超简单！！！ iOS设置状态栏、导航栏按钮、标题、颜色、透明度，

1. 要实现以下这些效果都非常简单

2. 废话不多说，先看看实现效果

3. 下面告诉你我为什么说实现这些效果非常简单

比如说要实现蚂蚁森林的导航栏效果(有以下几个需求)：

• 刚进入导航栏透明、两边按钮和文字都是白色、状态栏也是白色
• 向上滚动后导航栏背景由透明逐渐变成白色
• 当超过某一点后，标题变成黑色、状态栏变成黑色、两边按钮变成蓝色

实现步骤：
3.1. 实现刚进入导航栏透明、两边按钮和文字都是白色、状态栏也是白色

override func viewDidLoad()
{
    super.viewDidLoad()
    // 设置导航栏颜色为白色        
    navBarBarTintColor = .white
    // 设置刚进入页面时透明度为0
    navBarBackgroundAlpha = 0
}

3.2. 实现剩下两个需求

func scrollViewDidScroll(_ scrollView: UIScrollView)
{
    let offsetY = scrollView.contentOffset.y
    if (offsetY > NAVBAR_COLORCHANGE_POINT)
    {
        let alpha = (offsetY - NAVBAR_COLORCHANGE_POINT) / CGFloat(kNavBarBottom)
        // 向上滚动后导航栏背景由透明逐渐变成白色
        navBarBackgroundAlpha = alpha
        if (alpha > 0.5) {
            // 当超过某一点后，两边按钮变成蓝色
            navBarTintColor = UIColor(red: 0, green: 0.478431, blue: 1, alpha: 1.0)
            // 标题变成黑色
            navBarTitleColor = .black
            // 状态栏变成黑色
            statusBarStyle = .default
        } else {
            // 当没有超过某点，上面属性还原
            navBarTintColor = .white
            navBarTitleColor = .white
            statusBarStyle = .lightContent
        }
    }
    else
    {
        navBarBackgroundAlpha = 0
        navBarTintColor = .white
        navBarTitleColor = .white
        statusBarStyle = .lightContent
    }
}

3.3. 发现没有，改变相关属性只要一句代码就完全搞定了！！！

// 一行代码搞定导航栏颜色
navBarBarTintColor = .white
// 一行代码搞定导航栏透明度
navBarBackgroundAlpha = alpha
// 一行代码搞定导航栏两边按钮颜色
navBarTintColor = UIColor(red: 0, green: 0.478431, blue: 1, alpha: 1.0)
// 一行代码搞定导航栏上标题颜色
navBarTitleColor = .black
// 一行代码搞定状态栏是 default 还是 lightContent
statusBarStyle = .default

3.4. 说了这么多，看看几句代码能否实现我们需要的效果吧

3.5. 有人可能会问：这只是在一个界面里面，但是涉及到push、pop、右滑手势怎么办呢？
答：没关系，我已经给你处理好了，你不用写一句代码！！！那么看看效果吧

4. 好了，说了这么多接下来看看如何实现的吧

4.1 实现导航栏透明渐变就很简单了，网上一找一大堆，大部分都是通过加一层的方法来实现（在这里就是加一个view到navigationBar上）

// set navigationBar barTintColor
fileprivate func wr_setBackgroundColor(color:UIColor)
{
    if (backgroundView == nil)
    {
        // add a image(nil color) to _UIBarBackground make it clear
        setBackgroundImage(UIImage(), for: .default)
        backgroundView = UIView(frame: CGRect(x: 0, y: 0, width: Int(bounds.width), height: 64))
        // _UIBarBackground is first subView for navigationBar
        subviews.first?.insertSubview(backgroundView ?? UIView(), at: 0)
    }
    backgroundView?.backgroundColor = color
}

// set _UIBarBackground alpha (_UIBarBackground subviews alpha <= _UIBarBackground alpha)
fileprivate func wr_setBackgroundAlpha(alpha:CGFloat)
{
    let barBackgroundView = subviews[0]
    barBackgroundView.alpha = alpha
}

