MainActivity.kt

class MainActivity : AppCompatActivity() {

    private var currentPlaybackState: MainActivityViewModel.VideoPlaybackState? = null
    private var currentLayoutState: MainActivityViewModel.VideoLayoutState? = null
    
    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        super.onCreateOptionsMenu(menu)
        menuInflater.inflate(R.menu.options_menu, menu)
        return true
    }

    override fun onPrepareOptionsMenu(menu: Menu?): Boolean {
        super.onPrepareOptionsMenu(menu)
        val playVideoItem = menu?.findItem(R.id.option_play_video)
        val stopVideoItem = menu?.findItem(R.id.option_stop_video)

        playVideoItem?.isVisible = currentPlaybackState == MainActivityViewModel.VideoPlaybackState.STOPPED
        stopVideoItem?.isVisible = currentPlaybackState == MainActivityViewModel.VideoPlaybackState.PLAYING

        return true
    }

    override fun onOptionsItemSelected(item: MenuItem?): Boolean {
        return when (item?.itemId) {
            R.id.option_play_video -> {
                viewModel.onVideoToggled()
                true
            }
            R.id.option_stop_video -> {
                viewModel.onVideoToggled()
                true
            }
            else -> super.onOptionsItemSelected(item)
        }
    }
}