title: UIPickerView changed on iOS 11?
body: <p>On our app, we have a UIPickerView that lets you choose a season. However, on iOS 11, the <strong>Done</strong> button and <strong>Cancel</strong> button disappear and are only visible while switching between apps. Has anyone else experienced this? </p>
  
  <p>Screenshots of iOS 11 behavior, with iOS 10 behavior below. </p>
  
  <p>Edit: Here's a <a href="http://s000.tinyupload.com/?file_id=88468216267374189145" rel="nofollow noreferrer">complete sample app</a> with the issue: </p>
  
  <p>Here's the code for setting up the picker view</p>
  
  <pre><code>func setUpPickerView(){
  
      self.seasonPicker = UIPickerView.init(frame: CGRect.init(x: 0, y: 50, width: self.frame.width, height: UIScreen.main.bounds.height / 3))
      self.seasonPicker.delegate = self
      self.seasonPicker.dataSource = self
  
      self.seasonTextField.inputView = self.seasonPicker
  
      let toolbar = UIToolbar.init(frame: CGRect.init(x: 0, y: 0, width: self.frame.width, height: 50))
      toolbar.barStyle = UIBarStyle.default
  
      let labelTitle = UILabel.init(frame: CGRect.init(x: 0, y: 50, width: 150, height: 20))
      labelTitle.backgroundColor = UIColor.clear
      labelTitle.textColor = UIColor.black
      labelTitle.textAlignment = NSTextAlignment.left
      labelTitle.text = "Select a Season"
      labelTitle.sizeToFit()
  
      let typeFeild = UIBarButtonItem.init(customView: labelTitle)
      let cancelButton = UIBarButtonItem.init(title: "Cancel", style: UIBarButtonItemStyle.plain, target: self, action: #selector(didClickPickerCancel))
      let flexSpace = UIBarButtonItem.init(barButtonSystemItem: UIBarButtonSystemItem.flexibleSpace, target: nil, action: nil)
      let doneButton = UIBarButtonItem.init(title: "Done", style: UIBarButtonItemStyle.plain, target: self, action: #selector(didClickPickerDone))
      toolbar.items = [cancelButton, flexSpace, typeFeild, flexSpace, doneButton]
  
      toolbar.sizeToFit()
  
      self.seasonTextField.inputAccessoryView = toolbar
  
  }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/AWJSw.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AWJSw.jpg" alt="UIPickerView with missing done button"></a>
  <a href="https://i.stack.imgur.com/SEkww.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/SEkww.jpg" alt="UIPickerView&#39;s done button reappears while switching between views "></a>
  <a href="https://i.stack.imgur.com/R0LOR.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/R0LOR.png" alt="UIPickerView working as expected on iOS 10"></a></p>