title: TextField is not pushed up smoothly by keyboard, like in Whatsapp and Hangouts
body: <p>I'm trying to mimic the <code>UITextField</code>-keyboard relation in Whatsapp app.
  As most of you know, there is a fixed <code>UITextField</code> at the bottom of the screen and keyboard comes up as you tap the <code>UITextField</code>. While keyboard is coming up, <code>UITextField</code> stick to the keyboard and they slide together very smoothly.</p>
  
  <p>Read Apple's documentation pages which is about moving views under the keyboard several times.</p>
  
  <p><strong><em>What I have tried so far:</em></strong></p>
  
  <ul>
  <li><p><strong>Listened to keyboard notifications</strong>. I used both <code>setFrame:</code> and <code>setContentOffset:animated:</code> method within animation block. Didn't work as good as expected. The <code>UIViewAnimationCurve</code> value that keyboard animation has is 7, I couldn't find what it means as <code>UIViewAnimationCurve</code> has only 4 integer enum type. I think animation curve of keyboard animation is not provided to developers, I hope I'm wrong.</p></li>
  <li><p><strong>Using custom inputAccessoryView with lower z-index value</strong>. I had two exact <code>UIViews</code>, one is fixed at the bottom and the other is custom <code>inputAccessoryView</code> that was going to hide beneath the fixed one since it has lower <code>zPosition</code> value. Therefore, user wasn't going to see the <code>inputAccessoryView</code> was coming up from outside of the screen but fixed view was being pushed up by keyboard. But no use, again. Changing <code>zPosition</code> value does not change anything.</p></li>
  </ul>
  
  <p>At last, I thought Whatsapp might not be using system keyboard but a custom one. But if this is the case, it is a very very bad choice of design so that option is eliminated.</p>
  
  <p>Anyone has an idea of how Whatsapp (or Hangouts) implemented that?</p>