4.2 你以为就这样结束了吗，来看看下面的问题，当由透明的导航栏右滑到不透明的导航栏看看会出现什么情况？

4.3 处理右滑返回手势问题

我们都知道，导航栏是属于导航控制器的，一个导航栏不可能出现两个颜色，那么右滑突兀怎么解决呢？两个方法，一个方法是自定义导航栏（后面会说），另一个方法是改变导航栏颜色，我们假设当前控制器为fromVC，返回的控制器为toVC，如果可以实现从 fromVC 右滑到 toVC 导航栏颜色渐变那么问题就解决了！但是导航栏只有一个颜色啊~~~怎么办？
同样，可以通过加一层的方法来解决。我们可以记录一下 fromVC消失前对应的导航栏颜色 和 toVC 当前的导航栏颜色，然后根据右滑进度percentComplete，来计算渐变色，这样问题就解决了！

记录ViewController对应导航栏的颜色和透明度

// navigationBar barTintColor
var navBarBarTintColor: UIColor {
    get {
        guard let barTintColor = objc_getAssociatedObject(self, &AssociatedKeys.navBarBarTintColor) as? UIColor else {
            return UIColor.defaultNavBarBarTintColor
        }
        return barTintColor
    }
    set {
        objc_setAssociatedObject(self, &AssociatedKeys.navBarBarTintColor, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        
        if customNavBar.isKind(of: UINavigationBar.self) {
            let navBar = customNavBar as! UINavigationBar
            navBar.wr_setBackgroundColor(color: newValue)
        }
        else
        {
            if pushToCurrentVCFinished == true && pushToNextVCFinished == false {
                navigationController?.setNeedsNavigationBarUpdate(barTintColor: newValue)
            }
        }
    }
}

// navigationBar _UIBarBackground alpha
var navBarBackgroundAlpha:CGFloat {
    get {
        guard let barBackgroundAlpha = objc_getAssociatedObject(self, &AssociatedKeys.navBarBackgroundAlpha) as? CGFloat else {
            return 1.0
        }
        return barBackgroundAlpha
    }
    set {
        objc_setAssociatedObject(self, &AssociatedKeys.navBarBackgroundAlpha, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        
        if customNavBar.isKind(of: UINavigationBar.self) {
            let navBar = customNavBar as! UINavigationBar
            navBar.wr_setBackgroundAlpha(alpha: newValue)
        }
        else
        {
            if pushToCurrentVCFinished == true && pushToNextVCFinished == false {
                navigationController?.setNeedsNavigationBarUpdate(barBackgroundAlpha: newValue)
            }
        }
    }
}

交换系统方法 _updateInteractiveTransition（监控右滑返回手势的进度）

// swizzling system method: _updateInteractiveTransition
func wr_updateInteractiveTransition(_ percentComplete: CGFloat)
{
    guard let topViewController = topViewController,
        let coordinator       = topViewController.transitionCoordinator else {
            wr_updateInteractiveTransition(percentComplete)
            return
    }
    
    let fromVC = coordinator.viewController(forKey: .from)
    let toVC = coordinator.viewController(forKey: .to)
    updateNavigationBar(fromVC: fromVC, toVC: toVC, progress: percentComplete)
    
    wr_updateInteractiveTransition(percentComplete)
}

根据 fromVC 与 toVC 的导航栏颜色 配合 返回手势进度计算渐变色

// Calculate the middle Color with translation percent
class fileprivate func middleColor(fromColor: UIColor, toColor: UIColor, percent: CGFloat) -> UIColor
{
    // get current color RGBA
    var fromRed: CGFloat = 0
    var fromGreen: CGFloat = 0
    var fromBlue: CGFloat = 0
    var fromAlpha: CGFloat = 0
    fromColor.getRed(&fromRed, green: &fromGreen, blue: &fromBlue, alpha: &fromAlpha)
    
    // get to color RGBA
    var toRed: CGFloat = 0
    var toGreen: CGFloat = 0
    var toBlue: CGFloat = 0
    var toAlpha: CGFloat = 0
    toColor.getRed(&toRed, green: &toGreen, blue: &toBlue, alpha: &toAlpha)
    
    // calculate middle color RGBA
    let newRed = fromRed + (toRed - fromRed) * percent
    let newGreen = fromGreen + (toGreen - fromGreen) * percent
    let newBlue = fromBlue + (toBlue - fromBlue) * percent
    let newAlpha = fromAlpha + (toAlpha - fromAlpha) * percent
    return UIColor(red: newRed, green: newGreen, blue: newBlue, alpha: newAlpha)
}

