我想创建一个动画，例如 iOS 应用 facebook at tabswitch^[1]。我已经尝试开发某种动画，出现的问题是旧 View Controller 直接在开关上变得不可见，而不是在新 Controller 快速滑入时慢慢淡出。

我发现了这个 SO 问题 How to animate Tab bar tab switch with a CrossDissolve slide transition?但是正确标记的解决方案对我来说并不适用(它不是幻灯片，它是淡入淡出的过渡)。我还想得到的是向左或向右滑动以切换选项卡的功能。就像在旧版 Facebook 上一样。

到目前为止我得到的是:

extension TabBarController: UITabBarControllerDelegate  {
    func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {
        guard let fromView = selectedViewController?.view,
              let toView = viewController.view else { return false }
        if fromView != toView {
            toView.transform = CGAffineTransform(translationX: -90, y: 0)
            UIView.animate(withDuration: 0.25, delay: 0.0, options: .curveEaseInOut, animations: {
                toView.transform = CGAffineTransform(translationX: 0, y: 0)
            })
        }; return true
    }
}

class TabBarController: UITabBarController {
    override func viewDidLoad() {
        super.viewDidLoad()
        delegate = self
    }
}

如何解决这个问题？

^[1] 我非常想从 Facebook 应用程序添加 gif。问题是我不想审查视频，只是想透露太多我的数据。 (即使 fb 已经有了它们)。同样在 youtube 上我没有找到合适的录音。请在 iOS 的 fb 应用程序中自己尝试。

最佳答案

您可以使用以下思路:https://samwize.com/2016/04/27/making-tab-bar-slide-when-selected/

此外，这里是更新到 Swift 4.1 的代码，我还删除了强制展开:

import UIKit

class MyTabBarController: UITabBarController {

    override func viewDidLoad() {
        super.viewDidLoad()

        delegate = self
    }
}

extension MyTabBarController: UITabBarControllerDelegate  {
    func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {
        guard let tabViewControllers = tabBarController.viewControllers, let toIndex = tabViewControllers.index(of: viewController) else {
            return false
        }
        animateToTab(toIndex: toIndex)
        return true
    }

    func animateToTab(toIndex: Int) {
        guard let tabViewControllers = viewControllers,
            let selectedVC = selectedViewController else { return }

        guard let fromView = selectedVC.view,
            let toView = tabViewControllers[toIndex].view,
            let fromIndex = tabViewControllers.index(of: selectedVC),
            fromIndex != toIndex else { return }


        // Add the toView to the tab bar view
        fromView.superview?.addSubview(toView)

        // Position toView off screen (to the left/right of fromView)
        let screenWidth = UIScreen.main.bounds.size.width
        let scrollRight = toIndex > fromIndex
        let offset = (scrollRight ? screenWidth : -screenWidth)
        toView.center = CGPoint(x: fromView.center.x + offset, y: toView.center.y)

        // Disable interaction during animation
        view.isUserInteractionEnabled = false

        UIView.animate(withDuration: 0.3,
                       delay: 0.0,
                       usingSpringWithDamping: 1,
                       initialSpringVelocity: 0,
                       options: .curveEaseOut,
                       animations: {
                        // Slide the views by -offset
                        fromView.center = CGPoint(x: fromView.center.x - offset, y: fromView.center.y)
                        toView.center = CGPoint(x: toView.center.x - offset, y: toView.center.y)

        }, completion: { finished in
            // Remove the old view from the tabbar view.
            fromView.removeFromSuperview()
            self.selectedIndex = toIndex
            self.view.isUserInteractionEnabled = true
        })
    }
}

因此，您需要子类化 UITabBarController 并且您还必须编写动画部分，您可以调整动画选项(延迟、持续时间等)。

希望对你有帮助，干杯!

关于swift - ViewController 滑动动画，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/51482618/