playback: fix gadgetbridge regression [#62]

Fix a regression where media button controls would no longer work
with GadgetBridge.

In 4a79de4, I assumed that my code was redundant, as there should be
some kind of reciever handling media button events already. I was
completely wrong. Re-add the reciever code (with extra checks) to
make controls work again.

app/build.gradle

@@ -75,7 +75,6 @@ dependencies {
     implementation "androidx.lifecycle:lifecycle-common:$lifecycle_version"
     implementation "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version"
     implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version"
-    implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
     implementation "androidx.lifecycle:lifecycle-runtime-ktx:$lifecycle_version"
 
     // Navigation

app/src/main/java/org/oxycblt/auxio/playback/system/MediaButtonReceiver.kt

@@ -18,8 +18,11 @@
 package org.oxycblt.auxio.playback.system
 
 import android.content.BroadcastReceiver
+import android.content.ComponentName
 import android.content.Context
 import android.content.Intent
+import androidx.core.content.ContextCompat
+import org.oxycblt.auxio.playback.state.PlaybackStateManager
 
 /**
  * Some apps like to party like it's 2011 and just blindly query for the ACTION_MEDIA_BUTTON intent
@@ -27,9 +30,16 @@ import android.content.Intent
  * MediaSession that an app should control instead through the much better MediaController API. But
  * who cares about that, we need to make sure the 3% of barely functioning TouchWiz devices running
  * KitKat don't break! To prevent Auxio from not showing up at all in these apps, we declare a
- * BroadcastReceiver in the manifest that actually does nothing. Any broadcast by apps should be
- * routed by the media session when the service exists.
+ * BroadcastReceiver in the manifest that hacks in this functionality.
  */
 class MediaButtonReceiver : BroadcastReceiver() {
-    override fun onReceive(context: Context, intent: Intent) {}
+    override fun onReceive(context: Context, intent: Intent) {
+        val playbackManager = PlaybackStateManager.getInstance()
+        if (playbackManager.song != null) {
+            // We have a song, so we can assume that the service will start a foreground state.
+            // At least, I hope
+            intent.component = ComponentName(context, PlaybackService::class.java)
+            ContextCompat.startForegroundService(context, intent)
+        }
+    }
 }

app/src/main/java/org/oxycblt/auxio/playback/system/MediaSessionComponent.kt

@@ -24,6 +24,7 @@ import android.os.SystemClock
 import android.support.v4.media.MediaMetadataCompat
 import android.support.v4.media.session.MediaSessionCompat
 import android.support.v4.media.session.PlaybackStateCompat
+import androidx.media.session.MediaButtonReceiver
 import com.google.android.exoplayer2.Player
 import org.oxycblt.auxio.image.BitmapProvider
 import org.oxycblt.auxio.music.MusicParent
@@ -57,6 +58,10 @@ class MediaSessionComponent(private val context: Context, private val player: Pl
         mediaSession.setCallback(this)
     }
 
+    fun handleMediaButtonIntent(intent: Intent) {
+        MediaButtonReceiver.handleIntent(mediaSession, intent)
+    }
+
     fun release() {
         provider.release()
         player.removeListener(this)

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

@@ -147,7 +147,13 @@ class PlaybackService :
         logD("Service created")
     }
 
-    override fun onStartCommand(intent: Intent, flags: Int, startId: Int) = START_NOT_STICKY
+    override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {
+        if (intent.action == Intent.ACTION_MEDIA_BUTTON) {
+            mediaSessionComponent.handleMediaButtonIntent(intent)
+        }
+
+        return START_NOT_STICKY
+    }
 
     // No binding, service is headless
     // Communicate using PlaybackStateManager, SettingsManager, or Broadcasts instead.