changes are handled on background threads or even other devices. This simplifies the usage for callers of methods as no asynchronous handling needs to be considered.
• Player instances can provide playlist operations, like 'set', 'add', 'remove', 'move' or 'replace' of MediaItem instances. The player can also support repeat modes and shuffling within this playlist. The player provides a representing the structure of the playlist and all its items, which can be obtained by calling getCurrentTimeline
• Player instances can provide seeking within the currently playing item and to other items, using the various seek... methods.
• Player instances can provide Tracks defining the currently available and selected tracks, which can be obtained by calling getCurrentTracks. Users can also modify track selection behavior by setting TrackSelectionParameters with setTrackSelectionParameters.
• Player instances can provide MediaMetadata about the currently playing item, which can be obtained by calling getMediaMetadata.
• Player instances can provide information about ads in its media structure, for example via isPlayingAd.
• Player instances can accept different types of video outputs, like SurfaceView or TextureView for video rendering.
• Player instances can handle playback speed, audio attributes, and audio volume.
• Player instances can provide information about the playback device, which may be remote, and allow to change the device's volume.

API stability guarantees

The majority of the Player interface and its related classes are part of the stable API that guarantees backwards-compatibility for users of the API. Only more advances use cases may need to rely on UnstableApi classes and methods that are subject to incompatible changes or even removal in a future release. Implementors of the Player interface are not covered by these API stability guarantees.

Player state

Users can listen to state changes by adding a Player.Listener with addListener.

The main elements of the overall player state are:

• Playlist
  • MediaItem instances can be added with methods like setMediaItem to define what the player will be playing.
  • The current playlist can be obtained via getCurrentTimeline and convenience methods like getMediaItemCount or getCurrentMediaItem.
  • With an empty playlist, the player can only be in STATE_IDLE or STATE_ENDED.
• Playback state
  • STATE_IDLE: This is the initial state, the state when the player is stopped, and when playback failed. The player will hold only limited resources in this state. prepare must be called to transition away from this state.
  • STATE_BUFFERING: The player is not able to immediately play from its current position. This mostly happens because more data needs to be loaded.
  • STATE_READY: The player is able to immediately play from its current position.
  • STATE_ENDED: The player finished playing all media, or there is no media to play.
• Play/Pause, playback suppression and isPlaying
  • playWhenReady: Indicates the user intention to play. It can be set with play or pause.
  • playback suppression: Defines a reason for which playback will be suppressed even if playWhenReady is true.
  • isPlaying: Whether the player is playing (that is, its position is advancing and media is being presented). This will only be true if playback state is STATE_READY, playWhenReady is true, and playback is not suppressed.
• Playback position
  • media item index: The index in the playlist.
  • ad insertion: Whether an inserted ad is playing and which ad group index and ad index in the group it belongs to
  • current position: The current position of the playback. This is the same as the content position unless an ad is playing, where this indicates the position in the inserted ad.

Note that there are no callbacks for normal playback progression, only for transitions between media items and other position discontinuities. Code that needs to monitor playback progress (for example, an UI progress bar) should query the current position in appropriate intervals.

Implementing the Player interface

Implementing the Player interface is complex, as the interface includes many convenience methods that need to provide a consistent state and behavior, requires correct handling of listeners and available commands, and expects immediate state changes even if methods are internally handled asynchronously. For this reason, implementations are advised to inherit that handles all of these complexities and provides a simpler integration point for implementors of the interface.

Summary