Make PlaybackService persistent

Make PlaybackService solely rely on PlaybackStateManager, allowing the service to run beyond the main Auxio activity.

app/src/main/AndroidManifest.xml

@@ -26,7 +26,6 @@
         <service android:name=".playback.PlaybackService"
             android:icon="@drawable/ic_launcher_foreground"
             android:description="@string/description_service_playback"
-            android:stopWithTask="false"/>
+            android:stopWithTask="false" />
     </application>
-
 </manifest>

app/src/main/java/org/oxycblt/auxio/playback/PlaybackService.kt

@@ -1,10 +1,15 @@
 package org.oxycblt.auxio.playback
 
+import android.app.Notification
+import android.app.NotificationChannel
+import android.app.NotificationManager
 import android.app.Service
+import android.content.Context
 import android.content.Intent
-import android.os.Binder
 import android.os.Build
 import android.os.IBinder
+import android.util.Log
+import androidx.core.app.NotificationCompat
 import com.google.android.exoplayer2.MediaItem
 import com.google.android.exoplayer2.Player
 import com.google.android.exoplayer2.SimpleExoPlayer
@@ -17,11 +22,15 @@ import kotlinx.coroutines.flow.conflate
 import kotlinx.coroutines.flow.flow
 import kotlinx.coroutines.flow.takeWhile
 import kotlinx.coroutines.launch
+import org.oxycblt.auxio.R
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.music.toURI
 import org.oxycblt.auxio.playback.state.PlaybackStateCallback
 import org.oxycblt.auxio.playback.state.PlaybackStateManager
 
+private const val CHANNEL_ID = "CHANNEL_AUXIO_PLAYBACK"
+private const val NOTIF_ID = 0xA0A0
+
 // A Service that manages the single ExoPlayer instance and [attempts] to keep
 // persistence if the app closes.
 class PlaybackService : Service(), Player.EventListener, PlaybackStateCallback {
@@ -34,7 +43,6 @@ class PlaybackService : Service(), Player.EventListener, PlaybackStateCallback {
         p
     }
 
-    private val mBinder = LocalBinder()
     private val playbackManager = PlaybackStateManager.getInstance()
 
     private val serviceJob = Job()
@@ -42,13 +50,25 @@ class PlaybackService : Service(), Player.EventListener, PlaybackStateCallback {
         serviceJob + Dispatchers.Main
     )
 
-    override fun onBind(intent: Intent): IBinder {
-        return mBinder
+    private var isForeground = false
+
+    private lateinit var notification: Notification
+
+    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
+        Log.d(this::class.simpleName, "Service is active.")
+
+        return START_STICKY
+    }
+
+    override fun onBind(intent: Intent): IBinder? {
+        return null
     }
 
     override fun onCreate() {
         super.onCreate()
 
+        notification = createNotification()
+
         playbackManager.addCallback(this)
     }
 
@@ -58,6 +78,8 @@ class PlaybackService : Service(), Player.EventListener, PlaybackStateCallback {
         player.release()
         serviceJob.cancel()
         playbackManager.removeCallback(this)
+
+        stopForeground(true)
     }
 
     override fun onPlaybackStateChanged(state: Int) {
@@ -69,8 +91,14 @@ class PlaybackService : Service(), Player.EventListener, PlaybackStateCallback {
     }
 
     override fun onSongUpdate(song: Song?) {
-        song?.let { song ->
-            val item = MediaItem.fromUri(song.id.toURI())
+        song?.let {
+            if (!isForeground) {
+                startForeground(NOTIF_ID, notification)
+
+                isForeground = true
+            }
+
+            val item = MediaItem.fromUri(it.id.toURI())
             player.setMediaItem(item)
             player.prepare()
             player.play()
@@ -87,13 +115,13 @@ class PlaybackService : Service(), Player.EventListener, PlaybackStateCallback {
         }
     }
 
-    fun doSeek(position: Long) {
+    override fun onSeekConfirm(position: Long) {
         player.seekTo(position * 1000)
     }
 
     // Awful Hack to get position polling to work, as exoplayer does not provide any
     // onPositionChanged callback for some inane reason.
-    // FIXME: Consider using exoplayer UI elements here, don't be surprised if this causes problems.
+    // FIXME: Don't be surprised if this causes problems.
 
     private fun pollCurrentPosition() = flow {
         while (player.currentPosition <= player.duration) {
@@ -110,7 +138,29 @@ class PlaybackService : Service(), Player.EventListener, PlaybackStateCallback {
         }
     }
 
