clean up playback interface and a few other classes

app/src/main/java/com/dkanada/gramophone/service/MultiPlayer.java

@@ -46,7 +46,6 @@ public class MultiPlayer implements Playback {
     private boolean isReady = false;
     private boolean isPlaying = false;
     private boolean isNew = false;
-    private boolean isFirst = true;
 
     private ExoPlayer.EventListener eventListener = new ExoPlayer.EventListener() {
         @Override
@@ -118,7 +117,7 @@ public class MultiPlayer implements Playback {
     }
 
     @Override
-    public void setNextDataSource(@Nullable final String path) {
+    public void queueDataSource(@Nullable final String path) {
         if (context == null) {
             return;
         }
@@ -151,11 +150,7 @@ public class MultiPlayer implements Playback {
                 }
 
                 mediaSource.addMediaSource(source);
-                if (!isFirst && next) {
-                    start();
-                }
-
-                isFirst = false;
+                if (next) start();
             }
         });
     }
@@ -171,7 +166,7 @@ public class MultiPlayer implements Playback {
     }
 
     @Override
-    public boolean start() {
+    public void start() {
         isPlaying = true;
         exoPlayer.setPlayWhenReady(true);
 
@@ -179,8 +174,6 @@ public class MultiPlayer implements Playback {
             callbacks.onTrackStarted();
             isNew = false;
         }
-
-        return true;
     }
 
     @Override
@@ -190,10 +183,9 @@ public class MultiPlayer implements Playback {
     }
 
     @Override
-    public boolean pause() {
+    public void pause() {
         isPlaying = false;
         exoPlayer.setPlayWhenReady(false);
-        return true;
     }
 
     @Override
@@ -220,8 +212,7 @@ public class MultiPlayer implements Playback {
     }
 
     @Override
-    public boolean setVolume(float volume) {
+    public void setVolume(float volume) {
         exoPlayer.setVolume(volume);
-        return true;
     }
 }

app/src/main/java/com/dkanada/gramophone/service/MusicService.java

@@ -218,6 +218,7 @@ public class MusicService extends Service implements SharedPreferences.OnSharedP
         if (audioManager == null) {
             audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
         }
+
         return audioManager;
     }
 
@@ -422,7 +423,7 @@ public class MusicService extends Service implements SharedPreferences.OnSharedP
                 this.playingQueue = restoredQueue;
 
                 position = restoredPosition;
-                openCurrent();
+                openCurrent(true);
 
                 if (restoredPositionInTrack > 0) seek(restoredPositionInTrack);
 
@@ -471,18 +472,25 @@ public class MusicService extends Service implements SharedPreferences.OnSharedP
         synchronized (this) {
             this.position = position;
 
-            openCurrent();
+            openCurrent(false);
 
             notifyChange(META_CHANGED);
             notHandledMetaChangedForCurrentTrack = false;
         }
     }
 
-    private void openCurrent() {
+    private void openCurrent(boolean queue) {
         synchronized (this) {
             // current song will be null when queue is cleared
             if (getCurrentSong() == null) return;
-            playback.setDataSource(getTrackUri(getCurrentSong()));
+
+            if (queue) {
+                // restore queue from database
+                playback.queueDataSource(getTrackUri(getCurrentSong()));
+            } else {
+                // set current song and start playback
+                playback.setDataSource(getTrackUri(getCurrentSong()));
+            }
         }
     }
 
@@ -494,7 +502,7 @@ public class MusicService extends Service implements SharedPreferences.OnSharedP
     private void prepareNextImpl() {
         synchronized (this) {
             nextPosition = getNextPosition(false);
-            playback.setNextDataSource(getTrackUri(getSongAt(nextPosition)));
+            playback.queueDataSource(getTrackUri(getSongAt(nextPosition)));
         }
     }
 

app/src/main/java/com/dkanada/gramophone/service/playback/Playback.java

@@ -1,31 +1,29 @@
 package com.dkanada.gramophone.service.playback;
 
-import androidx.annotation.Nullable;
-
 public interface Playback {
     void setDataSource(String path);
 
-    void setNextDataSource(@Nullable String path);
+    void queueDataSource(String path);
 
     void setCallbacks(PlaybackCallbacks callbacks);
 
-    boolean isInitialized();
+    void start();
 
-    boolean start();
+    void pause();
 
     void stop();
 
-    boolean pause();
+    boolean isInitialized();
 
     boolean isPlaying();
 
-    int duration();
-
     int position();
 
-    int seek(int whereto);
+    int duration();
 
-    boolean setVolume(float vol);
+    int seek(int position);
+
+    void setVolume(float volume);
 
     interface PlaybackCallbacks {
         void onTrackStarted();