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Version: 11.7.0

How to programmatically detect text track changes on Android

This article describes how you can use the TextTrack API to detect text track changes. A text track "change" is triggered by enabling (or disabling) a subtitle or closed captions track.

Implementing this functionality is a common use-case for developers who want to build their own UI, and annotate the subtitle (or closed captions) track that is currently active.

Usage​

The implementation of the Android SDK applies to all Android-based platforms, including Android TV and Fire TV.

The Android SDK exposes the TextTrack API through player.getTextTracks(). This getTextTracks() method returns a TextTrackList that inherits from the TrackList. This TrackList dispatches the events from the TextTrackListEventTypes. The TextTrackListEventTypes contains the TRACKLISTCHANGE event, as well as the ADDTRACK and REMOVETRACK event.

The code below allows you to detect text track changes.

player.textTracks.addEventListener(TextTrackListEventTypes.TRACKLISTCHANGE) { event ->
    val track = event.track
    val isEnabled = track.mode == TextTrackMode.SHOWING
    println("${track.label}, ${track.kind}, ${track.type}, $isEnabled")
}

The properties of a text track (e.g. mode, kind) are described in the TextTrack and Track API references.

Are you reading this article because you are interested in subtitles and closed captions? Continue reading below.

Refer to how to track ID3 cues if you are interested in timed metadata (ID3, emsg, EventStream, EXT-X-DATERANGE, ...).

Are you reading this article because you are implementing a custom UI? Then you will find the following articles interesting: