title: About "SLComposeViewController" in iOS 11 beta
body: <p>In my project, I always use <code>SLComposeViewController</code> to share contents with third-party apps, but now, when I update my iPhone to iOS 11 beta, this no longer works.</p>
  
  <p>The <code>SLComposeViewControllerCompletionHandler</code> always callback <code>SLComposeViewControllerResultCancelled</code>.</p>
  
  <p>Why is this?</p>