From 4f55a2a4a5441c458e4a14720ba0ca6bc2e83f30 Mon Sep 17 00:00:00 2001
From: birdbird <6892457-tzugen@users.noreply.gitlab.com>
Date: Mon, 24 Jul 2023 18:57:29 +0000
Subject: [PATCH] Fix an exception when removeIncompleteTracksFromPlaylist()
 could be called on the wrong thread.

---
 .../ultrasonic/service/MediaPlayerManager.kt  | 43 ++++++++++---------
 .../org/moire/ultrasonic/service/RxBus.kt     |  9 +---
 2 files changed, 25 insertions(+), 27 deletions(-)

diff --git a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/service/MediaPlayerManager.kt b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/service/MediaPlayerManager.kt
index d1ffd067..2a4cbbdc 100644
--- a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/service/MediaPlayerManager.kt
+++ b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/service/MediaPlayerManager.kt
@@ -181,19 +181,22 @@ class MediaPlayerManager(
 
         createMediaController(onCreated)
 
-        rxBusSubscription += RxBus.activeServerChangingObservable.subscribe { oldServer ->
-            if (oldServer != OFFLINE_DB_ID) {
-                // When the server changes, the playlist can retain the downloaded songs.
-                // Incomplete songs should be removed as the new server won't recognise them.
-                removeIncompleteTracksFromPlaylist()
-                DownloadService.requestStop()
+        rxBusSubscription += RxBus.activeServerChangingObservable
+            // All interaction with the Media3 needs to happen on the main thread
+            .subscribeOn(RxBus.mainThread())
+            .subscribe { oldServer ->
+                if (oldServer != OFFLINE_DB_ID) {
+                    // When the server changes, the playlist can retain the downloaded songs.
+                    // Incomplete songs should be removed as the new server won't recognise them.
+                    removeIncompleteTracksFromPlaylist()
+                    DownloadService.requestStop()
+                }
+                if (controller is JukeboxMediaPlayer) {
+                    // When the server changes, the Jukebox should be released.
+                    // The new server won't understand the jukebox requests of the old one.
+                    switchToLocalPlayer()
+                }
             }
-            if (controller is JukeboxMediaPlayer) {
-                // When the server changes, the Jukebox should be released.
-                // The new server won't understand the jukebox requests of the old one.
-                switchToLocalPlayer()
-            }
-        }
 
         rxBusSubscription += RxBus.activeServerChangedObservable.subscribe {
             val jukebox = activeServerProvider.getActiveServer().jukeboxByDefault
@@ -204,19 +207,19 @@ class MediaPlayerManager(
             isJukeboxEnabled = jukebox
         }
 
-        rxBusSubscription += RxBus.throttledPlaylistObservable.subscribe {
-            // Even though Rx should launch on the main thread it doesn't always :(
-            mainScope.launch {
+        rxBusSubscription += RxBus.throttledPlaylistObservable
+            // All interaction with the Media3 needs to happen on the main thread
+            .subscribeOn(RxBus.mainThread())
+            .subscribe {
                 serializeCurrentSession()
             }
-        }
 
-        rxBusSubscription += RxBus.throttledPlayerStateObservable.subscribe {
-            // Even though Rx should launch on the main thread it doesn't always :(
-            mainScope.launch {
+        rxBusSubscription += RxBus.throttledPlayerStateObservable
+            // All interaction with the Media3 needs to happen on the main thread
+            .subscribeOn(RxBus.mainThread())
+            .subscribe {
                 serializeCurrentSession()
             }
-        }
 
         rxBusSubscription += RxBus.shutdownCommandObservable.subscribe {
             clear(false)
diff --git a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/service/RxBus.kt b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/service/RxBus.kt
index 9c87c519..9912cf0d 100644
--- a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/service/RxBus.kt
+++ b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/service/RxBus.kt
@@ -1,8 +1,8 @@
 package org.moire.ultrasonic.service
 
-import android.os.Looper
 import io.reactivex.rxjava3.android.schedulers.AndroidSchedulers
 import io.reactivex.rxjava3.core.Observable
+import io.reactivex.rxjava3.core.Scheduler
 import io.reactivex.rxjava3.disposables.CompositeDisposable
 import io.reactivex.rxjava3.disposables.Disposable
 import io.reactivex.rxjava3.subjects.PublishSubject
@@ -12,14 +12,9 @@ import org.moire.ultrasonic.domain.Track
 
 class RxBus {
 
-    /*
-    * TODO: mainThread() seems to be not equal to the "normal" main Thread, so it causes
-    * a lot of often unnecessary thread switching. It looks like observeOn can actually
-    * be removed in many cases
-    */
     companion object {
 
-        private fun mainThread() = AndroidSchedulers.from(Looper.getMainLooper())
+        fun mainThread(): Scheduler = AndroidSchedulers.mainThread()
 
         val shufflePlayPublisher: PublishSubject<Boolean> =
             PublishSubject.create()