Question

我正在尝试在UITabBarController上创建一个过渡效果，有点类似于Facebook应用。我设法得到一个“滚动效果”工作在制表符切换，但我似乎无法弄清楚如何交叉溶解（或它至少不起作用）。

这是我目前的代码：

import UIKit

class ScrollingTabBarControllerDelegate: NSObject, UITabBarControllerDelegate {
    func tabBarController(_ tabBarController: UITabBarController, animationControllerForTransitionFrom fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {

        return ScrollingTransitionAnimator(tabBarController: tabBarController, lastIndex: tabBarController.selectedIndex)
    }
}

class ScrollingTransitionAnimator: NSObject, UIViewControllerAnimatedTransitioning {
    weak var transitionContext: UIViewControllerContextTransitioning?
    var tabBarController: UITabBarController!
    var lastIndex = 0

    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.2
    }

    init(tabBarController: UITabBarController, lastIndex: Int) {
        self.tabBarController = tabBarController
        self.lastIndex = lastIndex
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        self.transitionContext = transitionContext

        let containerView = transitionContext.containerView
        let fromViewController = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from)
        let toViewController = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to)

        containerView.addSubview(toViewController!.view)

        var viewWidth = toViewController!.view.bounds.width

        if tabBarController.selectedIndex < lastIndex {
            viewWidth = -viewWidth
        }

        toViewController!.view.transform = CGAffineTransform(translationX: viewWidth, y: 0)

        UIView.animate(withDuration: self.transitionDuration(using: (self.transitionContext)), delay: 0.0, usingSpringWithDamping: 1.2, initialSpringVelocity: 2.5, options: .transitionCrossDissolve, animations: {
            toViewController!.view.transform = CGAffineTransform.identity
            fromViewController!.view.transform = CGAffineTransform(translationX: -viewWidth, y: 0)
        }, completion: { _ in
            self.transitionContext?.completeTransition(!self.transitionContext!.transitionWasCancelled)
            fromViewController!.view.transform = CGAffineTransform.identity
        })
    }
}

如果有人知道如何让它发挥作用会很好，现在已经尝试了好几天没有进展......：/

编辑：我通过将UIView.animate块替换为：

进行交叉解散工作

UIView.transition(with: containerView, duration: 0.2, options: .transitionCrossDissolve, animations: {

    toViewController!.view.transform = CGAffineTransform.identity
    fromViewController!.view.transform = CGAffineTransform(translationX: -viewWidth, y: 0)

}, completion: { _ in

    self.transitionContext?.completeTransition(!self.transitionContext!.transitionWasCancelled)
    fromViewController!.view.transform = CGAffineTransform.identity

})

然而，动画非常滞后且无法使用：（

编辑2 ：对于尝试使用这些代码段的人，请不要忘记为UITabBarController连接代理，否则不会发生任何事情。

编辑3：我找到了一个完全符合我要求的Swift库： https://github.com/Interactive-Studio/TransitionableTab

Answer 1

有一种更简单的方法可以做到这一点。在tabbar委托中添加以下代码：

使用Swift 2,3和4

class MySubclassedTabBarController: UITabBarController {

    override func viewDidLoad() {
      super.viewDidLoad()
      delegate = self
    }
}

extension MySubclassedTabBarController: UITabBarControllerDelegate  {
    func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {

        guard let fromView = selectedViewController?.view, let toView = viewController.view else {
          return false // Make sure you want this as false
        }

        if fromView != toView {
          UIView.transition(from: fromView, to: toView, duration: 0.3, options: [.transitionCrossDissolve], completion: nil)
        }

        return true
    }
}

编辑（4/23/18） 由于这个答案越来越受欢迎，我更新了代码以删除强制解包，这是一种不好的做法，并添加了保护声明。

编辑（7/11/18） @AlbertoGarcía是对的。如果您点击两次标签栏图标，则会出现空白屏幕。所以我加了一个额外的支票

Answer 2

如果您想使用UIViewControllerAnimatedTransitioning进行比UIView.transition更自定义的操作，请查看this gist。

