Android Kotlin 音声をバックグラウンドで出力し、音声の終了時に通知を表示したい。

参考書に従い、音声をバックグラウンドで出力し、音声の終了時に通知を表示したいのですが
通知がされません。

見直したものの参考書との差異はないように思います。
間違っている箇所がありましたら、ご指摘をお願いいたします。

xml
1<?xml version="1.0" encoding="utf-8"?>
2<LinearLayout
3    xmlns:android="http://schemas.android.com/apk/res/android"
4    android:layout_width="match_parent"
5    android:layout_height="match_parent"
6    android:orientation="vertical">
7
8    <Button
9        android:id="@+id/btPlay"
10        android:layout_width="match_parent"
11        android:layout_height="wrap_content"
12        android:onClick="onPlayButtonClick"
13        android:text="@string/bt_play_play"/>
14
15    <Button
16        android:id="@+id/btStop"
17        android:layout_width="match_parent"
18        android:layout_height="wrap_content"
19        android:enabled="false"
20        android:onClick="onStopButtonClick"
21        android:text="@string/bt_play_stop"/>
22
23
24</LinearLayout>

xml
1<?xml version="1.0" encoding="utf-8"?>
2<manifest xmlns:android="http://schemas.android.com/apk/res/android"
3    package="com.websarva.wings.android.servicesample">
4
5    <application
6        android:allowBackup="true"
7        android:icon="@mipmap/ic_launcher"
8        android:label="@string/app_name"
9        android:roundIcon="@mipmap/ic_launcher_round"
10        android:supportsRtl="true"
11        android:theme="@style/AppTheme">
12        <service
13            android:name=".SoundManagerService"
14            android:enabled="true"
15            android:exported="false"></service>
16
17        <activity android:name=".MainActivity">
18            <intent-filter>
19                <action android:name="android.intent.action.MAIN" />
20
21                <category android:name="android.intent.category.LAUNCHER" />
22            </intent-filter>
23        </activity>
24    </application>
25
26</manifest>

kotlin
1package com.websarva.wings.android.servicesample
2
3import android.content.Intent
4import android.support.v7.app.AppCompatActivity
5import android.os.Bundle
6import android.view.View
7import android.widget.Button
8
9class MainActivity : AppCompatActivity() {
10
11    override fun onCreate(savedInstanceState: Bundle?) {
12        super.onCreate(savedInstanceState)
13        setContentView(R.layout.activity_main)
14    }
15
16    fun onPlayButtonClick(view: View) {
17        val intent = Intent(applicationContext, SoundManagerService::class.java)
18        startService(intent)
19
20        val btPlay = findViewById<Button>(R.id.btPlay)
21        val btStop = findViewById<Button>(R.id.btStop)
22
23        btPlay.isEnabled = false
24        btStop.isEnabled = true
25    }
26
27    fun onStopButtonClick(view: View) {
28        val intent = Intent(applicationContext, SoundManagerService::class.java)
29        stopService(intent)
30
31        val btPlay = findViewById<Button>(R.id.btPlay)
32        val btStop = findViewById<Button>(R.id.btStop)
33
34        btPlay.isEnabled = true
35        btStop.isEnabled = false
36    }
37}
38

kotlin
1package com.websarva.wings.android.servicesample
2
3import android.app.NotificationChannel
4import android.app.NotificationManager
5import android.app.Service
6import android.content.Context
7import android.content.Intent
8import android.media.MediaPlayer
9import android.net.Uri
10import android.os.IBinder
11import android.support.v4.app.NotificationCompat
12import android.util.Log
13import android.view.View
14import java.io.IOException
15import java.lang.IllegalArgumentException
16
17class SoundManagerService : Service() {
18
19    override fun onBind(intent: Intent): IBinder {
20        TODO("Return the communication channel to the service.")
21    }
22
23    private var _player: MediaPlayer? = null
24    override fun onCreate() {
25        _player = MediaPlayer()
26
27        val id = "soundmanagerservice_notification_channel"
28        val name = getString(R.string.notification_channel_name)
29        val importance = NotificationManager.IMPORTANCE_DEFAULT
30        val channel = NotificationChannel(id, name, importance)
31
32        val manager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
33        manager.createNotificationChannel(channel)
34    }
35
36    override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {
37
38        val mediaFileUriStr = "android.resource://${packageName}/${R.raw.mountain_stream}"
39        val mediaFileUri = Uri.parse(mediaFileUriStr)
40
41        try {
42            _player?.setDataSource(applicationContext, mediaFileUri)
43            _player?.setOnPreparedListener(PlayerPreparedListener())
44            _player?.setOnCompletionListener(PlayerCompletionListener())
45            _player?.prepareAsync()
46        } catch (ex: IllegalArgumentException) {
47            Log.e("ServiceSample", "メディアプレーヤー準備時の例外発生")
48        } catch (ex: IOException) {
49            Log.e("ServiceSample", "メディアプレーヤー準備時の例外発生")
50        }
51
52        return Service.START_NOT_STICKY
53    }
54
55    override fun onDestroy() {
56
57        _player?.let {
58            if (it.isPlaying) {
59                it.stop()
60            }
61
62            it.release()
63            _player = null
64        }
65    }
66
67    private inner class PlayerPreparedListener : MediaPlayer.OnPreparedListener {
68        override fun onPrepared(mp: MediaPlayer) {
69            mp.start()
70        }
71    }
72
73    private inner class PlayerCompletionListener : MediaPlayer.OnCompletionListener {
74        override fun onCompletion(mp: MediaPlayer) {
75            val builder = NotificationCompat.Builder(applicationContext, "soundmanagerservice_notification_channel")
76            builder.setSmallIcon(android.R.drawable.ic_dialog_info)
77            builder.setContentTitle(getString(R.string.msg_notification_title_finish))
78            builder.setContentText(getString(R.string.msg_notification_text_finish))
79
80            val notification = builder.build()
81            val manager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
82            manager.notify(0, notification)
83
84            stopSelf()
85        }
86    }
87
88
89}
90