改变导航栏颜色和透明度

fileprivate func updateNavigationBar(fromVC: UIViewController?, toVC: UIViewController?, progress: CGFloat)
{
    // change navBarBarTintColor
    let fromBarTintColor = fromVC?.navBarBarTintColor ?? .defaultNavBarBarTintColor
    let toBarTintColor   = toVC?.navBarBarTintColor ?? .defaultNavBarBarTintColor
    let newBarTintColor  = UIColor.middleColor(fromColor: fromBarTintColor, toColor: toBarTintColor, percent: progress)
    setNeedsNavigationBarUpdate(barTintColor: newBarTintColor)
    
    // change navBarTintColor
    let fromTintColor = fromVC?.navBarTintColor ?? .defaultNavBarTintColor
    let toTintColor = toVC?.navBarTintColor ?? .defaultNavBarTintColor
    let newTintColor = UIColor.middleColor(fromColor: fromTintColor, toColor: toTintColor, percent: progress)
    setNeedsNavigationBarUpdate(tintColor: newTintColor)
    
    // change navBarTitleColor
    let fromTitleColor = fromVC?.navBarTitleColor ?? .defaultNavBarTitleColor
    let toTitleColor = toVC?.navBarTitleColor ?? .defaultNavBarTitleColor
    let newTitleColor = UIColor.middleColor(fromColor: fromTitleColor, toColor: toTitleColor, percent: progress)
    setNeedsNavigationBarUpdate(titleColor: newTitleColor)
    
    // change navBar _UIBarBackground alpha
    let fromBarBackgroundAlpha = fromVC?.navBarBackgroundAlpha ?? UIColor.defaultBackgroundAlpha
    let toBarBackgroundAlpha = toVC?.navBarBackgroundAlpha ?? UIColor.defaultBackgroundAlpha
    let newBarBackgroundAlpha = UIColor.middleAlpha(fromAlpha: fromBarBackgroundAlpha, toAlpha: toBarBackgroundAlpha, percent: progress)
    setNeedsNavigationBarUpdate(barBackgroundAlpha: newBarBackgroundAlpha)
}

好了！来看看处理后的效果吧，是不是好多了呢~

4.4 别高兴的太早，还有其他问题。在右滑返回手势的过程中，导航栏颜色和透明度会根据手势变化而变化。但是一旦松手，系统会自动完成或取消返回操作。导致透明度停留在最后的那个状态。

4.5 咱们来处理右滑返回手势中断的问题吧~

通过遵守UINavigationBarDelegate协议，实现
optional public func navigationBar(_ navigationBar: UINavigationBar, shouldPop item: UINavigationItem) -> Bool // same as push methods 方法来监听右滑返回手势中断的情况

public func navigationBar(_ navigationBar: UINavigationBar, shouldPop item: UINavigationItem) -> Bool
{
    if let topVC = topViewController,
       let coor = topVC.transitionCoordinator, coor.initiallyInteractive {
        if #available(iOS 10.0, *) {
            coor.notifyWhenInteractionChanges({ (context) in
                self.dealInteractionChanges(context)
            })
        } else {
            coor.notifyWhenInteractionEnds({ (context) in
                self.dealInteractionChanges(context)
            })
        }
        return true
    }
    
    let itemCount = navigationBar.items?.count ?? 0
    let n = viewControllers.count >= itemCount ? 2 : 1
    let popToVC = viewControllers[viewControllers.count - n]
    
    popToViewController(popToVC, animated: true)
    return true
}

// deal the gesture of return break off
private func dealInteractionChanges(_ context: UIViewControllerTransitionCoordinatorContext)
{
    let animations: (UITransitionContextViewControllerKey) -> () = {
        let curColor = context.viewController(forKey: $0)?.navBarBarTintColor ?? UIColor.defaultNavBarBarTintColor
        let curAlpha = context.viewController(forKey: $0)?.navBarBackgroundAlpha ?? UIColor.defaultBackgroundAlpha
        
        self.setNeedsNavigationBarUpdate(barTintColor: curColor)
        self.setNeedsNavigationBarUpdate(barBackgroundAlpha: curAlpha)
    }
    
