1. Import the required classes and interfaces.

   import net.rim.blackberry.api.bbm.platform.*;
   import net.rim.blackberry.api.bbm.platform.io.*;
   import net.rim.blackberry.api.bbm.platform.profile.*;
   import net.rim.blackberry.api.bbm.platform.service.*;
   import net.rim.device.api.ui.component.*;

2. Create a class that extends MainScreen. In the constructor for this screen class, pass in the application's associated BBMPlatformContext.

   public class MyBBMScreen extends MainScreen
   {
       public MyBBMScreen(BBMPlatformContext platformContext)
       {
   
       }
   }

3. Declare an instance of BBMPlatformChannel as a member variable of the MyBBMScreen class.

   public class MyBBMScreen extends MainScreen
   {
       BBMPlatformChannel _channel;
   
       public MyBBMScreen(BBMPlatformContext platformContext)
       {
           
       }
   }

4. In the MyBBMScreen constructor, retrieve an instance of the messaging service.

   public MyBBMScreen(BBMPlatformContext platformContext)
   {
       MessagingService myMessagingService = platformContext.getMessagingService();
   }

5. Create a channel passing in an instance of a BBMPlatformChannelListener that you will define in step 9.

   public MyBBMScreen(BBMPlatformContext platformContext)
   {
       MessagingService myMessagingService = platformContext.getMessagingService();
   
       _channel = messagingService.createChannel(_channelListener);
   }

6. Invite a contact to your application. In the parameters for sendInvitation(), you can specify a message to be delivered when the contact receives the invitation, a parameter that will be passed to the application's main method as args[1], and an expiry time. The following code sample passes in the value 0 for expiry time (that is, the invitation never expires). A Contact picker UI component opens for the user to choose a contact to invite.

   public MyBBMScreen(BBMPlatformContext platformContext)
   {
       MessagingService messagingService = platformContext.getMessagingService();
       _channel = messagingService.createChannel(_channelListener);
           
       _channel.sendInvitation("Let's play a game", "Chess App", 0);
   }

7. In the MyBBMScreen class, define a helper method, onContactJoined(), which the BBMPlatformChannelListener.contactJoined() callback method invokes. Pass in a reference to the contact who has just joined.

   public class MyBBMScreen extends MainScreen
   {
       BBMPlatformChannel _channel;
   
       public MyBBMScreen(BBMPlatformContext platformContext)
       {
           //code from steps 5 to 7    
       }
      
       private onContactJoined(BBMPlatformContact contact)
       {
   
       }
   }

8. In the onContactJoined() method, create a message, wrap it in a BBMPlatformData object, and, in a try-catch block, send the message. In the following code sample, the message is sent to all contacts who have joined the channel, informing that a participant has left the game.

   private void onContactLeft(BBMPlatformContact contact)
   {
       String goodbyeMsg = contact.getDisplayName() + " has left the game.";
       BBMPlatformData data = new BBMPlatformData(goodbyeMsg);
   
       try {
           _channel.sendData(data, _channel.getContactList());
       }
       catch (BBMPlatformException e) 
       {
           // Error handler code
       }
   }

9. In the MyBBMScreen class, define the channel listener, _channelListener, as a private inner class. In the contactJoined() method, invoke the onContactJoined() method passing in the BBMPlatformContact that just joined.

   public class MyBBMScreen extends MainScreen
   {
       public MyBBMScreen(BBMPlatformContext platformContext)
       {
           //code from steps 4 to 6
       }
   
       private void onContactJoined(BBMPlatformContact contact) 
       {
           //code from step 8
       }
   
       private BBMPlatformChannelListener _channelListener = new BBMPlatformChannelListener() 
       {
           public void contactsInvited(BBMPlatformConnection conn, BBMPlatformContactList 
                                        contactList) 
           {
           }
            
           public void contactsJoined(BBMPlatformConnection conn, BBMPlatformContactList
                                      contacts, String cookie, int type) 
           {
           }
   
           public void contactDeclined(BBMPlatformConnection conn, 
                                        BBMPlatformContact contact) 
           {
           }
        
           public void contactLeft(BBMPlatformConnection conn, BBMPlatformContact contact) 
           {
               onContactLeft(contact);
           }
          
           public void dataReceived(BBMPlatformConnection conn, BBMPlatformContact sender, 
                                     BBMPlatformData data) 
           {
           }
           
      			  }
       };
   }

Code sample: Sending a message to a contact

import net.rim.blackberry.api.bbm.platform.*;
import net.rim.blackberry.api.bbm.platform.io.*;
import net.rim.blackberry.api.bbm.platform.profile.*;
import net.rim.blackberry.api.bbm.platform.service.*;
import net.rim.device.api.ui.component.*;

public class MyBBMScreen extends MainScreen
{
    public MyBBMScreen(BBMPlatformContext platformContext)
    {
        MessagingService messagingService = platformContext.getMessagingService();
        _channel = messagingService.createChannel(_channelListener);
        _channel.sendInvitation("Let's play a game", "Chess App", 0);

    }

    private void onContactLeft(BBMPlatformContact contact) 
    {
        String goodbyeMsg = contact.getDisplayName() + " has left the game.";
        BBMPlatformData data = new BBMPlatformData(goodbyeMsg);

        try
        {
            _channel.sendData(data, _channel.getContactList());
        }
        catch (BBMPlatformException e) 
        {
           // Error handler code
        }
    }

    private BBMPlatformChannelListener _channelListener = new BBMPlatformChannelListener() 
    {
        public void contactsInvited(BBMPlatformConnection conn, BBMPlatformContactList contactList ) 
        {
        }
         
        public void contactsJoined(BBMPlatformConnection conn, BBMPlatformContactList contacts, String cookie,
         int type) 
        {
        }
        
        public void contactDeclined(BBMPlatformConnection conn, BBMPlatformContact contact) 
        {
        }
     
        public void contactLeft(BBMPlatformConnection conn, BBMPlatformContact contact) 
        {
            onContactLeft(contact);
        }
       
        public void dataReceived(BBMPlatformConnection conn, BBMPlatformContact sender, BBMPlatformData data) 
        {
        }
        
    };
}