Subscribing to other client streams

We want clients to be able to subscribe to (or view) other clients’ streams in the session:

1. Add a subscriber property to the MainActivity class (after the declaration of the publisher property):

private var subscriber: Subscriber? = null

The Subscriber class is defined in the Android SDK. It defines an object that a client uses to subscribe to (view) a stream published by another client.

2. Modify the implementation of the onStreamReceived(session, stream) method (one of the SessionListener callbacks) to include code to subscribe to other clients’ streams the session:

override fun onStreamReceived(session: Session, stream: Stream) {
    Log.d(TAG, "onStreamReceived: New Stream Received ${stream.streamId} in session: ${session.sessionId}")

    if (subscriber == null) {
        val newSubscriber = Subscriber.Builder(this@MainActivity, stream).build().apply {
            renderer.setStyle(
                BaseVideoRenderer.STYLE_VIDEO_SCALE,
                BaseVideoRenderer.STYLE_VIDEO_FILL
            )
            setSubscriberListener(subscriberListener)
        }

        session.subscribe(newSubscriber)
        subscriber = newSubscriber
        subscriberView = newSubscriber.view
    }
}

• Subscriber.Builder() creates a new subscriber for the given Stream.
• setSubscriberListener() attaches a listener for stream events.
• session.subscribe() starts the subscription to the remote stream.
• subscriberView = newSubscriber.view places the video view into your layout.

3. To log events Add subscriberListener property below sessionListener of the MainActivity:

private val subscriberListener = object : SubscriberKit.SubscriberListener {
    override fun onConnected(subscriberKit: SubscriberKit) {
        Log.d(TAG, "onConnected: Subscriber connected. Stream: ${subscriberKit.stream?.streamId}")
    }

    override fun onDisconnected(subscriberKit: SubscriberKit) {
        Log.d(TAG, "onDisconnected: Subscriber disconnected. Stream: ${subscriberKit.stream?.streamId}")
    }

    override fun onError(subscriberKit: SubscriberKit, opentokError: OpentokError) {
        Log.e(TAG, "SubscriberKit onError: ${opentokError.message}")
    }
}

When another client publishes a stream to a session, this method is called, and a Stream object is passed in. The Stream class is defined in the Android SDK, and it represents an audio-video stream in the session.

The code initializes an instance of the Subscriber class, defined in the Android SDK. The Subscriber.Builder() constructor takes two parameters:

• The Android application context associated with this process.
• The Stream object (for the stream you want to view)

The Session.subscribe(subscriber) method subscribes to the stream that was received.

4. Modify the implementation of the onStreamDropped(Session session, Stream stream) method (another one of the SessionListener callbacks):

override fun onStreamDropped(session: Session, stream: Stream) {
    Log.i(TAG, "onStreamDropped: Stream dropped with ID: ${stream.streamId}")

    subscriber?.let {
        subscriberView = null
        subscriber = null
    }
}

subscriberView = null removes a subscriber's view once the stream has dropped.