Notify Attendees in Realtime - Android

When doing livestream, you may want to broadcast message to all the viewers at once.

Let us see, how we can use PubSub to implement this functionality. If you are not familiar with the PubSub mechanism, you can follow this guide.

Notifying Attendees

1. We will be publish the message that the sender typed in the EditText field to the topic NOTIFY_ATTENDEES.

Kotlin

class SpeakerActivity : AppCompatActivity() {
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    //...
    findViewById(R.id.btnSend).setOnClickListener(view -> sendMessage());
  }

  private fun sendMessage() {
    // get message from EditText
    val message: String = etmessage.getText().toString()
    if (!TextUtils.isEmpty(message)) {
        val publishOptions = PubSubPublishOptions()
        publishOptions.setPersist(true)

        // Sending the Message using the publish method
        meeting!!.pubSub.publish("NOTIFY_ATTENDEES", message, publishOptions)

        // Clearing the message input
        etmessage.setText("")
    } else {
        Toast.makeText(
            this@SpeakerActivity, "Please Enter Message",
            Toast.LENGTH_SHORT
        ).show()
    }
  }
}

Java

public class SpeakerActivity extends AppCompatActivity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //...
    findViewById(R.id.btnSend).setOnClickListener(view -> sendMessage());
  }

  private void sendMessage()
  {
    // get message from EditText
    String message = etmessage.getText().toString();
    if (!message.equals("")) {
        PubSubPublishOptions publishOptions = new PubSubPublishOptions();
        publishOptions.setPersist(true);

        // Sending the Message using the publish method
        meeting.pubSub.publish("NOTIFY_ATTENDEES", message, publishOptions);

        // Clearing the message input
        etmessage.setText("");
    } else {
        Toast.makeText(SpeakerActivity.this, "Please Enter Message",
                Toast.LENGTH_SHORT).show();
    }
  }
}

2. Now let us show an alert to all the viewers displaying the message posted by the speaker.

Kotlin

class ViewerActivity : AppCompatActivity() {

  // PubSubMessageListener
  var pubSubMessageListener =
    PubSubMessageListener { message ->
      if(meeting!!.localparticipant.mode == "SIGNALLING_ONLY"){
        Toast.makeText(
                this@ViewerActivity, message.message,
                Toast.LENGTH_SHORT
            ).show()
      }
  }

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_chat)

    //...

    // Subscribe for 'NOTIFY_ATTENDEES' topic
    val pubSubMessageList = meeting!!.pubSub.subscribe("NOTIFY_ATTENDEES", pubSubMessageListener)

    for (message in pubSubMessageList) {
      // Persisted messages
      if(meeting!!.localparticipant.mode == "SIGNALLING_ONLY"){
        Toast.makeText(
                this@ViewerActivity, message.message,
                Toast.LENGTH_SHORT
            ).show()
      }
    }
  }
}

Java

public class ViewerActivity extends AppCompatActivity {

  // PubSubMessageListener
  private PubSubMessageListener pubSubMessageListener = new PubSubMessageListener() {
    @Override
    public void onMessageReceived(PubSubMessage message) {
        if(meeting.getLocalParticipant().getMode() == "SIGNALLING_ONLY"){
            Toast.makeText(
                ViewerActivity.this, message.getMessage(),
                Toast.LENGTH_SHORT
                ).show();
        }
    }
  };

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //..

    // Subscribe for 'NOTIFY_ATTENDEES' topic
    List<PubSubMessage> pubSubMessageList = meeting.pubSub.subscribe("NOTIFY_ATTENDEES", pubSubMessageListener);

    for(PubSubMessage message : pubSubMessageList){
        // Persisted messages
        if(meeting.getLocalParticipant().getMode() == "SIGNALLING_ONLY"){
            Toast.makeText(
            ViewerActivity.this, message.getMessage(),
            Toast.LENGTH_SHORT
            ).show();
        }
    }
  }
}

API Reference

The API references for all the methods and events utilised in this guide are provided below.

• pubSub()