PlayerController_2.kt

private val _isPlaying = MutableStateFlow(true)
val isPlaying: StateFlow<Boolean> = _isPlaying

private val _playbackState = MutableStateFlow(ExoPlayer.STATE_IDLE)
val playbackState: StateFlow<Int> = _playbackState

private val exoPlayer by lazy {
    SimpleExoPlayer.Builder(context).build().apply {
        addListener(object: Player.EventListener {
            override fun onPlayerStateChanged(playWhenReady: Boolean, playbackState: Int) {
                super.onPlayerStateChanged(playWhenReady, playbackState)
                _playbackState.value = playbackState
                _isPlaying.value = playWhenReady
            }
        })
    }
}