-    inner class LocalBinder : Binder() {
-        fun getService() = this@PlaybackService
+    private fun createNotification(): Notification {
+        val notificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            val channel = NotificationChannel(
+                CHANNEL_ID,
+                getString(R.string.description_playback),
+                NotificationManager.IMPORTANCE_DEFAULT
+            )
+            notificationManager.createNotificationChannel(channel)
+        }
+        // TODO: Placeholder, implement proper media controls :)
+        val notif = NotificationCompat.Builder(
+            applicationContext,
+            CHANNEL_ID
+        )
+            .setSmallIcon(R.drawable.ic_song)
+            .setContentTitle(getString(R.string.app_name))
+            .setContentText(getString(R.string.description_playback))
+            .setPriority(NotificationCompat.PRIORITY_DEFAULT)
+            .setChannelId(CHANNEL_ID)
+            .build()
+
+        return notif
     }
 }

app/src/main/java/org/oxycblt/auxio/playback/PlaybackViewModel.kt

@@ -1,10 +1,7 @@
 package org.oxycblt.auxio.playback
 
-import android.content.ComponentName
 import android.content.Context
 import android.content.Intent
-import android.content.ServiceConnection
-import android.os.IBinder
 import android.util.Log
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.MutableLiveData
@@ -68,25 +65,22 @@ class PlaybackViewModel(private val context: Context) : ViewModel(), PlaybackSta
     // Service setup
     private val playbackManager = PlaybackStateManager.getInstance()
 
-    private lateinit var playbackService: PlaybackService
-    private var playbackIntent: Intent
-
-    private val connection = object : ServiceConnection {
-        override fun onServiceConnected(name: ComponentName, binder: IBinder) {
-            playbackService = (binder as PlaybackService.LocalBinder).getService()
-        }
-
-        override fun onServiceDisconnected(name: ComponentName) {
-            Log.d(this::class.simpleName, "Service disconnected.")
-        }
-    }
-
     init {
-        playbackIntent = Intent(context, PlaybackService::class.java).also {
-            context.bindService(it, connection, Context.BIND_AUTO_CREATE)
+        // Start the service from the ViewModel.
+        // Yes, I know ViewModels aren't supposed to deal with this stuff but for some
+        // reason it only works here.
+        Intent(context, PlaybackService::class.java).also {
+            context.startService(it)
         }
 
         playbackManager.addCallback(this)
+
+        // If the PlaybackViewModel was cleared [signified by the PlaybackStateManager having a
+        // song and the fact that were are in the init function], then try to restore the playback
+        // state.
+        if (playbackManager.song != null) {
+            restorePlaybackState()
+        }
     }
 
     // --- PLAYING FUNCTIONS ---
@@ -143,11 +137,8 @@ class PlaybackViewModel(private val context: Context) : ViewModel(), PlaybackSta
     }
 
     // Update the position and push the change the playbackManager.
-    // This is done when the seek is confirmed to make playbackService seek to the position.
     fun updatePosition(progress: Int) {
-        playbackManager.setPosition(progress.toLong())
-
-        playbackService.doSeek(progress.toLong())
+        playbackManager.seekTo(progress.toLong())
     }
 
     // --- QUEUE FUNCTIONS ---
@@ -241,6 +232,15 @@ class PlaybackViewModel(private val context: Context) : ViewModel(), PlaybackSta
         mIsShuffling.value = isShuffling
     }
 
+    private fun restorePlaybackState() {
+        mSong.value = playbackManager.song
+        mPosition.value = playbackManager.position
+        mQueue.value = playbackManager.queue
+        mIndex.value = playbackManager.index
+        mIsPlaying.value = playbackManager.isPlaying
+        mIsShuffling.value = playbackManager.isShuffling
+    }
+
     class Factory(private val context: Context) : ViewModelProvider.Factory {
         @Suppress("unchecked_cast")
         override fun <T : ViewModel?> create(modelClass: Class<T>): T {

app/src/main/java/org/oxycblt/auxio/playback/state/PlaybackStateCallback.kt

@@ -9,4 +9,5 @@ interface PlaybackStateCallback {
     fun onPlayingUpdate(isPlaying: Boolean) {}
     fun onShuffleUpdate(isShuffling: Boolean) {}
     fun onIndexUpdate(index: Int) {}
+    fun onSeekConfirm(position: Long) {}
 }

app/src/main/java/org/oxycblt/auxio/playback/state/PlaybackStateManager.kt

@@ -52,6 +52,10 @@ class PlaybackStateManager {
         }
     private var mShuffleSeed = -1L
 
+    val song: Song? get() = mSong
+    val position: Long get() = mPosition
+    val queue: MutableList<Song> get() = mQueue
+    val index: Int get() = mIndex
     val isPlaying: Boolean get() = mIsPlaying
     val isShuffling: Boolean get() = mIsShuffling
 
@@ -164,6 +168,12 @@ class PlaybackStateManager {
         mPosition = position
     }
 
+    fun seekTo(position: Long) {
+        mPosition = position
+
+        callbacks.forEach { it.onSeekConfirm(position) }
+    }
+
     // --- QUEUE FUNCTIONS ---
 
     fun next() {

app/src/main/res/values/strings.xml

@@ -48,6 +48,8 @@
     <string name="description_shuffle_on">Turn shuffle on</string>
     <string name="description_shuffle_off">Turn shuffle off</string>
     <string name="description_service_playback">The music playback service for Auxio</string>
+    <string name="description_notif_playback">Music Playback</string>
+    <string name="description_playback">Auxio is playing music</string>
 
     <!-- Placeholder Namespace | Placeholder values -->
     <string name="placeholder_genre">Unknown Genre</string>