# MediaSession.Callback Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) # Callback *** ** * ** *** Kotlin\|[Java](https://developer.android.com/reference/android/media/session/MediaSession.Callback "View this page in Java") ``` abstract class Callback ``` |---|--------------------------------------------------------------------------------------------------------------------------------------------| | [kotlin.Any](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html) || | ↳ | [android.media.session.MediaSession.Callback](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#) | Receives media buttons, transport controls, and commands from controllers and the system. A callback may be set using #setCallback. ## Summary | Public constructors || |------------------------------------------------------------------------------------------------------------------------------|---| | [Callback](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#Callback())`()`
| | Public methods || |----------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onCommand](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onCommand(kotlin.String,%20android.os.Bundle,%20android.os.ResultReceiver))`(`command:` `[String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)`, `args:` `[Bundle](https://developer.android.com/reference/kotlin/android/os/Bundle.html#)?`, `cb:` `[ResultReceiver](https://developer.android.com/reference/kotlin/android/os/ResultReceiver.html#)?`)` Called when a controller has sent a command to this session. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onCustomAction](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onCustomAction(kotlin.String,%20android.os.Bundle))`(`action:` `[String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)`, `extras:` `[Bundle](https://developer.android.com/reference/kotlin/android/os/Bundle.html#)?`)` Called when a[MediaController](https://developer.android.com/reference/kotlin/android/media/session/MediaController)wants a[PlaybackState.CustomAction](https://developer.android.com/reference/kotlin/android/media/session/PlaybackState.CustomAction)to be performed. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onFastForward](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onFastForward())`()` Override to handle requests to fast forward. | | open[Boolean](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html) | [onMediaButtonEvent](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onMediaButtonEvent(android.content.Intent))`(`mediaButtonIntent:` `[Intent](https://developer.android.com/reference/kotlin/android/content/Intent.html#)`)` Called when a media button is pressed and this session has the highest priority or a controller sends a media button event to the session. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onPause](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPause())`()` Override to handle requests to pause playback. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onPlay](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPlay())`()` Override to handle requests to begin playback. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onPlayFromMediaId](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPlayFromMediaId(kotlin.String,%20android.os.Bundle))`(`mediaId:` `[String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)!`, `extras:` `[Bundle](https://developer.android.com/reference/kotlin/android/os/Bundle.html#)!`)` Override to handle requests to play a specific mediaId that was provided by your app's[MediaBrowserService](https://developer.android.com/reference/kotlin/android/service/media/MediaBrowserService.html#). | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onPlayFromSearch](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPlayFromSearch(kotlin.String,%20android.os.Bundle))`(`query:` `[String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)!`, `extras:` `[Bundle](https://developer.android.com/reference/kotlin/android/os/Bundle.html#)!`)` Override to handle requests to begin playback from a search query. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onPlayFromUri](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPlayFromUri(android.net.Uri,%20android.os.Bundle))`(`uri:` `[Uri](https://developer.android.com/reference/kotlin/android/net/Uri.html#)!`, `extras:` `[Bundle](https://developer.android.com/reference/kotlin/android/os/Bundle.html#)!`)` Override to handle requests to play a specific media item represented by a URI. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onPrepare](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPrepare())`()` Override to handle requests to prepare playback. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onPrepareFromMediaId](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPrepareFromMediaId(kotlin.String,%20android.os.Bundle))`(`mediaId:` `[String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)!`, `extras:` `[Bundle](https://developer.android.com/reference/kotlin/android/os/Bundle.html#)!`)` Override to handle requests to prepare for playing a specific mediaId that was provided by your app's[MediaBrowserService](https://developer.android.com/reference/kotlin/android/service/media/MediaBrowserService.html#). | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onPrepareFromSearch](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPrepareFromSearch(kotlin.String,%20android.os.Bundle))`(`query:` `[String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)!`, `extras:` `[Bundle](https://developer.android.com/reference/kotlin/android/os/Bundle.html#)!`)` Override to handle requests to prepare playback from a search query. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onPrepareFromUri](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPrepareFromUri(android.net.Uri,%20android.os.Bundle))`(`uri:` `[Uri](https://developer.android.com/reference/kotlin/android/net/Uri.html#)!`, `extras:` `[Bundle](https://developer.android.com/reference/kotlin/android/os/Bundle.html#)!`)` Override to handle requests to prepare a specific media item represented by a URI. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onRewind](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onRewind())`()` Override to handle requests to rewind. