// 聲明新的無標(biāo)題TabBarItem    
    let tabBarItem = UITabBarItem(title: nil, image: image, selectedImage: selectedImage)
    // 設(shè)置 tabBarItem 的 imageInsets 可以使圖標(biāo)居中顯示
    tabBarItem.imageInsets = UIEdgeInsetsMake(6, 0, -6, 0)

    viewController.tabBarItem = tabBarItem
}

// 用記錄下的frame建立一個(gè)UIView
let myView = UIView(frame: rect)
// 設(shè)置這個(gè)View的背景色
myView.backgroundColor = UIColor(patternImage: UIImage(named: "TabBarBG")!)
self.view.addSubview(myView)

for var i = 0; i < self.viewControllers?.count; i++ {

    let button = UIButton()

    // 根據(jù)子ViewController的個(gè)數(shù)計(jì)算Button的寬度
    let width = myView.frame.size.width / CGFloat(self.viewControllers!.count)
    let x = CGFloat(i) * width
    button.frame = CGRectMake(x, 0, width, myView.frame.size.height)

    // 設(shè)置Button未選中時(shí)候的圖標(biāo)
    let image = UIImage(named: "TabBar\(i)")?.imageWithRenderingMode(UIImageRenderingMode.AlwaysOriginal)
    button.setImage(image, forState: UIControlState.Normal)

    // 設(shè)置Button選中時(shí)候的圖標(biāo)，注意這里Button的狀態(tài)是Selected，而不是Highlighted
    let selImage = UIImage(named: "TabBar\(i)Sel")?.imageWithRenderingMode(UIImageRenderingMode.AlwaysOriginal)
    button.setImage(selImage, forState: UIControlState.Selected)

    // 設(shè)置Button未選中和選中時(shí)候的背景圖
    button.setBackgroundImage(UIImage(named: "TabBarBG"), forState: UIControlState.Normal)
    button.setBackgroundImage(UIImage(named: "TabBarBGSel"), forState: UIControlState.Selected)

    // 去掉UIButton自帶的高光效果
    button.adjustsImageWhenHighlighted = false

    myView.addSubview(button)

    // 設(shè)置UIButton的標(biāo)記
    button.tag = i

    button.addTarget(self, action: "onClick:", forControlEvents: UIControlEvents.TouchUpInside)

    // 設(shè)置默認(rèn)的選中項(xiàng)
    if i == 0 {
        button.selected = true
        self.selectButton = button
    }
}
    /**
    自定義Button的點(diǎn)擊事件

    :param: button
    */
    func onClick(button: UIButton) {
        // 將上個(gè)選中按鈕設(shè)置為未選中
        self.selectButton.selected = false
        // 當(dāng)前按鈕設(shè)置為選中
        button.selected = true
        // 記錄選中按鈕
        self.selectButton = button

        // 通過UITabBarController的selectedIndex屬性設(shè)置選中了哪個(gè)UIViewController
        self.selectedIndex = button.tag
    }

// 用來記錄當(dāng)前選中按鈕
private var currentSelectedButton = UIButton()
// 用來指示選中的背景
private var selectionIndicatorImageView: UIImageView!
// 單個(gè)item的寬度
private var itemWidth: CGFloat!
在viewDidLoad()方法中加入以下代碼：

override func viewDidLoad() {
    super.viewDidLoad()

    // 記錄TabBarController自帶TabBar的位置
    let rect = self.tabBar.frame
    // 移除TabBarController自帶的TabBar
    self.tabBar.removeFromSuperview()

    // 自定義TabBar的背景
    let backgroundView = UIView(frame: rect)
    backgroundView.backgroundColor = UIColor(patternImage: UIImage(named: "TabBarBG")!)

    self.view.addSubview(backgroundView)

    itemWidth = backgroundView.frame.size.width / CGFloat(self.viewControllers!.count)

    selectionIndicatorImageView = UIImageView(frame: CGRectMake(0, 0, itemWidth, backgroundView.frame.size.height))
    selectionIndicatorImageView.image = UIImage(named: "TabBarBGSel")

    backgroundView.addSubview(selectionIndicatorImageView)

    for var i = 0; i < viewControllers!.count; i++ {

        let button = CGMTabBarButton(frame: CGRectMake(itemWidth * CGFloat(i), 0, itemWidth, backgroundView.frame.size.height))

        let image = UIImage(named: "TabBar\(i)")!
        let selImage = UIImage(named: "TabBar\(i)Sel")!

        button.setImage(image, forState: UIControlState.Normal)
        button.setImage(selImage, forState: UIControlState.Selected)

        button.addTarget(self, action: "onClick:", forControlEvents: UIControlEvents.TouchUpInside)

        button.tag = i

        // 去掉buttond的高光效果
        button.adjustsImageWhenHighlighted = false

        backgroundView.addSubview(button)
    }             
}

func onClick(button: UIButton) {
    // 將上個(gè)選中俺就設(shè)置為為選中
    self.currentSelectedButton.selected = false
    // 當(dāng)前按鈕設(shè)置為選中
    button.selected = true

    self.currentSelectedButton = button

    let x = CGFloat(button.tag) + 0.5

    // 為TabBarItem的背景添加動(dòng)畫
    UIView.animateWithDuration(0.4, delay: 0.0, usingSpringWithDamping: 0.7, initialSpringVelocity: 10.0, options: UIViewAnimationOptions.CurveEaseInOut, animations: { () -> Void in

        self.selectionIndicatorImageView.center.x = self.itemWidth * x

        }, completion: nil)

    self.selectedIndex = button.tag
}