PlayerActivity.kt

    private fun initializePlayer() {
        if (player == null) {
            player = ExoPlayerFactory.newSimpleInstance(
                    DefaultRenderersFactory(context),
                    DefaultTrackSelector(),
                    DefaultLoadControl())
            playerView?.setPlayer(player)
            player.setPlayWhenReady(playWhenReady)
            player.seekTo(currentWindow, playbackPosition)
        }
        val mediaSource = buildMediaSource(Uri.parse(getString(R.string.media_url_mp4)))
        player.prepare(mediaSource, true, false)
    }

    private fun buildMediaSource(uri: Uri): MediaSource {

        val userAgent = "exoplayer-codelab"

        if (uri.getLastPathSegment().contains("mp3") || uri.getLastPathSegment().contains("mp4")) {
            return ExtractorMediaSource.Factory(DefaultHttpDataSourceFactory(userAgent))
                    .createMediaSource(uri)
        } else if (uri.getLastPathSegment().contains("m3u8")) {
            return HlsMediaSource.Factory(DefaultHttpDataSourceFactory(userAgent))
                    .createMediaSource(uri)
        } else {
            val dashChunkSourceFactory = DefaultDashChunkSource.Factory(
                    DefaultHttpDataSourceFactory("ua", BANDWIDTH_METER))
            val manifestDataSourceFactory = DefaultHttpDataSourceFactory(userAgent)
            return DashMediaSource.Factory(dashChunkSourceFactory, manifestDataSourceFactory).createMediaSource(uri)
        }
    }

    private fun releasePlayer() {
        if (player != null) {
            playbackPosition = player.getCurrentPosition()
            currentWindow = player.getCurrentWindowIndex()
            playWhenReady = player.getPlayWhenReady()
            player.release()
            player = null
        }
    }