Create an Android™ client that publishes data through topics on the Diffusion™ server.

1. Set up a project in Android Studio that uses the Diffusion API.
   1. Create a new project using API Level 21 or later.
   2. Copy the diffusion-android-x.x.x.jar into the app/libs folder of your project.
   3. In Android Studio, right-click on the libs folder in the left-hand panel (the Project Tool Window), then select Add as Library.
      If the libs folder is not shown in the left-hand panel, use the pull-down menu at the top of the panel to select Project view.
2. In your project's AndroidManifest.xml file set the INTERNET permission.

   <uses-permission android:name="android.permission.INTERNET"/>

   Insert the element between the opening <manifest> tag and the opening <application> tag. This permission is required to use the Diffusion API.
3. Open your project's MainActivity.java file.
   This file is where you develop the code to interact with the Diffusion server.

   The empty MainActivity.java file contains the following boilerplate code:

   import android.support.v7.app.AppCompatActivity;
       import android.os.Bundle;
                   
       public class MainActivity extends AppCompatActivity {
                   
           @Override
           protected void onCreate(Bundle savedInstanceState) {
               super.onCreate(savedInstanceState);
               setContentView(R.layout.activity_main);
           }
       }

4. Import the following packages and classes:

   import android.support.v7.app.AppCompatActivity;
   import android.os.Bundle;
   import android.util.Log;
   
   import com.pushtechnology.diffusion.client.Diffusion;
   import com.pushtechnology.diffusion.client.callbacks.ErrorReason;
   import com.pushtechnology.diffusion.client.features.Topics;
   import com.pushtechnology.diffusion.client.features.control.topics.TopicControl;
   import com.pushtechnology.diffusion.client.features.control.topics.TopicUpdateControl;
   import com.pushtechnology.diffusion.client.session.Session;
   import com.pushtechnology.diffusion.client.session.SessionFactory;
   import com.pushtechnology.diffusion.client.topics.details.TopicType;
   import com.pushtechnology.diffusion.datatype.json.JSON;
   import com.pushtechnology.diffusion.datatype.json.JSONDataType;
   
   import java.util.concurrent.Executors;
   import java.util.concurrent.TimeUnit;
   import java.util.concurrent.atomic.AtomicInteger;
             
   public class MainActivity extends AppCompatActivity {
   
   }

   The com.pushtechnology.diffusion.client packages contain the classes to use to interact with the Diffusion server.

5. Create a SessionHandler inner class that implements SessionFactory.OpenCallback.
   This inner class will contain the code that interacts with the Diffusion server.

       private class SessionHandler implements SessionFactory.OpenCallback {
           private Session session = null;
   
           @Override
           public void onOpened(Session session) {
               this.session = session;
           }
   
           @Override
           public void onError(ErrorReason errorReason) {
               
           }
   
           public void close() {
               if ( session != null ) {
                   session.close();
               }
           }
       }

6. In the onOpened method, add the code required to create the foo/counter topic and update it with an incrementing value.
   1. Use the TopicControl feature to create a JSON topic.

                  // Create a JSON topic 'foo/counter'
                  session.feature(TopicControl.class).addTopic(
                      "foo/counter",
                      TopicType.JSON,
                      new TopicControl.AddCallback.Default());

   2. Get the TopicUpdateControl feature and JSON data type.

                   // Get the TopicUpdateControl feature and JSON data type
                   final JSONDataType jsonDataType = Diffusion.dataTypes().json();
                   final TopicUpdateControl updateControl = session
                   .feature(TopicUpdateControl.class);

   3. Loop once a second updating the foo/counter topic with an incrementing count from 0 to 1000.
      Use the non-exclusive updateControl.updater().update() method to update the topic while still allowing other clients to update the topic.

                final AtomicInteger i = new AtomicInteger(0);
                
                Executors.newSingleThreadScheduledExecutor().scheduleAtFixedRate(new Runnable() {
                    @Override
                    public void run() {
                    // Create the json value
                    final JSON value = jsonDataType.fromJsonString(
                        String.format("{\"count\" : %d }", i.getAndIncrement()));
                
