SearchBar Flash when it added with left item

[vzheng56]

var searchBar = UISearchBar()
searchBar.delegate = self
searchBar.searchBarStyle = UISearchBarStyle.Default
//self.navigationItem.titleView = searchBar
self.rbsl_targetViewController().navigationItem.titleView = searchBar

var view = UIView(frame: CGRectMake(0, 0, 100, 30))
view.backgroundColor = UIColor.blackColor()
var leftView = UIBarButtonItem(customView: view)
self.rbsl_storyboardLink().navigationItem.leftBarButtonItem = leftView

[vzheng56]

rightBarButtonItem is not