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onSeekTo](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onSeekTo(kotlin.Long))`(`pos:` `[Long](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-long/index.html)`)` Override to handle requests to seek to a specific position in ms. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onSetPlaybackSpeed](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onSetPlaybackSpeed(kotlin.Float))`(`speed:` `[Float](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-float/index.html)`)` Override to handle the playback speed change. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onSetRating](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onSetRating(android.media.Rating))`(`rating:` `[Rating](https://developer.android.com/reference/kotlin/android/media/Rating.html#)`)` Override to handle the item being rated. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onSkipToNext](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onSkipToNext())`()` Override to handle requests to skip to the next media item. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onSkipToPrevious](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onSkipToPrevious())`()` Override to handle requests to skip to the previous media item. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onSkipToQueueItem](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onSkipToQueueItem(kotlin.Long))`(`id:` `[Long](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-long/index.html)`)` Override to handle requests to play an item with a given id from the play queue. | | open[Unit](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) | [onStop](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onStop())`()` Override to handle requests to stop playback. | ## Public constructors ### Callback Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` Callback() ``` ## Public methods ### onCommand Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onCommand(     command: String,     args: Bundle?,     cb: ResultReceiver? ): Unit ``` Called when a controller has sent a command to this session. The owner of the session may handle custom commands but is not required to. | Parameters || |-----------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | `command` | [String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html):The command name. This value cannot be`null`. | | `args` | [Bundle](https://developer.android.com/reference/kotlin/android/os/Bundle.html#)?:Optional parameters for the command, may be null. | | `cb` | [ResultReceiver](https://developer.android.com/reference/kotlin/android/os/ResultReceiver.html#)?:A result receiver to which a result may be sent by the command, may be null. | ### onCustomAction Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onCustomAction(     action: String,     extras: Bundle? ): Unit ``` Called when a[MediaController](https://developer.android.com/reference/kotlin/android/media/session/MediaController)wants a[PlaybackState.CustomAction](https://developer.android.com/reference/kotlin/android/media/session/PlaybackState.CustomAction)to be performed. | Parameters || |----------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | `action` | [String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html):The action that was originally sent in the[PlaybackState.CustomAction](https://developer.android.com/reference/kotlin/android/media/session/PlaybackState.CustomAction). This value cannot be`null`. | | `extras` | [Bundle](https://developer.android.com/reference/kotlin/android/os/Bundle.html#)?:Optional extras specified by the[MediaController](https://developer.android.com/reference/kotlin/android/media/session/MediaController). This value may be`null`. | ### onFastForward Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onFastForward(): Unit ``` Override to handle requests to fast forward. ### onMediaButtonEvent Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onMediaButtonEvent(mediaButtonIntent: Intent): Boolean ``` Called when a media button is pressed and this session has the highest priority or a controller sends a media button event to the session. The default behavior will call the relevant method if the action for it was set. The intent will be of type[Intent.ACTION_MEDIA_BUTTON](https://developer.android.com/reference/kotlin/android/content/Intent.html#ACTION_MEDIA_BUTTON:kotlin.String)with a KeyEvent in[Intent.EXTRA_KEY_EVENT](https://developer.android.com/reference/kotlin/android/content/Intent.html#EXTRA_KEY_EVENT:kotlin.String) | Parameters || |---------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------| | `mediaButtonIntent` | [Intent](https://developer.android.com/reference/kotlin/android/content/Intent.html#):an intent containing the KeyEvent as an extra This value cannot be`null`. | | Return || |------------------------------------------------------------------------------------|-------------------------------------------------| | [Boolean](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-boolean/index.html) | True if the event was handled, false otherwise. | ### onPause Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onPause(): Unit ``` Override to handle requests to pause playback. ### onPlay Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onPlay(): Unit ``` Override to handle requests to begin playback. ### onPlayFromMediaId Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onPlayFromMediaId(     mediaId: String!,     extras: Bundle! ): Unit ``` Override to handle requests to play a specific mediaId that was provided by your app's[MediaBrowserService](https://developer.android.com/reference/kotlin/android/service/media/MediaBrowserService.html#). ### onPlayFromSearch Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onPlayFromSearch(     query: String!,     extras: Bundle! ): Unit ``` Override to handle requests to begin playback from a search query. An empty query indicates that the app may play any music. The implementation should attempt to make a smart choice about what to play. ### onPlayFromUri Added in[API level 23](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onPlayFromUri(     uri: Uri!,     extras: Bundle! ): Unit ``` Override to handle requests to play a specific media item represented by a URI. ### onPrepare Added in[API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onPrepare(): Unit ``` Override to handle requests to prepare playback. During the preparation, a session should not hold audio focus in order to allow