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    private fun extractMediaSourceFromUri(uri: Uri): MediaSource {
        val userAgent = Util.getUserAgent(this, "Exo")
        return ExtractorMediaSource.Factory(DefaultDataSourceFactory(this, userAgent))
            .setExtractorsFactory(DefaultExtractorsFactory()).createMediaSource(uri)
    }

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   override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_player)
        val mediaSource = extractMediaSourceFromUri(Uri.parse("asset:///heart_attack.mp3"))
        val exoPlayer = ExoPlayerFactory.newSimpleInstance(
            baseContext, DefaultRenderersFactory(baseContext)
            , DefaultTrackSelector(),
            DefaultLoadControl()
        )
        exoPlayer.apply {

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class MusicService : MediaBrowserServiceCompat() {
    
    override fun onLoadChildren(parentId: String, result: Result<MutableList<MediaBrowserCompat.MediaItem>>) {
    
    }

    override fun onGetRoot(clientPackageName: String, clientUid: Int, rootHints: Bundle?): BrowserRoot? {
        return BrowserRoot("", null)
    }
}

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        <service android:name=".MusicService">
            <intent-filter>
                <action android:name="android.media.browse.MediaBrowserService"/>
            </intent-filter>
        </service>

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class MusicService : MediaBrowserServiceCompat() {
    private var mMediaSession: MediaSessionCompat? = null
    private lateinit var mStateBuilder: PlaybackStateCompat.Builder
    private var mExoPlayer: SimpleExoPlayer? = null
    private var oldUri: Uri? = null
    private val mMediaSessionCallback = object : MediaSessionCompat.Callback() {
        override fun onPlayFromUri(uri: Uri?, extras: Bundle?) {
            super.onPlayFromUri(uri, extras)
            uri?.let {
                val mediaSource = extractMediaSourceFromUri(uri)

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class PlayerActivity : AppCompatActivity() {

    private lateinit var mMediaBrowserCompat: MediaBrowserCompat
    private val connectionCallback: MediaBrowserCompat.ConnectionCallback = object : MediaBrowserCompat.ConnectionCallback() {
        override fun onConnected() {

            // The browser connected to the session successfully, use the token to create the controller
            super.onConnected()
            mMediaBrowserCompat.sessionToken.also { token ->

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interface Displayable {
    fun getType(): Int
}
// ----------------------------------
abstract class ViewRenderer<in D : Displayable, VH : RecyclerView.ViewHolder>(val type: Int) {
    abstract fun bindView(model: D, holder: VH)
    abstract fun createViewHolder(parent: ViewGroup): VH
}

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// Those are two tasks. 

// TASK 1 
open class SingletonHolder<out T, in A>(creator: (A) -> T) {

    private var creator: ((A) -> T)? = creator

    @Volatile
    private var instance: T? = null

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// With the assumption, this code is written inside a view
// choose a reasonable range of colors, some ranges won't be drawn and I don't know why actually.
private val shadowStartColor = 0x99ffffff.toInt()
private val shadowEndColor = 0x03ffffff
private val shadowSize = 50f
val radialGradientPaint =RadialGradient(centerX
, centerY,
radius,
intArrayOf(shadowStartColor, shadowEndColor),
floatArrayOf(0f,  1f),

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val path = Path()
        val paint = Paint()


        paint.apply {
            strokeWidth = 20f
            style = Paint.Style.STROKE
        }
        path.apply {
            moveTo(xCenter, yCenter)