Sto cambiando scheda a livello di codice in un'applicazione basata su barra delle schede utilizzando UITabBarController.selectedIndex. Il problema che sto cercando di risolvere è come animare la transizione tra le visualizzazioni. vale a dire. dalla visualizzazione della scheda corrente alla visualizzazione della scheda selezionata.

Il primo pensiero è stato quello di utilizzare il UITabBarControllerDelegate, ma sembra che questo non venga chiamato quando si cambia scheda a livello di programmazione. Sto ora considerando UITabBarDelegate.didSelectItem: come un possibile hook per impostare un'animazione di transizione.

Qualcuno è riuscito ad animare le transizioni? Se sì, come?

Aggiornamento 04/2016 : Justed voleva aggiornare questo per dire grazie a tutti per tutti i voti. Nota anche che questo è stato scritto originariamente molto tempo fa, quando ... prima di ARC, prima dei vincoli, prima ... di molte cose! Quindi tienilo in considerazione quando decidi se utilizzare queste tecniche. Potrebbero esserci approcci più moderni. Oh, e se ne trovi uno. Aggiungi una risposta in modo che tutti possano vederla. Grazie.

Qualche tempo dopo ...

Dopo molte ricerche ho trovato due soluzioni di lavoro. Entrambi hanno funzionato e fatto l'animazione tra le schede.

Soluzione 1: transizione dalla visualizzazione (semplice)

Questo è il più semplice e utilizza un metodo di transizione UIView predefinito. Con questa soluzione non abbiamo bisogno di gestire le viste perché il metodo fa il lavoro per noi.

// Get views. controllerIndex is passed in as the controller we want to go to. 
UIView * fromView = tabBarController.selectedViewController.view;
UIView * toView = [[tabBarController.viewControllers objectAtIndex:controllerIndex] view];

// Transition using a page curl.
[UIView transitionFromView:fromView 
                    toView:toView 
                  duration:0.5 
                   options:(controllerIndex > tabBarController.selectedIndex ? UIViewAnimationOptionTransitionCurlUp : UIViewAnimationOptionTransitionCurlDown)
                completion:^(BOOL finished) {
                    if (finished) {
                        tabBarController.selectedIndex = controllerIndex;
                    }
                }];

Soluzione 2: scorrimento (più complesso)

Una soluzione più complessa, ma che offre un maggiore controllo sull'animazione. In questo esempio si ottengono le visualizzazioni da attivare e disattivare. Con questo dobbiamo gestire noi stessi le visualizzazioni.

// Get the views.
UIView * fromView = tabBarController.selectedViewController.view;
UIView * toView = [[tabBarController.viewControllers objectAtIndex:controllerIndex] view];

// Get the size of the view area.
CGRect viewSize = fromView.frame;
BOOL scrollRight = controllerIndex > tabBarController.selectedIndex;

// Add the to view to the tab bar view.
[fromView.superview addSubview:toView];

// Position it off screen.
toView.frame = CGRectMake((scrollRight ? 320 : -320), viewSize.origin.y, 320, viewSize.size.height);

[UIView animateWithDuration:0.3 
                 animations: ^{

                     // Animate the views on and off the screen. This will appear to slide.
                     fromView.frame =CGRectMake((scrollRight ? -320 : 320), viewSize.origin.y, 320, viewSize.size.height);
                     toView.frame =CGRectMake(0, viewSize.origin.y, 320, viewSize.size.height);
                 }

                 completion:^(BOOL finished) {
                     if (finished) {

                         // Remove the old view from the tabbar view.
                         [fromView removeFromSuperview];
                         tabBarController.selectedIndex = controllerIndex;                
                     }
                 }];

Questa soluzione in Swift:

extension TabViewController: UITabBarControllerDelegate {
      public func tabBarController(tabBarController: UITabBarController, shouldSelectViewController viewController: UIViewController) -> Bool {

           let fromView: UIView = tabBarController.selectedViewController!.view
           let toView  : UIView = viewController.view
           if fromView == toView {
                 return false
           }

