Created a java wrapper for the callback OnAddTrack to PeerConnection.Observer

webrtc/api/android/jni/peerconnection_jni.cc

 /*
  *  Copyright 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 155 matching lines @@
   // the below methods and we only override one of them.
   // TODO(deadbeef): Remove once there's only one version of the methods.
   using PeerConnectionObserver::OnAddStream;
   using PeerConnectionObserver::OnRemoveStream;
   using PeerConnectionObserver::OnDataChannel;
 
   PCOJava(JNIEnv* jni, jobject j_observer)
       : j_observer_global_(jni, j_observer),
         j_observer_class_(jni, GetObjectClass(jni, *j_observer_global_)),
         j_media_stream_class_(jni, FindClass(jni, "org/webrtc/MediaStream")),
-        j_media_stream_ctor_(GetMethodID(
-            jni, *j_media_stream_class_, "<init>", "(J)V")),
+        j_media_stream_ctor_(
+            GetMethodID(jni, *j_media_stream_class_, "<init>", "(J)V")),
         j_audio_track_class_(jni, FindClass(jni, "org/webrtc/AudioTrack")),
-        j_audio_track_ctor_(GetMethodID(
-            jni, *j_audio_track_class_, "<init>", "(J)V")),
+        j_audio_track_ctor_(
+            GetMethodID(jni, *j_audio_track_class_, "<init>", "(J)V")),
         j_video_track_class_(jni, FindClass(jni, "org/webrtc/VideoTrack")),
-        j_video_track_ctor_(GetMethodID(
-            jni, *j_video_track_class_, "<init>", "(J)V")),
+        j_video_track_ctor_(
+            GetMethodID(jni, *j_video_track_class_, "<init>", "(J)V")),
         j_data_channel_class_(jni, FindClass(jni, "org/webrtc/DataChannel")),
-        j_data_channel_ctor_(GetMethodID(
-            jni, *j_data_channel_class_, "<init>", "(J)V")) {
-  }
+        j_data_channel_ctor_(
+            GetMethodID(jni, *j_data_channel_class_, "<init>", "(J)V")),
+        j_rtp_receiver_class_(jni, FindClass(jni, "org/webrtc/RtpReceiver")),
+        j_rtp_receiver_ctor_(
+            GetMethodID(jni, *j_rtp_receiver_class_, "<init>", "(J)V")) {}
 
   virtual ~PCOJava() {
     ScopedLocalRefFrame local_ref_frame(jni());
     while (!remote_streams_.empty())
       DisposeRemoteStream(remote_streams_.begin());
   }
 
   void OnIceCandidate(const IceCandidateInterface* candidate) override {
     ScopedLocalRefFrame local_ref_frame(jni());
     std::string sdp;
@@ skipping 169 matching lines @@
   }
 
   void OnRenegotiationNeeded() override {
     ScopedLocalRefFrame local_ref_frame(jni());
     jmethodID m =
         GetMethodID(jni(), *j_observer_class_, "onRenegotiationNeeded", "()V");
     jni()->CallVoidMethod(*j_observer_global_, m);
     CHECK_EXCEPTION(jni()) << "error during CallVoidMethod";
   }
 
+  void OnAddTrack(
+      rtc::scoped_refptr<RtpReceiverInterface> receiver,
+      std::vector<rtc::scoped_refptr<MediaStreamInterface>> streams) override {
+    ScopedLocalRefFrame local_ref_frame(jni());
+    jobject j_rtp_receiver = jni()->NewObject(
+        *j_rtp_receiver_class_, j_rtp_receiver_ctor_, (jlong)receiver.get());
+    CHECK_EXCEPTION(jni()) << "error during NewObject";

[Taylor Brandstetter, 2016/11/17 23:02:53]

Need to call receiver->AddRef() after this, like in nativeGetReceivers.

[Zhi Huang, 2016/11/18 02:22:11]

Good catch! This could be a potential problem.

+
+    jobjectArray j_stream_array = ToJavaMediaStreamArray(jni(), streams);
+    jmethodID m =
+        GetMethodID(jni(), *j_observer_class_, "onAddTrack",
+                    "(Lorg/webrtc/RtpReceiver;[Lorg/webrtc/MediaStream;)V");
+    jni()->CallVoidMethod(*j_observer_global_, m, j_rtp_receiver,
+                          j_stream_array);
+    CHECK_EXCEPTION(jni()) << "Error during CallVoidMethod";
+  }
+
   void SetConstraints(ConstraintsWrapper* constraints) {
     RTC_CHECK(!constraints_.get()) << "constraints already set!";
     constraints_.reset(constraints);
   }
 
   const ConstraintsWrapper* constraints() { return constraints_.get(); }
 
  private:
   typedef std::map<MediaStreamInterface*, jobject> NativeToJavaStreamsMap;
 