    // after that, cancel the gesture of return
    if context.isCancelled
    {
        let cancelDuration: TimeInterval = context.transitionDuration * Double(context.percentComplete)
        UIView.animate(withDuration: cancelDuration) {
            animations(.from)
        }
    }
    else
    {
        // after that, finish the gesture of return
        let finishDuration: TimeInterval = context.transitionDuration * Double(1 - context.percentComplete)
        UIView.animate(withDuration: finishDuration) {
            animations(.to)
        }
    }
}

处理后：

4.5 同样，push和pop也要处理一下 ~

但是push和pop我们拿不到进度怎么办呢？处理办法是，通过交换方法，自己实现给push和pop添加进度。

// MARK: swizzling push
struct pushProperties {
    fileprivate static let pushDuration = 0.13
    fileprivate static var displayCount = 0
    fileprivate static var pushProgress:CGFloat {
        let all:CGFloat = CGFloat(60.0 * pushDuration)
        let current = min(all, CGFloat(displayCount))
        return current / all
    }
}

// swizzling system method: pushViewController
func wr_pushViewController(_ viewController: UIViewController, animated: Bool)
{
    var displayLink:CADisplayLink? = CADisplayLink(target: self, selector: #selector(pushNeedDisplay))
    displayLink?.add(to: RunLoop.main, forMode: .defaultRunLoopMode)
    CATransaction.setCompletionBlock {
        displayLink?.invalidate()
        displayLink = nil
        pushProperties.displayCount = 0
        viewController.pushToCurrentVCFinished = true
    };
    CATransaction.setAnimationDuration(pushProperties.pushDuration)
    CATransaction.begin()
    wr_pushViewController(viewController, animated: animated)
    CATransaction.commit()
}

计算push进度，并且根据进度更新导航栏颜色和透明度

// change navigationBar barTintColor smooth before push to current VC finished or before pop to current VC finished
func pushNeedDisplay()
{
    guard let topViewController = topViewController,
          let coordinator       = topViewController.transitionCoordinator else {
            return
    }
    
    pushProperties.displayCount += 1
    let pushProgress = pushProperties.pushProgress
    // print("第\(pushProperties.displayCount)次push的进度：\(pushProgress)")
    let fromVC = coordinator.viewController(forKey: .from)
    let toVC = coordinator.viewController(forKey: .to)
    updateNavigationBar(fromVC: fromVC, toVC: toVC, progress: pushProgress)
}

pop的设置方法也一样，具体请查看代码 WRNavigationBar_swift

4.6 以上都是改变导航栏的颜色和透明度，同样改变导航栏的按钮颜色和标题颜色，以及状态栏状态都和改变颜色一样，每个ViewController记录一下。需要改变的时候，ViewController 改变一下属性就ok了，非常方便！

那么接下来看一下其他demo的动态效果图吧~~~

5. 好了，来说说前面提过的自定义导航栏吧

5.1 至于怎么自定义导航栏我就不说了，来说说如果是自定义导航栏，那怎么才能像之前一样一句代码改变导航栏属性。

经过封装，自定义导航栏只需要多写一行代码！！！

// 自定义导航栏必须设置这个属性!!!!!!
customNavBar = navBar

如果把这行代码放在基类控制器中，那么其他所有继承基类控制器都可以一句代码修改导航栏属性~~~
看看自定义导航栏的效果吧，是不是也很棒

6. 最后看一下移动导航栏的效果

实现代码

/// 设置导航栏在垂直方向上平移多少距离
func wr_setTranslationY(translationY:CGFloat)
{
    transform = CGAffineTransform.init(translationX: 0, y: translationY)
}

到这里就结束🌶，具体代码请前往：
https://github.com/wangrui460/WRNavigationBar
https://github.com/wangrui460/WRNavigationBar_swift

参考资料：
http://www.jianshu.com/p/640b64faea9a
http://www.jianshu.com/p/540a7e6f7b40
https://github.com/jawadasif/JNAPushPopCompletionBlock
http://www.jianshu.com/p/e3ca1b7b6cec
http://www.jianshu.com/p/454b06590cf1

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