1. UINavigationController管理一個(gè)VC的棧，棧底的VC叫做這個(gè)UINavigationController的root view controller.
2. 有一個(gè)函數(shù)叫做popToRootViewController(animated:)，就是返回rootVC如暖。
3. UINavigationController在頂部有一個(gè)navigationBar擅憔，繼承自UIView。它的frame衡怀，bound及alpha值都不能改變。隱藏或者顯示這個(gè)navigationBar要調(diào)用UINavigationController的setNavigationBarHidden(_:animated:)方法。其中動(dòng)畫(huà)的時(shí)間是一個(gè)常量UINavigationControllerHideShowBarDuration嗽元，不能改變。

To show or hide the navigation bar, you should always do so through the navigation controller by changing its isNavigationBarHidden property or calling the setNavigationBarHidden(_:animated:) method.

              self.navigationController?.setNavigationBarHidden(false, animated: true)
              self.navigationController?.navigationBarHidden

4. navigationBar的各個(gè)屬性

   
   
   NavBar的各個(gè)屬性

5. navigationBar的背景色

self.navigationController?.navigationBar.barTintColor = UIColor.yellowColor()

背景色

6. navigationBar的配置
   navigationBar有左喂击、中剂癌、右三個(gè)部分。顯示的具體內(nèi)容是根據(jù)當(dāng)前VC的UINavigationItem屬性及棧中前一個(gè)VC的UINavigationItem屬性配置的翰绊。
7. UINavigationItem
   UINavigationItem作為VC的屬性佩谷，在這個(gè)VC處于navigation stack時(shí)，用來(lái)設(shè)置定于導(dǎo)航條的樣式等等监嗜。屬性分別用來(lái)設(shè)置導(dǎo)航條左谐檀、中、右的樣式等裁奇。

• 左邊
  • leftBarButtonItem 最左邊的按鈕
  • leftBarButtonItems 最左邊的按鈕們（可以有多個(gè)）
  • setLeftBarButtonItems(_:animated:)

    self.navigationItem.leftBarButtonItem = UIBarButtonItem.init(title: "left", style: .Plain, target: self, action: #selector(TGVCButtom.leftButtonClicked(_:)))
    self.navigationItem.leftBarButtonItem?.tintColor = UIColor.brownColor()
    let dict = [NSForegroundColorAttributeName : UIColor.blueColor(),
                NSKernAttributeName: NSNumber.init(int: 10) 
    self.navigationItem.leftBarButtonItem?.setTitleTextAttributes(dict, forState: .Normal)
  
    let sencondleftBarButtonItem = UIBarButtonItem.init(title: "leftSecond", style: .Plain, target: self, action: #selector(TGVCButtom.secondLeftButtonClicked(_:)))  
  

self.navigationItem.setLeftBarButtonItems([self.navigationItem.leftBarButtonItem!,sencondleftBarButtonItem], animated: true)
```

左邊的按鈕們

• 中間
• title

     self.navigationItem.title = "buttomVC"

- titleView  會(huì)覆蓋title桐猬。如果需要設(shè)置button、富文本可以考慮這個(gè)
> Custom title views are centered on the navigation bar and may be resized to fit
  ```
    self.navigationItem.titleView = UIImageView.init(image: TGResizeImage(UIImage.init(named: "cat"), byRatio: 0.5) )
  ```

• 右邊刽肠。和左邊類似溃肪。
• rightBarButtonItem
• rightBarButtonItems
• setRightBarButtonItems(_:animated:)

• 返回按鈕
  有時(shí)候既要有一個(gè)返回的按鈕，又要有一個(gè)左邊的按鈕音五。達(dá)到微信的網(wǎng)頁(yè)常有的返回+關(guān)閉的效果乍惊。

  
  
  返回+關(guān)閉
  
  

  假設(shè)一個(gè)當(dāng)前VC是A，push一個(gè)VC出去放仗。

        self.navigationController?.pushViewController(self.topVC, animated:true)

那么需要
1. 設(shè)置自己的backBarButtonItem

       self.navigationItem.backBarButtonItem = UIBarButtonItem.init(title: "back", style: .Plain, target: nil, action: nil);

2. 設(shè)置topVC的leftBarButtonItem

        self.navigationItem.leftBarButtonItem = UIBarButtonItem.init(title: "leftButton", style: .Done, target: self, action: nil)

3. 設(shè)置topVC的兩個(gè)變量

        self.navigationItem.hidesBackButton = false //返回按鈕沒(méi)有被隱藏
        self.navigationItem.leftItemsSupplementBackButton = true //返回按鈕可以和左邊的按鈕一起出現(xiàn)

返回+關(guān)閉

8. 奇怪的prompt

A single line of text displayed at the top of the navigation bar

        self.navigationItem.prompt = "promt"http://不知道干嘛的润绎。。有啥用呢

奇怪的prompt

9. 一個(gè)解釋
   
10. 如何禁止左滑返回

self.navigationController?.interactivePopGestureRecognizer?.enabled = false