1、問題背景

在研究使用IQKeyBoardManager來處理鍵盤的彈出和放下等一些列事件的時候，頁面使用的是UITableView，并在cell中繪制了多個文本輸入框。由于項(xiàng)目是基于UINavigationController建立的，當(dāng)鍵盤彈出時發(fā)現(xiàn)navigationBar 被自動隱藏了。等到鍵盤放下后navigationBar卻沒有像期望的那樣重新回到當(dāng)初的位置。第一感覺是不是使用了IQKeyBoardManager，而IQKeyBoardManager在處理鍵盤遮擋的時候更改了navigationbar的位置，照著這個想法隨便研究了一下IQKeyBoardManager。

2、IQKeyBoardManager 設(shè)計思想及加載過程

它繼承自NSObject，設(shè)計的方案是作為一個單例來加載，并且實(shí)現(xiàn)了NSObject 的類方法 load 來完成初始化，由于他采用的機(jī)制是將Manager作為鍵盤、設(shè)備方向相關(guān)事件的觀察者，并且基于響應(yīng)者當(dāng)前界面的響應(yīng)者鏈完成了相關(guān)控件的管理。

3、問題的最終確診及解決方案

各種嘗試更改IQKeyBoardManager在處理鍵盤彈出等事件相關(guān)方法都無果后，做了個移除IQKeyBoardManager的測試。結(jié)果發(fā)現(xiàn)navigationbar依然會被隱藏，經(jīng)過一陣眩暈后發(fā)現(xiàn)原來NavigationController的在IOS8之后新增了如下屬性，閑時還是得多讀書呀……

/// When the keyboard appears, the navigation controller's navigationBar toolbar will be hidden. The bars will remain hidden when the keyboard dismisses, but a tap in the content area will show them.
    @available(iOS 8.0, *)
    open var hidesBarsWhenKeyboardAppears: Bool

    /// When the user swipes, the navigation controller's navigationBar & toolbar will be hidden (on a swipe up) or shown (on a swipe down). The toolbar only participates if it has items.
    @available(iOS 8.0, *)
    open var hidesBarsOnSwipe: Bool

    /// When the UINavigationController's vertical size class is compact, hide the UINavigationBar and UIToolbar. Unhandled taps in the regions that would normally be occupied by these bars will reveal the bars.
    @available(iOS 8.0, *)
    open var hidesBarsWhenVerticallyCompact: Bool

    /// When the user taps, the navigation controller's navigationBar & toolbar will be hidden or shown, depending on the hidden state of the navigationBar. The toolbar will only be shown if it has items to display.
    @available(iOS 8.0, *)
    open var hidesBarsOnTap: Bool

看第一個屬性的注釋，內(nèi)心有一種放完炮就走的感覺，還好他留下了能解決問題的人，于是將希望寄托在了hidesBarsOnTap屬性上。
單純的通過在keyboard show和hidden時設(shè)置hidesBarsOnTap的true和false并沒有完美的解決我的問題。隨后增加了navigationbar顯示和隱藏的監(jiān)聽。
最終解決方案的代碼如下：

override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        self.navigationController?.isNavigationBarHidden = false
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardHidden(notify:)), name:NSNotification.Name.UIKeyboardDidHide , object:nil)
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardShow(notify:)), name:NSNotification.Name.UIKeyboardDidShow , object:nil)
        navigationController?.navigationBar.addObserver(self, forKeyPath: "hidden", options: NSKeyValueObservingOptions.new, context: nil)
    }
        
override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        navigationController?.hidesBarsWhenKeyboardAppears = false
        navigationController?.hidesBarsOnSwipe = false
        navigationController?.hidesBarsWhenVerticallyCompact = false
        navigationController?.hidesBarsOnTap = false        
    }
   
override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardDidHide, object: nil)
        NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardDidShow, object: nil)
        navigationController?.navigationBar.removeObserver(self, forKeyPath: "hidden", context: nil)
    }
    
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        
        if keyPath == "hidden",change != nil {
            let flag:Bool = change![NSKeyValueChangeKey.newKey] as! Bool
            if flag {
               self.navigationController?.hidesBarsOnTap = true
            }else{
               self.navigationController?.hidesBarsOnTap = false
            }
        }
        
    }
    
@objc func keyboardHidden(notify:Notification){
        
        self.navigationController?.hidesBarsOnTap =  navigationController?.isNavigationBarHidden == true ? true:false
    }
    
@objc func keyboardShow(notify:Notification){
        self.navigationController?.hidesBarsOnTap = true
    }

目前的解決方案還不是很完美，歡迎各位留言指正。