@@ skipping 29 matching lines @@
     jobjectArray java_candidates =
         jni->NewObjectArray(candidates.size(), candidate_class, NULL);
     int i = 0;
     for (const cricket::Candidate& candidate : candidates) {
       jobject j_candidate = ToJavaCandidate(jni, &candidate_class, candidate);
       jni->SetObjectArrayElement(java_candidates, i++, j_candidate);
     }
     return java_candidates;
   }
 
+  jobjectArray ToJavaMediaStreamArray(
+      JNIEnv* jni,
+      std::vector<rtc::scoped_refptr<MediaStreamInterface>> streams) {
+    jobjectArray java_streams =
+        jni->NewObjectArray(streams.size(), *j_media_stream_class_, nullptr);
+    int i = 0;
+    for (rtc::scoped_refptr<MediaStreamInterface> stream : streams) {
+      NativeToJavaStreamsMap::iterator it = remote_streams_.find(stream);
+      if (it != remote_streams_.end()) {
+        jobject j_stream = it->second;
+        CHECK_EXCEPTION(jni) << "error during NewObject";

[Taylor Brandstetter, 2016/11/17 23:02:53]

I think this CHECK_EXCEPTION needs to be right after "NewObjectArray". And the
message should be "error during NewObjectArray".

[Zhi Huang, 2016/11/18 02:22:10]

Done.

+        jni->SetObjectArrayElement(java_streams, i++, j_stream);
+      }

[Taylor Brandstetter, 2016/11/17 23:02:53]

There should be an "else" with an RTC_DCHECK.

[Zhi Huang, 2016/11/18 02:22:10]

What about always creating new stream if we cannot find one in the map?

+    }
+    return java_streams;
+  }
+
   JNIEnv* jni() {
     return AttachCurrentThreadIfNeeded();
   }
 
   const ScopedGlobalRef<jobject> j_observer_global_;
   const ScopedGlobalRef<jclass> j_observer_class_;
   const ScopedGlobalRef<jclass> j_media_stream_class_;
   const jmethodID j_media_stream_ctor_;
   const ScopedGlobalRef<jclass> j_audio_track_class_;
   const jmethodID j_audio_track_ctor_;
   const ScopedGlobalRef<jclass> j_video_track_class_;
   const jmethodID j_video_track_ctor_;
   const ScopedGlobalRef<jclass> j_data_channel_class_;
   const jmethodID j_data_channel_ctor_;
+  const ScopedGlobalRef<jclass> j_rtp_receiver_class_;
+  const jmethodID j_rtp_receiver_ctor_;
   // C++ -> Java remote streams. The stored jobects are global refs and must be
   // manually deleted upon removal. Use DisposeRemoteStream().
   NativeToJavaStreamsMap remote_streams_;
   std::unique_ptr<ConstraintsWrapper> constraints_;
 };
 
 // Wrapper for a Java MediaConstraints object.  Copies all needed data so when
 // the constructor returns the Java object is no longer needed.
 class ConstraintsWrapper : public MediaConstraintsInterface {
  public:
@@ skipping 1456 matching lines @@
   jclass j_array_list_class = FindClass(jni, "java/util/ArrayList");
   jmethodID j_array_list_ctor =
       GetMethodID(jni, j_array_list_class, "<init>", "()V");
   jmethodID j_array_list_add =
       GetMethodID(jni, j_array_list_class, "add", "(Ljava/lang/Object;)Z");
   jobject j_receivers = jni->NewObject(j_array_list_class, j_array_list_ctor);
   CHECK_EXCEPTION(jni) << "error during NewObject";
 
   jclass j_rtp_receiver_class = FindClass(jni, "org/webrtc/RtpReceiver");
   jmethodID j_rtp_receiver_ctor =
       GetMethodID(jni, j_rtp_receiver_class, "<init>", "(J)V");

[Taylor Brandstetter, 2016/11/17 23:02:53]

Can now use j_rtp_receiver_class_ and j_rtp_receiver_ctor_ here.

[Zhi Huang, 2016/11/18 02:22:11]

They are not in the same scope

 
   auto receivers = ExtractNativePC(jni, j_pc)->GetReceivers();
   for (const auto& receiver : receivers) {
     jlong nativeReceiverPtr = jlongFromPointer(receiver.get());
     jobject j_receiver = jni->NewObject(j_rtp_receiver_class,
                                         j_rtp_receiver_ctor, nativeReceiverPtr);
     CHECK_EXCEPTION(jni) << "error during NewObject";
     // Receiver is now owned by Java object, and will be freed from there.
     receiver->AddRef();
     jni->CallBooleanMethod(j_receivers, j_array_list_add, j_receiver);
@@ skipping 478 matching lines @@
   return JavaStringFromStdString(
       jni,
       reinterpret_cast<RtpReceiverInterface*>(j_rtp_receiver_pointer)->id());
 }
 
 JOW(void, RtpReceiver_free)(JNIEnv* jni, jclass, jlong j_rtp_receiver_pointer) {
   reinterpret_cast<RtpReceiverInterface*>(j_rtp_receiver_pointer)->Release();
 }
 
 }  // namespace webrtc_jni