 //设置界面
 extension HWBMainTabBarVC
 {
+    func setupComposeButton(){
+        tabBar.addSubview(composeButton)
+        //设置按钮的位置
+        let count = CGFloat(childViewControllers.count)
+        let w = tabBar.bounds.width / count
+        
+        composeButton.frame = tabBar.bounds.insetBy(dx: 2 * w, dy: 0)
+        
+    }
+    
     func setupChildController()
     {
         let array = [
             ["clsName":"HWBHomeViewController","title":"首页","imageName":"tabbar_home"],
             ["clsName":"HWBMessageViewController","title":"消息","imageName":"tabbar_message_center"],
+            ["clsName":"","title":"","imageName":""],
             ["clsName":"HWBDiscoverViewController","title":"发现","imageName":"tabbar_discover"],
             ["clsName":"HWBProfileViewController","title":"我的","imageName":"tabbar_profile"],
         

        // Dispose of any resources that can be recreated.
    }
    

}

//类似于OC中的分类，swift中切分代码，相近代码的函数放在一个extension便于代码维护

        super.viewDidLoad()

        setupChildController()
        setupComposeButton()
    }

    override func didReceiveMemoryWarning() {
