// Override point for customization after application launch.

        //初始化window， 大小为设备物理大小

        self.window = UIWindow(frame: UIScreen.mainScreen().bounds)

        //把window的背景颜色改成白色

        self.window?.backgroundColor = UIColor.whiteColor()

        //让window作为主window显示

        self.window?.makeKeyAndVisible()

        /*-----------------初始化Tabbar控制器--------------*/

        let home = UIViewController()

        let message = UIViewController()

        let search = UIViewController()

        let setting = UIViewController()

        let viewControllers = [home, message, search, setting]

        let tabbarCtrl = UITabBarController()

        tabbarCtrl.viewControllers = viewControllers

        self.window?.rootViewController = tabbarCtrl

        //创建UITabBarItem

        //使用系统的样式创建

        let tabItem1 = UITabBarItem(tabBarSystemItem: UITabBarSystemItem.Favorites, tag: 1)

        home.tabBarItem = tabItem1

        let tabItem2 = UITabBarItem(tabBarSystemItem: UITabBarSystemItem.Bookmarks, tag: 1)

        message.tabBarItem = tabItem2

        //使用自定义的图片、标题

        let tabItem3 = UITabBarItem(title: "搜索", image: UIImage(named: "tabbar_discover_highlighted.png"), tag: 1)

        search.tabBarItem = tabItem3

        let tabItem4 = UITabBarItem(title: "设置", image: UIImage(named: "tabbar_profile_highlighted.png"), tag: 1)

        setting.tabBarItem = tabItem4

        /*------------------设置tabbar工具栏------------------*/

        let tabbar = tabbarCtrl.tabBar

        //设置tabBar的背景图片

        var img = UIImage(named: "navbg.png")

        UIGraphicsBeginImageContext(CGSizeMake(width, 49))

        img?.drawInRect(CGRectMake(0, 0, width, 49))

        img = UIGraphicsGetImageFromCurrentImageContext()

        UIGraphicsEndImageContext()

        tabbar.backgroundImage = img

        //设置tabBar的选中图片颜色

        tabbar.tintColor = UIColor.redColor()

        //设置选中item后，盖在此item上的图片

        tabbar.selectionIndicatorImage = UIImage(named: "选中.png")

        //为item是指一个小图标

        tabItem1.badgeValue = "New";