Get started with RabbitMQ on Android (Android Studio)

We need to include the RabbitMQ Java Client Library and reference the jar files into the project. In Android Studio you can create a libs folder in the same level as the app. Copy and past the jars in to this libs folder. Mark all the jar files and press "Add As Library..." as seen in the image below.

You can confirm that the libs has been added as library by opening build.gradle and check under dependencies, all files should seen be there.

dependencies {
  ...
  compile files('libs/rabbitmq-client.jar')
  ...
}

NOTE: Only if you are using Android Gradle plugin 0.7.0 and do get the error "Duplicate files copied in APK" when you later run your application, you need to add packagingOptions to your build.gradle file as specified in here.

android {
  packagingOptions {
    exclude 'META-INF/LICENSE.txt'
    exclude 'META-INF/NOTICE.txt'
  }
}

3. Android Manifest, internet permission

We need to tell the Android system that this app is allowed to access internet. Open the AndroidManifest.xml file, located in the root of the project. Add the user permission android.permission.INTERNET just before the closing /manifest tag.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.cloudamqp.rabbitmq"
     android:versionCode="1"
     android:versionName="1.0">
     ......
     <uses-permission android:name="android.permission.INTERNET"></uses-permission>
</manifest>

4. Start coding

Layout

Create the view for the application. The .xml layout file can be found under res->layout. What we have here is a root ScrollView containing a

EditText a Button and a TextView The EditText will be used as an input field for the text that will be sent. The text will be published when the button is pressed and all messages received by the subscriber will be printed to the TextView.

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
  ...
  <EditText
  android:id="@+id/text"
  android:layout_width="fill_parent"
  android:background="#ffffff"
  android:hint="Enter a message" />

  <Button
  android:id="@+id/publish"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:layout_below="@+id/text"
  android:text="Publish message" />

  <TextView
  android:id="@+id/textView"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:layout_below="@+id/publish"
  android:textColor="#000000" />
  ...
</ScrollView>

Publish

Create an internal message queue. In this case is a BlockingDeque used. Blockingqueues implementations are designed to be used primarily for producer-consumer queues.

private BlockingDeque<String> queue = new LinkedBlockingDeque>String>();
void publishMessage(String message) {
  try {
    Log.d("","[q] " + message);
    queue.putLast(message);
  } catch (InterruptedException e) {
    e.printStackTrace();
  }
}

Create a setup function for the ConnectionFactory The connection factory encapsulates a set of connection configuration parameters, in this case the CLOUDAMQP_URL. The URL can be found in the control panel for your instance.

ConnectionFactory factory = new ConnectionFactory();
private void setupConnectionFactory() {
  String uri = "CLOUDAMQP_URL";
  try {
    factory.setAutomaticRecoveryEnabled(false);
    factory.setUri(uri);
  } catch (KeyManagementException | NoSuchAlgorithmException | URISyntaxException e1) {
    e1.printStackTrace();
}

Create a publisher that publish messages from the internal queue. Messages are added back to the queue if an exception is catched. The publisher will try to reconnect every 5 seconds if the connection is broken.

A thread ("background" or "worker" threads or use of the AsyncTask class) is needed when we have operations to perform that are not instantaneous, such as network access when connecting to rabbitMQ.

We will use a fanout exchange. A fanout exchange routes messages to all of the queues that are bound to it and the routing key is ignored. If N queues are bound to a fanout exchange, will a new message that is published to that exchange, be copied and delivered to all N queues. Fanout exchanges are ideal for the broadcast routing of messages.

public void publishToAMQP()
{
  publishThread = new Thread(new Runnable() {
    @Override
    public void run() {
      while(true) {
        try {
          Connection connection = factory.newConnection();
          Channel ch = connection.createChannel();
          ch.confirmSelect();

          while (true) {
            String message = queue.takeFirst();
            try{
              ch.basicPublish("amq.fanout", "chat", null, message.getBytes());
              Log.d("", "[s] " + message);
              ch.waitForConfirmsOrDie();
            } catch (Exception e){
              Log.d("","[f] " + message);
              queue.putFirst(message);
              throw e;
           }
         }
       } catch (InterruptedException e) {
         break;
       } catch (Exception e) {
         Log.d("", "Connection broken: " + e.getClass().getName());
         try {
           Thread.sleep(5000); //sleep and then try again
         } catch (InterruptedException e1) {
           break;
         }
       }
     }
   }
  });
  publishThread.start();
}

void subscribe(final Handler handler)
{
  subscribeThread = new Thread(new Runnable() {
    @Override
    public void run() {
      while(true) {
        try {
          Connection connection = factory.newConnection();
          Channel channel = connection.createChannel();
          channel.basicQos(1);
          DeclareOk q = channel.queueDeclare();
          channel.queueBind(q.getQueue(), "amq.fanout", "chat");
          QueueingConsumer consumer = new QueueingConsumer(channel);
          channel.basicConsume(q.getQueue(), true, consumer);

          while (true) {
            QueueingConsumer.Delivery delivery = consumer.nextDelivery();
            String message = new String(delivery.getBody());
            Log.d("","[r] " + message);
            Message msg = handler.obtainMessage();
            Bundle bundle = new Bundle();
            bundle.putString("msg", message);
            msg.setData(bundle);
            handler.sendMessage(msg);
          }
        } catch (InterruptedException e) {
          break;
        } catch (Exception e1) {
          Log.d("", "Connection broken: " + e1.getClass().getName());
          try {
            Thread.sleep(5000); //sleep and then try again
          } catch (InterruptedException e) {
            break;
          }
        }
      }
    }
  });
  subscribeThread.start();
}

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

  setupConnectionFactory();
  publishToAMQP();
  setupPubButton();

  final Handler incomingMessageHandler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
      String message = msg.getData().getString("msg");
      TextView tv = (TextView) findViewById(R.id.textView);
      Date now = new Date();
      SimpleDateFormat ft = new SimpleDateFormat ("hh:mm:ss");
      tv.append(ft.format(now) + ' ' + message + '\n');
    }
  };
  subscribe(incomingMessageHandler);
}

void setupPubButton() {
  Button button = (Button) findViewById(R.id.publish);
  button.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View arg0) {
      EditText et = (EditText) findViewById(R.id.text);
      publishMessage(et.getText().toString());
      et.setText("");
   }
  });
}

Thread subscribeThread;
Thread publishThread;
@Override
protected void onDestroy() {
  super.onDestroy();
  publishThread.interrupt();
  subscribeThread.interrupt();
}