导航栏右栏按钮项间距

Question

我创建了从情节串连图板，titleview的从码连续3个右边栏按钮项目添加了左边栏按钮项navigation bar http://oi61.tinypic.com/r0p8w4.jpg。

下面是代码：

override func viewDidLoad() {
    super.viewDidLoad()

    var screenWidth = UIScreen.mainScreen().bounds.width
    // custom title view
    var navBarWidth: CGFloat = self.navigationController!.navigationBar.frame.size.width
    let customTitleView = UIView(frame: CGRectMake(0, 0, navBarWidth, 44))
    titleLabel = UILabel(frame: CGRectMake(20, 0, navBarWidth, 40))
    titleLabel.text = conversationName
    if let titleFont = UIFont(name: "Roboto-Regular", size: 20) {
        titleLabel.font = titleFont
    }
    titleLabel.textColor = UIColor.whiteColor()

    customTitleView.addSubview(titleLabel)
    self.navigationItem.titleView = customTitleView

    // right bar buttons
    var searchImage = UIImage(named: "search")!
    var clipImage = UIImage(named: "clip")!
    var pencilImage = UIImage(named: "pencil")!

    var searchBtn = UIBarButtonItem(image: searchImage, style: UIBarButtonItemStyle.Plain, target: self, action: Selector("searchBtnPressed"))
    searchBtn.tintColor = UIColor.whiteColor()
    var clipBtn = UIBarButtonItem(image: clipImage, style: UIBarButtonItemStyle.Plain, target: self, action: Selector("clipBtnPressed"))
    clipBtn.tintColor = UIColor.whiteColor()
    var pencilBtn = UIBarButtonItem(image: pencilImage, style: UIBarButtonItemStyle.Plain, target: self, action: Selector("pencilBtnPressed"))
    pencilBtn.tintColor = UIColor.whiteColor()

    self.navigationItem.setRightBarButtonItems([pencilBtn, clipBtn, searchBtn], animated: false)
}

我的问题是，我想改变右按键之间的间距，但我不知道怎么办。

我试图在它们之间添加一个fixedButton但它只是增加了生存空间。

有人能帮我吗？谢谢。