Build a multi-user collaboration android app
<p>Greetings to all SO developers!</p>

<p>I was searching for a way to allow collaboration on one activity of an android app. My problem is as follows: 
Lets say I have a simple android application having a EditText field in it. All users who have this app installed, are stored in my database. One user opens the app on his phone.</p>

<p><strong>What I want is: That he can add another user to his own screen(activity) and they both can write in the EditText field together in real-time.</strong></p>

<p>Edit: Also, what if I want the users to be on the same android canvas(like in a drawing app)?</p>

<p>So, for one, how do I implement this functionality of adding another user(say User2) to User1's activity, and for two, they should be able to write in the editText field together. </p>

<p>Any help/samples/resources would be appreciated, as I did search over the internet and on StackOverflow too, but didn't exactly found what I was looking for. </p>
