修改UINavigationBar 类

var item:UINavigationItem = UINavigationItem();

var viewTitle = UIView();

viewTitle.backgroundColor = UIColor.redColor();

viewTitle.frame = CGRectMake(0, 0, 20, 30)

item.titleView = viewTitle;

var button:UIBarButtonItem = UIBarButtonItem(title: "Left_1", style: UIBarButtonItemStyle.Done, target: nil, action: "aaa");

var button2:UIBarButtonItem = UIBarButtonItem(title: "Left_2", style: UIBarButtonItemStyle.Done, target: nil, action: "aaa");

var button3:UIBarButtonItem = UIBarButtonItem(title: "Right_1", style: UIBarButtonItemStyle.Done, target: nil, action: "aaa");

var button4:UIBarButtonItem = UIBarButtonItem(title: "Right_2", style: UIBarButtonItemStyle.Done, target: nil, action: "aaa");

item.leftBarButtonItems = [button,button2]

item.rightBarButtonItems = [button3,button4]

nav.pushNavigationItem(item, animated: true);