class PlayerHolder(...) : AnkoLogger {
    ...
    fun start() {
        // Load media.
        player.prepare(...)
        // Restore state (after onResume()/onStart())
        with(playerState) {
            // Start playback when media has buffered enough
            // (whenReady is true by default).
            player.playWhenReady = whenReady
            player.seekTo(window, position)
        }
        info { "SimpleExoPlayer is started" }
    }

    fun stop() {
        with(player) {
            // Save state
            with(state) {
                position = currentPosition
                window = currentWindowIndex
                whenReady = playWhenReady
            }
            // Stop the player.
            stop()
        }
        info { "SimpleExoPlayer is released" }
    }
}