title: Button and EditText check
body: <p>I have one EditText, TextView and one button. When i`m pressing it, textview updates by append(). But when i'm pressing this button in the next time, text adds again, updating my textview. How i can handle this? 
  Without something like:</p>
  
  <pre><code>btn.setClickable(false);
  </code></pre>
  
  <p>or</p>
  
  <pre><code>btn.setVisibility(View.GONE);
  </code></pre>
  
  <p>because if the text in the EditText field updates, button must work.</p>