           UIView.transitionFromView(fromView, toView: toView, duration: 0.3, options: UIViewAnimationOptions.TransitionCrossDissolve) { (finished:Bool) in

        }
        return true
   }
}

di seguito è il mio tentativo di utilizzare il modulo di codice drekka nel metodo delegato (UITabBarControllerDelegate)

- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController {

    NSArray *tabViewControllers = tabBarController.viewControllers;
    UIView * fromView = tabBarController.selectedViewController.view;
    UIView * toView = viewController.view;
    if (fromView == toView)
        return false;
    NSUInteger fromIndex = [tabViewControllers indexOfObject:tabBarController.selectedViewController];
    NSUInteger toIndex = [tabViewControllers indexOfObject:viewController];

    [UIView transitionFromView:fromView
                        toView:toView
                      duration:0.3
                       options: toIndex > fromIndex ? UIViewAnimationOptionTransitionFlipFromLeft : UIViewAnimationOptionTransitionFlipFromRight
                    completion:^(BOOL finished) {
                        if (finished) {
                            tabBarController.selectedIndex = toIndex;
                        }
                    }];
    return true;
}

La mia soluzione per iOS7.0 o superiore.

È possibile specificare un controller di animazione personalizzato nel delegato della barra delle schede.

Implementa un controller di animazione come questo:

@interface TabSwitchAnimationController : NSObject <UIViewControllerAnimatedTransitioning>

@end

@implementation TabSwitchAnimationController

- (NSTimeInterval)transitionDuration:(id <UIViewControllerContextTransitioning>)transitionContext
{
    return 0.2;
}

- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext
{
    UIViewController* fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIViewController* toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIView* toView = toVC.view;
    UIView* fromView = fromVC.view;

    UIView* containerView = [transitionContext containerView];
    [containerView addSubview:toView];
    toView.frame = [transitionContext finalFrameForViewController:toVC];

    // Animate by fading
    toView.alpha = 0.0;
    [UIView animateWithDuration:[self transitionDuration:transitionContext]
                          delay:0.0
                        options:UIViewAnimationOptionCurveEaseOut | UIViewAnimationOptionAllowUserInteraction
                     animations:^{
                         toView.alpha = 1.0;
                     }
                     completion:^(BOOL finished) {
                         toView.alpha = 1.0;
                         [fromView removeFromSuperview];
                         [transitionContext completeTransition:YES];
                     }];
}

@end

Quindi usalo nel tuo UITabBarControllerDelegate:

- (id <UIViewControllerAnimatedTransitioning>)tabBarController:(UITabBarController *)tabBarController
            animationControllerForTransitionFromViewController:(UIViewController *)fromVC
                                              toViewController:(UIViewController *)toVC
{
    return [[TabSwitchAnimationController alloc] init];
}

Invece di usare tabBarController:shouldSelectViewController:è meglio implementaretabBarController:animationControllerForTransitionFromViewController:toViewController:

TransitioningObject.swift

import UIKit

class TransitioningObject: NSObject, UIViewControllerAnimatedTransitioning {

    func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
        let fromView: UIView = transitionContext.viewForKey(UITransitionContextFromViewKey)!
        let toView: UIView = transitionContext.viewForKey(UITransitionContextToViewKey)!

        transitionContext.containerView().addSubview(fromView)
        transitionContext.containerView().addSubview(toView)

        UIView.transitionFromView(fromView, toView: toView, duration: transitionDuration(transitionContext), options: UIViewAnimationOptions.TransitionCrossDissolve) { finished in
            transitionContext.completeTransition(true)
        }
    }

    func transitionDuration(transitionContext: UIViewControllerContextTransitioning) -> NSTimeInterval {
        return 0.25
    }
}

TabBarViewController.swift

import UIKit

    class TabBarViewController: UITabBarController, UITabBarControllerDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        self.delegate = self
    }

    // MARK: - Tabbar delegate

    func tabBarController(tabBarController: UITabBarController, animationControllerForTransitionFromViewController fromVC: UIViewController, toViewController toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return TransitioningObject()
    }
}

Penso che tu possa facilmente ottenere transizioni per UITabBarControlelr usando CATransition; Questo risolverà anche eventuali effetti collaterali dell'utilizzo di transizioneFromView: toView:

Usalo all'interno della tua classe TabBarController personalizzata estesa da UITabBarController.

- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController (UIViewController*)viewController {

    CATransition *animation = [CATransition animation];
    [animation setType:kCATransitionFade];
    [animation setDuration:0.25];
    [animation setTimingFunction:[CAMediaTimingFunction functionWithName:
                              kCAMediaTimingFunctionEaseIn]];
    [self.view.window.layer addAnimation:animation forKey:@"fadeTransition"];
}

Spero che questo ti aiuti :)

Ho scritto un post dopo aver provato le varie risposte qui.

Il codice è in Swift e puoi modificare programmaticamente la scheda con l'animazione chiamando animateToTab.

func animateToTab(toIndex: Int) {
    let tabViewControllers = viewControllers!
    let fromView = selectedViewController!.view
    let toView = tabViewControllers[toIndex].view    
    let fromIndex = tabViewControllers.indexOf(selectedViewController!)

    guard 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.mainScreen().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.userInteractionEnabled = false

    UIView.animateWithDuration(0.5, delay: 0.0, usingSpringWithDamping: 1, initialSpringVelocity: 0, options: UIViewAnimationOptions.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.userInteractionEnabled = true
        })
}

Se desideri che tutte le modifiche alle schede abbiano l'animazione, agganciala in modo UITabBarControllerDelegateche sia simile:

func tabBarController(tabBarController: UITabBarController, shouldSelectViewController viewController: UIViewController) -> Bool {
    let tabViewControllers = tabBarController.viewControllers!
    guard let toIndex = tabViewControllers.indexOf(viewController) else {
        return false
    }

    // Our method
    animateToTab(toIndex)

    return true
}

La mia soluzione in Swift:

Crea una classe TabBar personalizzata e impostala nella TabBar dello storyboard

class MainTabBarController: UITabBarController, UITabBarControllerDelegate {

override func viewDidLoad() {
    super.viewDidLoad()
    self.delegate = self
    // Do any additional setup after loading the view.
}

func tabBarController(tabBarController: UITabBarController, shouldSelectViewController viewController: UIViewController) -> Bool {


    let tabViewControllers = tabBarController.viewControllers!
    let fromView = tabBarController.selectedViewController!.view
    let toView = viewController.view

    if (fromView == toView) {
        return false
    }

    let fromIndex = tabViewControllers.indexOf(tabBarController.selectedViewController!)
    let toIndex = tabViewControllers.indexOf(viewController)

    let offScreenRight = CGAffineTransformMakeTranslation(toView.frame.width, 0)
    let offScreenLeft = CGAffineTransformMakeTranslation(-toView.frame.width, 0)

    // start the toView to the right of the screen


    if (toIndex < fromIndex) {
        toView.transform = offScreenLeft
        fromView.transform = offScreenRight
    } else {
        toView.transform = offScreenRight
        fromView.transform = offScreenLeft
    }

    fromView.tag = 124
    toView.addSubview(fromView)

    self.view.userInteractionEnabled = false
    UIView.animateWithDuration(0.5, delay: 0.0, usingSpringWithDamping: 1, initialSpringVelocity: 0, options: UIViewAnimationOptions.CurveEaseOut, animations: {

        toView.transform = CGAffineTransformIdentity

        }, completion: { finished in

            let subViews = toView.subviews
            for subview in subViews{
                if (subview.tag == 124) {
                    subview.removeFromSuperview()
                }
            }
            tabBarController.selectedIndex = toIndex!
            self.view.userInteractionEnabled = true

    })

    return true
 }

}

Ho usato la soluzione di @ Mofumofu e l'ho aggiornata a Swift 1.2 e ho anche implementato un'animazione su / giù. Significa che il nuovo ViewController viene visualizzato e spinge quello vecchio se l'indice del nuovo viewcontroller è maggiore di quello vecchio. Altrimenti la direzione è verso il basso.

