How to see what a user is typing in an Android chat app

“Clement is typing…”

Have you ever kept staring at your mobile screen waiting for the other person’s reply while she is typing…

With the rise of instant chat, we see this daily in one platform or the other. Typing indicator makes you aware that the other person is responding to your message.

You are 3 steps away to implement typing indicator in your chat app and they are below:

Attach a text change listener to the text view.
Publish and subscribe typing status of the user
Update typing status real time on UI

Step 1: Attach a text change listener

TextWatcher’s afterTextChanged method is called to notify you that, somewhere within EditText, the text has been changed.

If text is changed and

length is 1 that means typing is started,
length is 0 means typing is stopped.

Sample android code:

messageEditText.addTextChangedListener(new TextWatcher() {

public void beforeTextChanged(CharSequence s, int start, int count, int after) {

}

public void onTextChanged(CharSequence s, int start, int before, int count) {

}

public void afterTextChanged(Editable s) {

if (!TextUtils.isEmpty(s.toString()) && s.toString().trim().length() == 1) {

//Log.i(TAG, “typing started event…”);

typingStarted = true;

//send typing started status

} else if (s.toString().trim().length() == 0 && typingStarted) {

//Log.i(TAG, “typing stopped event…”);

typingStarted = false;

//send typing stopped status

}

});

Source: Github Applozic Android Chat SDK

Lo stato di battitura dovrebbe essere fermato in pochi altri casi come:

i) Se l'app va in background,

ii) EditText perde il focus, o

iii) La lunghezza del testo digitato rimane la stessa per un certo tempo.

Step 2: Pubblicare e sottoscrivere lo stato di battitura dell'utente

E' ora di inviare e ricevere lo stato di battitura all'altro dispositivo. Questo può essere implementato usando il modello publish-subscribe. Capiamo cos'è il pattern publish-subscribe.

publish-subscribe è un pattern di messaggistica in cui i mittenti dei messaggi, chiamati editori, non programmano i messaggi da inviare direttamente a specifici destinatari, chiamati sottoscrittori, ma invece caratterizzano i messaggi pubblicati in classi senza sapere quali sottoscrittori, se ce ne sono, possono esserci. Allo stesso modo, gli abbonati esprimono interesse per una o più classi e ricevono solo i messaggi che sono di interesse, senza sapere quali editori, se ci sono.

Fonte: Wikipedia

Now, all we have to do is:

Subscribe user A’s app to a topic “/topic/user-a”, user B’s app to a topic “/topic/user-b” and publish the typing status to receiver’s topic.

User A

User B

/topic/user-a

/topic/user-b

Publish

/topic/user-b

/topic/user-a

Typing started

Typing stopped

In order to send data from one device to another device in real time, we will require a socket based connection. There are many options available like Socket.io, Mosquitto.org, RabbitMQ.

For this tutorial, we will use RabbitMQ.

Run RabbitMQ MQTT Adapter on your server.

On android, use the eclipse paho library to create mqtt client.

org.eclipse.paho.android.service–1.0.2.jar

org.eclipse.paho.client.mqttv3-1.0.2.jar

Above 2 versions for eclipse paho android client can be found here: https://github.com/AppLozic/Applozic-Android-SDK/tree/master/mobicomkit/libs

Android code to publish data:

MqttClient client = new MqttClient(MQTT_URL, userId + “-” + new Date().getTime(), new MemoryPersistence());

MqttMessage message = new MqttMessage();

message.setRetained(false);

message.setPayload(typingStatus).getBytes());

message.setQos(0);

client.publish(“topic/” + userId, message);

client.subscribe(“topic/” + userB, 0);

Source: Github Applozic Android Chat SDK

Step 3: Update typing status real time on UI

At the receiver’s end, upon receiving typing status, show and hide the typing indicator accordingly.

Below is the android code to receive the typing status

@Override

public void messageArrived(String s,final MqttMessage mqttMessage) throwsException {

Log.i(TAG, “Received MQTT message: ” + newString(mqttMessage.getPayload()));

….

if (!TextUtils.isEmpty(s) && s.startsWith(TYPINGTOPIC)) {

String typingResponse = mqttMessage.toString();

// Broadcast typing status to the current activity/fragment and display the typing label.

}

…

}