Allow privileged app to set media key event listener

If the media key listener is set, the listener will receive the media key
events before any other sessions, but after the global priority session.
If the event is handled by the listener, other sessions cannot get the event.

Privileged app needs permission android.permission.SET_MEDIA_KEY_LISTENER
to set the listener.

Bug: 30125811
Change-Id: I2b2cf4ac7873b70899194701c6921990dcb9de02
diff --git a/services/core/java/com/android/server/media/MediaSessionService.java b/services/core/java/com/android/server/media/MediaSessionService.java
index 04d5d9f..3bf95ef 100644
--- a/services/core/java/com/android/server/media/MediaSessionService.java
+++ b/services/core/java/com/android/server/media/MediaSessionService.java
@@ -37,11 +37,13 @@
 import android.media.IAudioService;
 import android.media.IRemoteVolumeController;
 import android.media.session.IActiveSessionsListener;
+import android.media.session.IOnMediaKeyListener;
 import android.media.session.IOnVolumeKeyLongPressListener;
 import android.media.session.ISession;
 import android.media.session.ISessionCallback;
 import android.media.session.ISessionManager;
 import android.media.session.MediaSession;
+import android.media.session.MediaSessionManager;
 import android.net.Uri;
 import android.os.Binder;
 import android.os.Bundle;
@@ -84,6 +86,7 @@
     private static final boolean DEBUG_KEY_EVENT = true;
 
     private static final int WAKELOCK_TIMEOUT = 5000;
+    private static final int MEDIA_KEY_LISTENER_TIMEOUT = 1000;
 
     /* package */final IBinder mICallback = new Binder();
 
@@ -550,6 +553,9 @@
         private int mInitialDownVolumeStream;
         private boolean mInitialDownMusicOnly;
 
+        private IOnMediaKeyListener mOnMediaKeyListener;
+        private int mOnMediaKeyListenerUid;
+
         public UserRecord(Context context, int userId) {
             mContext = context;
             mUserId = userId;
@@ -583,6 +589,9 @@
             pw.println(indent + "Volume key long-press listener:" + mOnVolumeKeyLongPressListener);
             pw.println(indent + "Volume key long-press listener package:" +
                     getCallingPackageName(mOnVolumeKeyLongPressListenerUid));
+            pw.println(indent + "Media key listener: " + mOnMediaKeyListener);
+            pw.println(indent + "Media key listener package: " +
+                    getCallingPackageName(mOnMediaKeyListenerUid));
             int size = mSessions.size();
             pw.println(indent + size + " Sessions:");
             for (int i = 0; i < size; i++) {
@@ -788,28 +797,10 @@
                 }
 
                 synchronized (mLock) {
-                    // If we don't have a media button receiver to fall back on
-                    // include non-playing sessions for dispatching
-                    boolean useNotPlayingSessions = true;
-                    for (int userId : mCurrentUserIdList) {
-                        UserRecord ur = mUserRecords.get(userId);
-                        if (ur.mLastMediaButtonReceiver != null
-                                || ur.mRestoredMediaButtonReceiver != null) {
-                            useNotPlayingSessions = false;
-                            break;
-                        }
-                    }
-
-                    if (DEBUG) {
-                        Log.d(TAG, "dispatchMediaKeyEvent, useNotPlayingSessions="
-                                + useNotPlayingSessions);
-                    }
-                    MediaSessionRecord session = mPriorityStack.getDefaultMediaButtonSession(
-                            mCurrentUserIdList, useNotPlayingSessions);
-                    if (isVoiceKey(keyEvent.getKeyCode())) {
-                        handleVoiceKeyEventLocked(keyEvent, needWakeLock, session);
+                    if (!isGlobalPriorityActive() && isVoiceKey(keyEvent.getKeyCode())) {
+                        handleVoiceKeyEventLocked(keyEvent, needWakeLock);
                     } else {
-                        dispatchMediaKeyEventLocked(keyEvent, needWakeLock, session);
+                        dispatchMediaKeyEventLocked(keyEvent, needWakeLock, true);
                     }
                 }
             } finally {
@@ -868,6 +859,56 @@
             }
         }
 
+        @Override
+        public void setOnMediaKeyListener(IOnMediaKeyListener listener) {
+            final int pid = Binder.getCallingPid();
+            final int uid = Binder.getCallingUid();
+            final long token = Binder.clearCallingIdentity();
+            try {
+                // Enforce SET_MEDIA_KEY_LISTENER permission.
+                if (getContext().checkPermission(
+                        android.Manifest.permission.SET_MEDIA_KEY_LISTENER, pid, uid)
+                            != PackageManager.PERMISSION_GRANTED) {
+                    throw new SecurityException("Must hold the SET_MEDIA_KEY_LISTENER" +
+                            " permission.");
+                }
+
+                synchronized (mLock) {
+                    int userId = UserHandle.getUserId(uid);
+                    UserRecord user = mUserRecords.get(userId);
+                    if (user.mOnMediaKeyListener != null && user.mOnMediaKeyListenerUid != uid) {
+                        Log.w(TAG, "Media key listener cannot be reset by another app");
+                        return;
+                    }
+
+                    user.mOnMediaKeyListener = listener;
+                    user.mOnMediaKeyListenerUid = uid;
+
+                    Log.d(TAG, "Media key listener " + user.mOnMediaKeyListener
+                            + " is set by " + getCallingPackageName(uid));
+
+                    if (user.mOnMediaKeyListener != null) {
+                        try {
+                            user.mOnMediaKeyListener.asBinder().linkToDeath(
+                                    new IBinder.DeathRecipient() {
+                                        @Override
+                                        public void binderDied() {
+                                            synchronized (mLock) {
+                                                user.mOnMediaKeyListener = null;
+                                            }
+                                        }
+                                    }, 0);
+                        } catch (RemoteException e) {
+                            Log.w(TAG, "Failed to set death recipient " + user.mOnMediaKeyListener);
+                            user.mOnMediaKeyListener = null;
+                        }
+                    }
+                }
+            } finally {
+                Binder.restoreCallingIdentity(token);
+            }
+        }
+
         /**
          * Handles the dispatching of the volume button events to one of the
          * registered listeners. If there's a volume key long-press listener and
@@ -1127,13 +1168,7 @@
             }
         }
 
