question: public void selectTrack ( int index ) { selectedTrackIndex = index ; ExposedTrack selectedTrack = tracks . get ( selectedTrackIndex ) ; selectedVariantIndex = selectedTrack . defaultVariantIndex ; variants = selectedTrack . variants ; variantPlaylists = new HlsMediaPlaylist [ variants . length ] ; variantLastPlaylistLoadTimesMs = new long [ variants . length ] ; variantBlacklistTimes = new long [ variants . length ] ; }
target:  Selects a track for use. <p> This method should only be called after the source has been prepared.