class TabScrollPageAnimationController: NSObject, UIViewControllerAnimatedTransitioning {

    let tabBarController: UITabBarController

    init(tabBarController: UITabBarController) {
        self.tabBarController = tabBarController
    }

    func transitionDuration(transitionContext: UIViewControllerContextTransitioning) -> NSTimeInterval {
        return 0.5
    }

    func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
        if let fromVC = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey),
            let toVC = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey) {
                let fromView = fromVC.view
                let toView = toVC.view

                let containerView = transitionContext.containerView()

                var directionUpwardMultiplier: CGFloat = 1.0
                if let vcs = tabBarController.viewControllers as? [UIViewController],
                    let fIndex = find(vcs, fromVC),
                    let tIndex = find(vcs, toVC) {
                        directionUpwardMultiplier = (fIndex < tIndex) ? +1.0 : -1.0
                }

                containerView.clipsToBounds = false
                containerView.addSubview(toView)

                var fromViewEndFrame = fromView.frame
                fromViewEndFrame.origin.y -= (containerView.frame.height * directionUpwardMultiplier)

                let toViewEndFrame = transitionContext.finalFrameForViewController(toVC)
                var toViewStartFrame = toViewEndFrame
                toViewStartFrame.origin.y += (containerView.frame.height * directionUpwardMultiplier)
                toView.frame = toViewStartFrame

                toView.alpha = 0.0
                UIView.animateWithDuration(transitionDuration(transitionContext), delay: 0.0, usingSpringWithDamping: 1.0, initialSpringVelocity: 0.0, options: UIViewAnimationOptions.CurveEaseInOut, animations: { () -> Void in
                    toView.alpha = 1.0
                    toView.frame = toViewEndFrame
                    fromView.alpha = 0.0
                    fromView.frame = fromViewEndFrame
                }, completion: { (completed) -> Void in
                    toView.alpha = 1.0
                    fromView.removeFromSuperview()
                    transitionContext.completeTransition(completed)
                    containerView.clipsToBounds = true
                })

        }
    }

}

In Container ViewController:

extension XYViewController: UITabBarControllerDelegate {

    func tabBarController(tabBarController: UITabBarController, animationControllerForTransitionFromViewController fromVC: UIViewController, toViewController toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return TabScrollPageAnimationController(tabBarController: tabBarController)
    }

}

Ecco la mia soluzione Swift 3:

Eseguo l'override di selectedIndex del mio UITabBarViewController in questo modo:

override var selectedIndex: Int{
    get{
        return super.selectedIndex
    }
    set{
        animateToTab(toIndex: newValue)
        super.selectedIndex = newValue
    }
}

Quindi utilizzo questa funzione che imita l'animazione push / pop nativa:

func animateToTab(toIndex: Int) {
    guard let tabViewControllers = viewControllers, tabViewControllers.count > toIndex, let fromViewController = selectedViewController, let fromIndex = tabViewControllers.index(of: fromViewController), fromIndex != toIndex else {return}

    view.isUserInteractionEnabled = false

    let toViewController = tabViewControllers[toIndex]
    let push = toIndex > fromIndex
    let bounds = UIScreen.main.bounds

    let offScreenCenter = CGPoint(x: fromViewController.view.center.x + bounds.width, y: toViewController.view.center.y)
    let partiallyOffCenter = CGPoint(x: fromViewController.view.center.x - bounds.width*0.25, y: fromViewController.view.center.y)

    if push{
        fromViewController.view.superview?.addSubview(toViewController.view)
        toViewController.view.center = offScreenCenter
    }else{
        fromViewController.view.superview?.insertSubview(toViewController.view, belowSubview: fromViewController.view)
        toViewController.view.center = partiallyOffCenter
    }

    UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 0, options: .curveEaseIn, animations: {
        toViewController.view.center   = fromViewController.view.center
        fromViewController.view.center = push ? partiallyOffCenter : offScreenCenter
    }, completion: { finished in
        fromViewController.view.removeFromSuperview()
        self.view.isUserInteractionEnabled = true
    })
}

Spero possa essere d'aiuto :)

una correzione per l'animazione nervosa ...

