VolumeKeyHandler: Add support for skipping tracks with remote control

For Spotify and other players that allow music controls for
remote devices (PC, PS4) through the media notification

Change-Id: I38887f8b1cff1a0c1e3adadbfe37d5af59b5cdcc

core/java/com/android/internal/util/libremobileos/VolumeKeyHandler.java

 /**
- * Copyright (C) 2017 The LineageOS Project
+ * Copyright (C) 2018,2020 The LineageOS Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,7 +21,10 @@ import android.content.Context;
 import android.content.res.Resources;
 import android.database.ContentObserver;
 import android.media.AudioManager;
+import android.media.session.MediaController;
 import android.media.session.MediaSessionLegacyHelper;
+import android.media.session.MediaSessionManager;
+import android.media.session.PlaybackState;
 import android.os.Handler;
 import android.os.Message;
 import android.os.UserHandle;
@@ -30,6 +33,8 @@ import android.util.Slog;
 import android.view.KeyEvent;
 import android.view.ViewConfiguration;
 
+import java.util.List;
+
 public final class VolumeKeyHandler {
     private final String TAG = "VolumeKeyHandler";
     private final boolean DEBUG = false;
@@ -37,7 +42,8 @@ public final class VolumeKeyHandler {
     private static final int MSG_DISPATCH_VOLKEY_WITH_WAKELOCK = 1;
 
     private final Context mContext;
-    private ButtonHandler mHandler;
+    private final ButtonHandler mHandler;
+    private final MediaSessionManager mMediaSessionManager;
 
     private boolean mIsLongPress = false;
 
@@ -53,8 +59,7 @@ public final class VolumeKeyHandler {
                     if (DEBUG) {
                         Slog.d(TAG, "Dispatching key to audio service");
                     }
-                    dispatchMediaKeyToAudioService(ev);
-                    dispatchMediaKeyToAudioService(KeyEvent.changeAction(ev, KeyEvent.ACTION_UP));
+                    onSkipTrackEvent(ev);
                     break;
             }
         }
@@ -63,6 +68,7 @@ public final class VolumeKeyHandler {
     public VolumeKeyHandler(Context context) {
         mContext = context;
         mHandler = new ButtonHandler();
+        mMediaSessionManager = mContext.getSystemService(MediaSessionManager.class);
 
         SettingsObserver observer = new SettingsObserver(new Handler());
         observer.observe();
@@ -128,11 +134,34 @@ public final class VolumeKeyHandler {
         return true;
     }
 
-    void dispatchMediaKeyToAudioService(KeyEvent ev) {
-        if (DEBUG) {
-            Slog.d(TAG, "Dispatching KeyEvent " + ev + " to audio service");
+    private void triggerKeyEvents(KeyEvent evDown, MediaController controller) {
+        final KeyEvent evUp = KeyEvent.changeAction(evDown, KeyEvent.ACTION_UP);
+        mHandler.post(() -> controller.dispatchMediaButtonEvent(evDown));
+        mHandler.postDelayed(() -> controller.dispatchMediaButtonEvent(evUp), 20);
+    }
+
+    public void onSkipTrackEvent(KeyEvent ev) {
+        if (mMediaSessionManager != null) {
+            final List<MediaController> sessions = mMediaSessionManager.getActiveSessionsForUser(
+                    null, UserHandle.USER_ALL);
+            for (MediaController mediaController : sessions) {
+                if (PlaybackState.STATE_PLAYING ==
+                        getMediaControllerPlaybackState(mediaController)) {
+                    triggerKeyEvents(ev, mediaController);
+                    break;
+                }
+            }
+        }
+    }
+
+    private int getMediaControllerPlaybackState(MediaController controller) {
+        if (controller != null) {
+            final PlaybackState playbackState = controller.getPlaybackState();
+            if (playbackState != null) {
+                return playbackState.getState();
+            }
         }
-        MediaSessionLegacyHelper.getHelper(mContext).sendMediaButtonEvent(ev, true);
+        return PlaybackState.STATE_NONE;
     }
 
     class SettingsObserver extends ContentObserver {