android: Support play / pause from media session

android/app/src/main/java/org/musicpd/Bridge.java

@@ -18,6 +18,7 @@ public class Bridge {
 	public static native void run(Context context, LogListener logListener);
 	public static native void shutdown();
 	public static native void pause();
+	public static native void playPause();
 	public static native void playNext();
 	public static native void playPrevious();
 }

android/app/src/main/java/org/musicpd/MPDPlayer.java

@@ -36,7 +36,11 @@ public class MPDPlayer extends SimpleBasePlayer {
     @NonNull
     @Override
     protected State getState() {
-        Commands commands = new Commands.Builder().addAll(COMMAND_SEEK_TO_PREVIOUS_MEDIA_ITEM, COMMAND_SEEK_TO_NEXT_MEDIA_ITEM).build();
+        Commands commands = new Commands.Builder().addAll(
+                COMMAND_SEEK_TO_PREVIOUS_MEDIA_ITEM,
+                COMMAND_SEEK_TO_NEXT_MEDIA_ITEM,
+                COMMAND_PLAY_PAUSE
+        ).build();
 
         return new State.Builder()
                 .setAvailableCommands(commands)
@@ -46,6 +50,13 @@ public class MPDPlayer extends SimpleBasePlayer {
                 .build();
     }
 
+    @NonNull
+    @Override
+    protected ListenableFuture<?> handleSetPlayWhenReady(boolean playWhenReady) {
+        Bridge.playPause();
+        return Futures.immediateVoidFuture();
+    }
+
     @NonNull
     @SuppressLint("SwitchIntDef")
     @Override

src/Main.cxx

@@ -614,6 +614,16 @@ Java_org_musicpd_Bridge_pause(JNIEnv *, jclass)
 			partition.pc.LockSetPause(true);
 }
 
+gcc_visibility_default
+JNIEXPORT void JNICALL
+Java_org_musicpd_Bridge_playPause(JNIEnv *, jclass)
+{
+	if (global_instance != nullptr)
+		for (auto &partition : global_instance->partitions)
+			partition.pc.LockPause();
+
+}
+
 gcc_visibility_default
 JNIEXPORT void JNICALL
 Java_org_musicpd_Bridge_playNext(JNIEnv *, jclass)