other sessions play seamlessly. The state of playback should be updated to[PlaybackState.STATE_PAUSED](https://developer.android.com/reference/kotlin/android/media/session/PlaybackState#STATE_PAUSED:kotlin.Int)after the preparation is done. ### onPrepareFromMediaId Added in[API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onPrepareFromMediaId(     mediaId: String!,     extras: Bundle! ): Unit ``` Override to handle requests to prepare for playing a specific mediaId that was provided by your app's[MediaBrowserService](https://developer.android.com/reference/kotlin/android/service/media/MediaBrowserService.html#). During the preparation, a session should not hold audio focus in order to allow other sessions play seamlessly. The state of playback should be updated to[PlaybackState.STATE_PAUSED](https://developer.android.com/reference/kotlin/android/media/session/PlaybackState#STATE_PAUSED:kotlin.Int)after the preparation is done. The playback of the prepared content should start in the implementation of[onPlay](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPlay()). Override[onPlayFromMediaId](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPlayFromMediaId(kotlin.String,%20android.os.Bundle))to handle requests for starting playback without preparation. ### onPrepareFromSearch Added in[API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onPrepareFromSearch(     query: String!,     extras: Bundle! ): Unit ``` Override to handle requests to prepare playback from a search query. An empty query indicates that the app may prepare any music. The implementation should attempt to make a smart choice about what to play. During the preparation, a session should not hold audio focus in order to allow other sessions play seamlessly. The state of playback should be updated to[PlaybackState.STATE_PAUSED](https://developer.android.com/reference/kotlin/android/media/session/PlaybackState#STATE_PAUSED:kotlin.Int)after the preparation is done. The playback of the prepared content should start in the implementation of[onPlay](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPlay()). Override[onPlayFromSearch](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPlayFromSearch(kotlin.String,%20android.os.Bundle))to handle requests for starting playback without preparation. ### onPrepareFromUri Added in[API level 24](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onPrepareFromUri(     uri: Uri!,     extras: Bundle! ): Unit ``` Override to handle requests to prepare a specific media item represented by a URI. During the preparation, a session should not hold audio focus in order to allow other sessions play seamlessly. The state of playback should be updated to[PlaybackState.STATE_PAUSED](https://developer.android.com/reference/kotlin/android/media/session/PlaybackState#STATE_PAUSED:kotlin.Int)after the preparation is done. The playback of the prepared content should start in the implementation of[onPlay](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPlay()). Override[onPlayFromUri](https://developer.android.com/reference/kotlin/android/media/session/MediaSession.Callback#onPlayFromUri(android.net.Uri,%20android.os.Bundle))to handle requests for starting playback without preparation. ### onRewind Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onRewind(): Unit ``` Override to handle requests to rewind. ### onSeekTo Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onSeekTo(pos: Long): Unit ``` Override to handle requests to seek to a specific position in ms. | Parameters || |-------|------------------------------------------------------------------------------------------------------------------------| | `pos` | [Long](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-long/index.html):New position to move to, in milliseconds. | ### onSetPlaybackSpeed Added in[API level 29](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onSetPlaybackSpeed(speed: Float): Unit ``` Override to handle the playback speed change. To update the new playback speed, create a new[PlaybackState](https://developer.android.com/reference/kotlin/android/media/session/PlaybackState)by using[android.media.session.PlaybackState.Builder#setState(int,long,float)](https://developer.android.com/reference/kotlin/android/media/session/PlaybackState.Builder#setState(kotlin.Int,%20kotlin.Long,%20kotlin.Float)), and set it with[setPlaybackState(android.media.session.PlaybackState)](https://developer.android.com/reference/kotlin/android/media/session/MediaSession#setPlaybackState(android.media.session.PlaybackState)). A value of`1.0f`is the default playback value, and a negative value indicates reverse playback. The`speed`will not be equal to zero. | Parameters || |---------|---------------------------------------------------------------------------------------------------| | `speed` | [Float](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-float/index.html):the playback speed | **See Also** - [#setPlaybackState(PlaybackState)](https://developer.android.com/reference/kotlin/android/media/session/MediaSession#setPlaybackState(android.media.session.PlaybackState)) - [android.media.session.PlaybackState.Builder#setState(int, long, float)](https://developer.android.com/reference/kotlin/android/media/session/PlaybackState.Builder#setState(kotlin.Int,%20kotlin.Long,%20kotlin.Float)) ### onSetRating Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onSetRating(rating: Rating): Unit ``` Override to handle the item being rated. | Parameters || |----------|-----------------------------------------------------------------------------------------------------------------| | `rating` | [Rating](https://developer.android.com/reference/kotlin/android/media/Rating.html#):This value cannot be`null`. | ### onSkipToNext Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onSkipToNext(): Unit ``` Override to handle requests to skip to the next media item. ### onSkipToPrevious Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onSkipToPrevious(): Unit ``` Override to handle requests to skip to the previous media item. ### onSkipToQueueItem Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onSkipToQueueItem(id: Long): Unit ``` Override to handle requests to play an item with a given id from the play queue. ### onStop Added in[API level 21](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` open fun onStop(): Unit ``` Override to handle requests to stop playback.