title: I want to redraw a view
body: <p>I want to redraw a view.
  When I touch a button, my view have to redraw itself. (have to call viewWillAppear)</p>
  
  <p>But view's setNeedDisplay method doesn't redraw itself immediately.
  Because I have to redraw it immediately, the method is not suitable to me.</p>
  
  <p>I tried to remove all of viewController's view's subviews and to change viewController's
   view to other view.
  But these didn't work. (don't redraw)</p>
  
  <p>I need your help acutely.</p>
  
  <p>Thank you for your reading.</p>