title: get black screen when switch view controller with XCode storyboard
body: <p>I am writing a simple app with a tab bar controller, and two tabs. The first tab will switch to another UITableViewController, which works fine. The second tab should switch to a view controller, which inherits from UIViewController, but it just shows black screen. </p>
  
  <p>And I hook on ViewDidLoad, ViewDidAppear functions in the destination UIViewController, I found it is loaded well. But it just shows me a black screen. Any idea of what happen here? And how to fix it?</p>