title: How to check existing user in cognito - android?
body: <p>so i have aws cognito set up in android. And i want to perform a check to see when the user enters a username, that that username doesn't already exist in my cognito pool.</p>
  
  <p>Currently i have this:</p>
  
  <pre><code> cognitoUser = userPool.getUser(username_ET.getText().toString());
   if(cognitoUser.getUserId().isEmpty())
   {
        //Great, this is a new user.
   }
  </code></pre>
  
  <p>But, cognitoUser just gets set to whatever i put in, it doesn't go back in check.</p>
  
  <p>Hope someone can help!</p>