title: Keybord will not close after back from viewController in iOS 7.0
body: <p>I have one ViewController with custom view class.
  I have handled keyboard notification by adding into viewWillAppear method and remove notification in viewDidDisappear.</p>
  
  <p><strong>Notification adding into viewWillAppear:</strong></p>
  
  <pre><code>[[NSNotificationCenter defaultCenter] addObserver:self
                                           selector:@selector (keyboardWillShow:)
                                               name: UIKeyboardWillShowNotification object:nil];
  [[NSNotificationCenter defaultCenter] addObserver:self
                                           selector:@selector (keyboardWillHide)
                                               name: UIKeyboardWillHideNotification object:nil];
  
  [[NSNotificationCenter defaultCenter] addObserver:self
                                           selector:@selector (keyboardDidHide)
                                               name: UIKeyboardDidHideNotification object:nil];
  </code></pre>
  
  <p><strong>Remove Notification into viewDidDisappear:</strong></p>
  
  <pre><code>[[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object: nil];
  [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillHideNotification object: nil];
  [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardDidHideNotification object: nil];
  </code></pre>
  
  <p>and call view's method from viewController's notification method.</p>
  
  <p><strong>Issue:</strong></p>
  
  <ul>
  <li>After tapping on UITextField, keyboard appear and properly animation
  done</li>
  <li>But after keyboard appear, if user press back button from navigation-bar then keyboard will not remove after ViewController disappear from screen.</li>
  <li>Now user not able to close keyboard</li>
  </ul>
  
  <p>If I remove notification code then worked perfectly.</p>
  
  <p>Before iOS 7.0, its works perfectly with notification code. But in iOS 7.0, its not work.</p>
  
  <p>I have print NSLog in each notification method, in IOS 7.0 keyboardWillShow method executes at last and again keyboard appear. But in iOS 6.0, keyboardWillShow not execute at last.</p>
  
  <p>I have also implements UITextFieldDelegate methods.</p>
  
  <p>Thanks in advance</p>