// MyTabController.swift

import UIKit

class MyTabBarController: UITabBarController {

    override func viewDidLoad() {
        super.viewDidLoad()
        delegate = self
    }
}

extension MyTabBarController: UITabBarControllerDelegate {

    func tabBarController(_ tabBarController: UITabBarController, animationControllerForTransitionFrom fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return MyTransition(viewControllers: tabBarController.viewControllers)
    }
}

class MyTransition: NSObject, UIViewControllerAnimatedTransitioning {

    let viewControllers: [UIViewController]?
    let transitionDuration: Double = 1

    init(viewControllers: [UIViewController]?) {
        self.viewControllers = viewControllers
    }

    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return TimeInterval(transitionDuration)
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {

        guard
            let fromVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from),
            let fromView = fromVC.view,
            let fromIndex = getIndex(forViewController: fromVC),
            let toVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to),
            let toView = toVC.view,
            let toIndex = getIndex(forViewController: toVC)
            else {
                transitionContext.completeTransition(false)
                return
        }

        let frame = transitionContext.initialFrame(for: fromVC)
        var fromFrameEnd = frame
        var toFrameStart = frame
        fromFrameEnd.origin.x = toIndex > fromIndex ? frame.origin.x - frame.width : frame.origin.x + frame.width
        toFrameStart.origin.x = toIndex > fromIndex ? frame.origin.x + frame.width : frame.origin.x - frame.width
        toView.frame = toFrameStart

        DispatchQueue.main.async {
            transitionContext.containerView.addSubview(toView)
            UIView.animate(withDuration: self.transitionDuration, animations: {
                fromView.frame = fromFrameEnd
                toView.frame = frame
            }, completion: {success in
                fromView.removeFromSuperview()
                transitionContext.completeTransition(success)
            })
        }
    }

    func getIndex(forViewController vc: UIViewController) -> Int? {
        guard let vcs = self.viewControllers else { return nil }
        for (index, thisVC) in vcs.enumerated() {
            if thisVC == vc { return index }
        }
        return nil
    }
}

Answer 3

我在用户点击和以编程方式调用selectedIndex = X时都无法使用制表符栏动画，因为在以编程方式设置选定的制表符时，可接受的解决方案对我不起作用。

最后，我设法通过UITabBarControllerDelegate和自定义UIViewControllerAnimatedTransitioning来解决它，如下所示：

extension MainController: UITabBarControllerDelegate {

    public func tabBarController(
            _ tabBarController: UITabBarController,
            animationControllerForTransitionFrom fromVC: UIViewController,
            to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return FadePushAnimator()
    }
}

FadePushAnimator的外观如下：

class FadePushAnimator: NSObject, UIViewControllerAnimatedTransitioning {

    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.3
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        guard
                let toViewController = transitionContext.viewController(forKey: .to)
                else {
            return
        }

        transitionContext.containerView.addSubview(toViewController.view)
        toViewController.view.alpha = 0

        let duration = self.transitionDuration(using: transitionContext)
        UIView.animate(withDuration: duration, animations: {
            toViewController.view.alpha = 1
        }, completion: { _ in
            transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
        })

    }
}

此方法支持任何类型的自定义动画，并且可以在用户点击时以编程方式设置选定的选项卡。 在Swift 5上进行了测试。

Answer 4

所以，几年后，我有了更多的经验，在对相同的行为重新审视了自己的问题之后，我对德里克的回答有所改善。

我继承了他的大部分代码（这似乎是最好的解决方案）。

我更改了

我通过添加toCoverView和fromCoverView向幻灯片动画添加了一个crossDissolve动画（如我最初想要的），这些是另一个视图的快照视图，用于同时淡入/淡出。
已将帧宽度更改为已经从75％开始，而不必转换整个100％宽度，现在仅转换25％，这使它变得更加生动。
添加了SpringWithDamping和初始SpringVelocity设置。

这些变化使我感觉与Facebook的实现几乎一样，我个人对此非常满意。

这是适应的答案（大部分功劳归于德里克，所以一定要投票给他）：

class MyTabBarController: UITabBarController {

    override func viewDidLoad() {
        super.viewDidLoad()
        delegate = self
    }
}

extension MyTabBarController: UITabBarControllerDelegate {

    func tabBarController(_ tabBarController: UITabBarController, animationControllerForTransitionFrom fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return MyTransition(viewControllers: tabBarController.viewControllers)
    }
}

class MyTransition: NSObject, UIViewControllerAnimatedTransitioning {

    let viewControllers: [UIViewController]?
    let transitionDuration: Double = 0.2

    init(viewControllers: [UIViewController]?) {
        self.viewControllers = viewControllers
    }