                    // Update the topic
                    updateControl.updater().update(
                    "counter",
                    value,
                    new TopicUpdateControl.Updater.UpdateCallback.Default());
                    }
                }, 1000, 1000, TimeUnit.MILLISECONDS);
                  

7. In the MainActivity class, declare an instance of session handler.

       private SessionHandler sessionHandler = null;

8. Override the onCreate method of the MainActivity class to open the session with the Diffusion server.

       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
                 
           if (sessionHandler == null) {
               sessionHandler = new SessionHandler();
                 
               Diffusion.sessions()
                 .principal("username")
                 .password("password")
                 .open("ws://host:port", sessionHandler);
                 }
           }

   Or you can connect securely, using Secure Sockets Layer (SSL):

       Diffusion.sessions().principal("principal").password("password").open("wss://host:port", sessionHandler);

   Replace the host, port, principal, and password values with your own information.
9. Override the onDestroy method of the MainActivity class to close the session with the Diffusion server.

           if ( sessionHandler != null ) {
               sessionHandler.close();
               sessionHandler = null;
           }
           super.onDestroy();

10. Compile and run your client.

package com.pushtechnology.demo.update;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import com.pushtechnology.diffusion.client.Diffusion;
import com.pushtechnology.diffusion.client.callbacks.ErrorReason;
import com.pushtechnology.diffusion.client.features.Topics;
import com.pushtechnology.diffusion.client.features.control.topics.TopicControl;
import com.pushtechnology.diffusion.client.features.control.topics.TopicUpdateControl;
import com.pushtechnology.diffusion.client.session.Session;
import com.pushtechnology.diffusion.client.session.SessionFactory;
import com.pushtechnology.diffusion.client.topics.details.TopicType;
import com.pushtechnology.diffusion.datatype.json.JSON;
import com.pushtechnology.diffusion.datatype.json.JSONDataType;

import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

public class MainActivity extends AppCompatActivity {

    /**
     * A session handler that maintains the diffusion session.
     */
    private class SessionHandler implements SessionFactory.OpenCallback {
        private Session session = null;

        @Override
        public void onOpened(Session session) {
            this.session = session;


            // Create a JSON topic 'foo/counter'
            session.feature(TopicControl.class).addTopic(
                "foo/counter",
                TopicType.JSON,
                new TopicControl.AddCallback.Default());


            // Get the TopicUpdateControl feature and JSON data type
            final JSONDataType jsonDataType = Diffusion.dataTypes().json();
            final TopicUpdateControl updateControl = session
                    .feature(TopicUpdateControl.class);


            final AtomicInteger i = new AtomicInteger(0);

            // Schedule a recurring task that increments the counter and updates the "counter" topic with a json value
            // every second
            Executors.newSingleThreadScheduledExecutor().scheduleAtFixedRate(new Runnable() {
                @Override
                public void run() {
                    // Create the json value
                    final JSON value = jsonDataType.fromJsonString(
                        String.format("{\"count\" : %d }", i.getAndIncrement()));
            
                    // Update the topic
                    updateControl.updater().update(
                        "counter",
                        value,
                        new TopicUpdateControl.Updater.UpdateCallback.Default());
                }
            }, 1000, 1000, TimeUnit.MILLISECONDS);
        }

        @Override
        public void onError(ErrorReason errorReason) {
            Log.e("Diffusion", "Failed to open session because: " + errorReason.toString());
            session = null;
        }

        public void close() {
            if (session != null) {
                session.close();
            }
        }
    }

    private SessionHandler sessionHandler = null;

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

        if (sessionHandler == null) {
            sessionHandler = new SessionHandler();

            Diffusion.sessions()
                     .principal("username")
                     .password("password")
                     .open("ws://host:port", sessionHandler);
        }
    }

    @Override
    protected void onDestroy() {
        if (sessionHandler != null) {
            sessionHandler.close();
            sessionHandler = null;
        }

        super.onDestroy();
    }
}