-        private void handleVoiceKeyEventLocked(KeyEvent keyEvent, boolean needWakeLock,
-                MediaSessionRecord session) {
-            if (session != null && session.hasFlag(MediaSession.FLAG_EXCLUSIVE_GLOBAL_PRIORITY)) {
-                // If the phone app has priority just give it the event
-                dispatchMediaKeyEventLocked(keyEvent, needWakeLock, session);
-                return;
-            }
+        private void handleVoiceKeyEventLocked(KeyEvent keyEvent, boolean needWakeLock) {
             int action = keyEvent.getAction();
             boolean isLongPress = (keyEvent.getFlags() & KeyEvent.FLAG_LONG_PRESS) != 0;
             if (action == KeyEvent.ACTION_DOWN) {
@@ -1150,15 +1185,52 @@
                     if (!mVoiceButtonHandled && !keyEvent.isCanceled()) {
                         // Resend the down then send this event through
                         KeyEvent downEvent = KeyEvent.changeAction(keyEvent, KeyEvent.ACTION_DOWN);
-                        dispatchMediaKeyEventLocked(downEvent, needWakeLock, session);
-                        dispatchMediaKeyEventLocked(keyEvent, needWakeLock, session);
+                        dispatchMediaKeyEventLocked(downEvent, needWakeLock, true);
+                        dispatchMediaKeyEventLocked(keyEvent, needWakeLock, true);
                     }
                 }
             }
         }
 
         private void dispatchMediaKeyEventLocked(KeyEvent keyEvent, boolean needWakeLock,
-                MediaSessionRecord session) {
+                boolean checkMediaKeyListener) {
+            // If we don't have a media button receiver to fall back on
+            // include non-playing sessions for dispatching.
+            boolean useNotPlayingSessions = true;
+            for (int userId : mCurrentUserIdList) {
+                UserRecord ur = mUserRecords.get(userId);
+                if (ur.mLastMediaButtonReceiver != null
+                        || ur.mRestoredMediaButtonReceiver != null) {
+                    useNotPlayingSessions = false;
+                    break;
+                }
+            }
+            if (DEBUG) {
+                Log.d(TAG, "dispatchMediaKeyEvent, useNotPlayingSessions="
+                        + useNotPlayingSessions);
+            }
+
+            MediaSessionRecord session = mPriorityStack.getDefaultMediaButtonSession(
+                    mCurrentUserIdList, useNotPlayingSessions);
+
+            if ((session == null
+                    || !session.hasFlag(MediaSession.FLAG_EXCLUSIVE_GLOBAL_PRIORITY))
+                    && checkMediaKeyListener) {
+                // Only consider full user.
+                UserRecord user = mUserRecords.get(mCurrentUserIdList.get(0));
+                if (user.mOnMediaKeyListener != null) {
+                    if (DEBUG_KEY_EVENT) {
+                        Log.d(TAG, "Send " + keyEvent + " to media key listener");
+                    }
+                    try {
+                        user.mOnMediaKeyListener.onMediaKey(keyEvent,
+                                new MediaKeyListenerResultReceiver(keyEvent, needWakeLock));
+                        return;
+                    } catch (RemoteException e) {
+                        Log.w(TAG, "Failed to send " + keyEvent + " to media key listener");
+                    }
+                }
+            }
             if (session != null) {
                 if (DEBUG_KEY_EVENT) {
                     Log.d(TAG, "Sending " + keyEvent + " to " + session);
@@ -1282,6 +1354,46 @@
                     && streamType <= AudioManager.STREAM_NOTIFICATION;
         }
 
+        private class MediaKeyListenerResultReceiver extends ResultReceiver implements Runnable {
+            private KeyEvent mKeyEvent;
+            private boolean mNeedWakeLock;
+            private boolean mHandled;
+
+            private MediaKeyListenerResultReceiver(KeyEvent keyEvent, boolean needWakeLock) {
+                super(mHandler);
+                mHandler.postDelayed(this, MEDIA_KEY_LISTENER_TIMEOUT);
+                mKeyEvent = keyEvent;
+                mNeedWakeLock = needWakeLock;
+            }
+
+            @Override
+            public void run() {
+                Log.d(TAG, "The media key listener is timed-out for " + mKeyEvent);
+                dispatchMediaKeyEvent();
+            }
+
+            @Override
+            protected void onReceiveResult(int resultCode, Bundle resultData) {
+                if (resultCode == MediaSessionManager.RESULT_MEDIA_KEY_HANDLED) {
+                    mHandled = true;
+                    mHandler.removeCallbacks(this);
+                    return;
+                }
+                dispatchMediaKeyEvent();
+            }
+
+            private void dispatchMediaKeyEvent() {
+                if (mHandled) {
+                    return;
+                }
+                mHandled = true;
+                mHandler.removeCallbacks(this);
+                synchronized (mLock) {
+                    dispatchMediaKeyEventLocked(mKeyEvent, mNeedWakeLock, false);
+                }
+            }
+        }
+
         private KeyEventWakeLockReceiver mKeyEventReceiver = new KeyEventWakeLockReceiver(mHandler);
 
         class KeyEventWakeLockReceiver extends ResultReceiver implements Runnable,