    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return TimeInterval(transitionDuration)
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {

        guard
            let fromVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from),
            let fromView = fromVC.view,
            let fromIndex = getIndex(forViewController: fromVC),
            let toVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to),
            let toView = toVC.view,
            let toIndex = getIndex(forViewController: toVC)
            else {
                transitionContext.completeTransition(false)
                return
        }

        let frame = transitionContext.initialFrame(for: fromVC)
        var fromFrameEnd = frame
        var toFrameStart = frame
        let quarterFrame = frame.width * 0.25
        fromFrameEnd.origin.x = toIndex > fromIndex ? frame.origin.x - quarterFrame : frame.origin.x + quarterFrame
        toFrameStart.origin.x = toIndex > fromIndex ? frame.origin.x + quarterFrame : frame.origin.x - quarterFrame
        toView.frame = toFrameStart

        let toCoverView = fromView.snapshotView(afterScreenUpdates: false)
        if let toCoverView = toCoverView {
            toView.addSubview(toCoverView)
        }
        let fromCoverView = toView.snapshotView(afterScreenUpdates: false)
        if let fromCoverView = fromCoverView {
            fromView.addSubview(fromCoverView)
        }

        DispatchQueue.main.async {
            transitionContext.containerView.addSubview(toView)
            UIView.animate(withDuration: self.transitionDuration, delay: 0, usingSpringWithDamping: 0.9, initialSpringVelocity: 0.8, options: [.curveEaseOut], animations: {
                fromView.frame = fromFrameEnd
                toView.frame = frame
                toCoverView?.alpha = 0
                fromCoverView?.alpha = 1
            }) { (success) in
                fromCoverView?.removeFromSuperview()
                toCoverView?.removeFromSuperview()
                fromView.removeFromSuperview()
                transitionContext.completeTransition(success)
            }
        }
    }

    func getIndex(forViewController vc: UIViewController) -> Int? {
        guard let vcs = self.viewControllers else { return nil }
        for (index, thisVC) in vcs.enumerated() {
            if thisVC == vc { return index }
        }
        return nil
    }
}

我唯一想知道的就是如何使它像Facebook一样“可中断”。我知道有一个interruptibleAnimator函数，但是我还无法使其正常工作。

Answer 5

要在@gmogames上进行扩展，请回答：https://stackoverflow.com/a/45362914/1993937

通过调用代码来选择选项卡栏索引时，我无法对此进行动画处理，例如：

tabBarController.setSeletedIndex(0)

似乎没有经历相同的调用层次结构，并且跳过了该方法：

tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController)

完全没有动画。

在我的代码中，除了在某些情况下以代码方式手动设置选项卡栏项目外，我还希望用户点击选项卡栏项目有一个动画过渡。

这是我对上述解决方案的补充，该解决方案添加了另一种方法，该方法通过将过渡设置动画的代码来设置所选索引：

import Foundation
import UIKit

@objc class CustomTabBarController: UITabBarController {
    override func viewDidLoad() {
        super.viewDidLoad()
        delegate = self
    }

    @objc func set(selectedIndex index : Int) {
        _ = self.tabBarController(self, shouldSelect: self.viewControllers![index])
    }
}

@objc extension CustomTabBarController: UITabBarControllerDelegate  {
    @objc func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {

        guard let fromView = selectedViewController?.view, let toView = viewController.view else {
            return false // Make sure you want this as false
        }

        if fromView != toView {

            UIView.transition(from: fromView, to: toView, duration: 0.3, options: [.transitionCrossDissolve], completion: { (true) in

            })

            self.selectedViewController = viewController
        }

        return true
    }
}

现在就打电话

tabBarController.setSelectedWithIndex(1)

进行代码内动画过渡！

我仍然认为不幸的是，要完成此操作，我们必须重写不是setter的方法并在其中处理数据。如果这是我们需要重写以完成此工作的方法，那么它不会使选项卡栏控制器具有应有的扩展性。

如何使用CrossDissolve幻灯片切换为Tab栏选项卡切换设置动画？

5 个答案:

我更改了