iOS10中的动画导航栏barTintColor更改不起作用

Question

我升级到XCode 8.0 / iOS 10，现在我的导航栏的颜色变化动画不再起作用了，它直接改变颜色，没有任何动画。

UIView.animateWithDuration(0.2, animations: {
    self.navigationController?.navigationBar.barTintColor = currentSection.color!
})

有人知道如何解决这个问题吗？

Answer 1

要在iOS10中为导航栏的颜色变化设置动画，你需要在动画块内设置颜色后调用layoutIfNeeded。

示例代码：

UIView.animateWithDuration(0.5) { 
    self.navigationController?.navigationBar.barTintColor = UIColor.redColor()
    self.navigationController?.navigationBar.layoutIfNeeded()
}

我还想通知 Apple doesn’t officialy support 动画在 barTintColor 等属性中，以便该方法可以随时中断。

如果在动画过程中在导航栏上调用 -layoutIfNeeded 块它应该更新其背景属性，但鉴于性质 这些属性的作用，真的从来没有任何一种 保证您可以为其中任何一个设置动画。

Answer 2

互动动画

定义一个协议：

/// Navigation bar colors for `ColorableNavigationController`, called on `push` & `pop` actions
public protocol NavigationBarColorable: UIViewController {
    var navigationTintColor: UIColor? { get }
    var navigationBarTintColor: UIColor? { get }
}

public extension NavigationBarColorable {
    var navigationTintColor: UIColor? { return nil }
}

定义一个自定义的NavigationController 子类：

class AppNavigationController: UINavigationController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        navigationBar.shadowImage = UIImage()
        if let colors = rootViewController as? NavigationBarColorable {
            setNavigationBarColors(colors)            
        }
    }
    
    private var previousViewController: UIViewController? {
        guard viewControllers.count > 1 else {
            return nil
        }
        return viewControllers[viewControllers.count - 2]
    }
    
    override open func pushViewController(_ viewController: UIViewController, animated: Bool) {
        if let colors = viewController as? NavigationBarColorable {
            setNavigationBarColors(colors)
        }
               
        super.pushViewController(viewController, animated: animated)
    }
    
    override open func popViewController(animated: Bool) -> UIViewController? {
        if let colors = previousViewController as? NavigationBarColorable {
            setNavigationBarColors(colors)
        }
                        
        // Let's start pop action or we can't get transitionCoordinator()
        let popViewController = super.popViewController(animated: animated)
        
        // Secure situation if user cancelled transition
        transitionCoordinator?.animate(alongsideTransition: nil, completion: { [weak self] context in
            guard let `self` = self else { return }

            guard let colors = self.topViewController as? NavigationBarColorable else { return }
            self.setNavigationBarColors(colors)
        })
        
        return popViewController
    }
    
    override func popToRootViewController(animated: Bool) -> [UIViewController]? {
        if let colors = rootViewController as? NavigationBarColorable {
            setNavigationBarColors(colors)
        }
        
        let controllers = super.popToRootViewController(animated: animated)
        
        return controllers
    }
    
    private func setNavigationBarColors(_ colors: NavigationBarColorable) {
        
        if let tintColor = colors.navigationTintColor {
            navigationBar.titleTextAttributes = [
                .foregroundColor : tintColor
            ]
            navigationBar.tintColor = tintColor
        }
        
        navigationBar.barTintColor = colors.navigationBarTintColor
    }
}

现在您可以在AppNavigationController 内的任何控制器中符合NavigationBarColorable 并为其赋予任何您想要的颜色。

extension FirstViewController: NavigationBarColorable {
    public var navigationBarTintColor: UIColor? { UIColor.red }
    public var navigationTintColor: UIColor? { UIColor.white }
}

extension SecondViewController: NavigationBarColorable {
    public var navigationBarTintColor: UIColor? { UIColor.blue }
    public var navigationTintColor: UIColor? { UIColor.orange }
}

别忘了实现这个有用的扩展：

extension UINavigationController {
    var rootViewController: UIViewController? {
        return viewControllers.first
    }
}