PickingSoundsPlayer.kt

import android.content.Context
import android.media.MediaPlayer
import com.your.namespace.R
import kotlinx.coroutines.experimental.launch
import java.util.concurrent.atomic.AtomicLong
import javax.inject.Inject
import javax.inject.Singleton

/**
 * Plays picking noises.
 */
@Singleton
class PickingSoundsPlayer @Inject constructor(private val context: Context) {
    /** Need to keep a reference to the MediaPlayer or else GC sometimes kills it, cutting off any playing sound */
    private val mediaPlayers = mutableMapOf<Long, MediaPlayer>()
    private val counter = AtomicLong()

    private val sounds = mapOf(
        Sound.PickedItem to R.raw.sound_pick_partial,
        Sound.FinishedPickingItem to R.raw.sound_pick_full,
        Sound.PickingError to R.raw.sound_pick_error
    )

    fun play(sound: Sound) {
        val soundId = sounds[sound] ?: throw NullPointerException("Sound $sound doesn't exist!")
        val playerIndex = counter.incrementAndGet()

        launch {
            val mediaPlayer = MediaPlayer.create(context, soundId)
            mediaPlayers[playerIndex] = mediaPlayer
            mediaPlayer.setOnCompletionListener {
                mediaPlayer.release()
                mediaPlayers.remove(playerIndex)
            }

            mediaPlayer.start()
        }
    }

    sealed class Sound {
        object PickedItem : Sound()
        object FinishedPickingItem : Sound()
        object PickingError : Sound()
    }
}