UIView * fromView = self.view.superview;

questo può essere risolto in due modi

1 - Scrivilo una volta nel tuo file AppDelegate.m. Ricorda di includere UITabBarControllerDelegate usando <> dopo i due punti (:) nel tuo AppDelegate.h

-(void)tabBarController:(UITabBarController *)tabBarControllerThis didSelectViewController:(UIViewController *)viewController
{
    [UIView transitionWithView:viewController.view
                      duration:0.1
                       options:UIViewAnimationOptionAllowUserInteraction | UIViewAnimationOptionTransitionCrossDissolve
                    animations:^(void){
                    } completion:^(BOOL finished){
                        [UIView beginAnimations:@"animation" context:nil];
                        [UIView setAnimationDuration:0.7];
                        [UIView setAnimationBeginsFromCurrentState:YES];
                        [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft
                                               forView:viewController.view
                                                 cache:NO];
                        [UIView commitAnimations];
                    }];
}

2 - Scrivilo in ogni tuo file ViewController.m

-(void)viewWillAppear:(BOOL)animated
{
    [UIView transitionWithView:self.view
                      duration:1.0
                       options:UIViewAnimationOptionAllowUserInteraction | UIViewAnimationOptionTransitionCrossDissolve
                    animations:^(void){
                        [super viewWillAppear:YES];
                    } completion:^(BOOL finished){
                    }];
}

spero che questo aiuto ...!

È possibile animare in base all'elemento toccato: in questo esempio, flipFromLeft se l'indice toccato è> dell'indice selezionato in precedenza e flipFromRight se l'indice toccato è <dell'indice selezionato in precedenza. Questo è Swift 4: implementa il metodo UITabBarControllerDelegate

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

    let fromView: UIView = tabBarController.selectedViewController!.view
    let toView: UIView = viewController.view

    if fromView == toView {
        return false
    }

    if let tappedIndex = tabBarController.viewControllers?.index(of: viewController) {
        if tappedIndex > tabBarController.selectedIndex {
            UIView.transition(from: fromView, to: toView, duration: 0.5, options: UIViewAnimationOptions.transitionFlipFromLeft, completion: nil)
        } else {
            UIView.transition(from: fromView, to: toView, duration: 0.5, options: UIViewAnimationOptions.transitionFlipFromRight, completion: nil)
        }
    }
    return true
}

La risposta di drekka è davvero fantastica. Ho ottimizzato leggermente la transizione di scorrimento in modo che l'animazione assomigliasse più all'animazione push di Apple. Ho aggiunto un'animazione aggiuntiva al completamento della prima animazione per ottenere l'effetto di scorrimento corretto.

// Disable interaction during animation to avoids bugs.
self.tabBarController.view.userInteractionEnabled = NO;

// Get the views.
UIView * fromView = tabBarController.selectedViewController.view;
UIView * toView = [[tabBarController.viewControllers objectAtIndex:controllerIndex] view];

// Get the size of the view area.
CGRect viewSize = fromView.frame;
BOOL scrollRight = controllerIndex > tabBarController.selectedIndex;

// Add the to view to the tab bar view.
[fromView.superview addSubview:toView];
[fromView.superview addSubview:fromView];

self.tabBarController.selectedIndex = 0;

// Position it off screen.
toView.frame = CGRectMake((scrollRight ? (viewSize.size.width *.25) : -(viewSize.size.width * .25 )), viewSize.origin.y, viewSize.size.width, viewSize.size.height);

[UIView animateWithDuration:0.25 
             animations: ^{
                 // Animate the views on and off the screen.
                 [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
                 fromView.frame = CGRectMake(viewSize.size.width * .95, viewSize.origin.y, viewSize.size.width, viewSize.size.height);
                 toView.frame = CGRectMake((viewSize.origin.x * .90), viewSize.origin.y, viewSize.size.width, viewSize.size.height);
             }

             completion:^(BOOL finished) {
                 if (finished) {
                     // Being new animation.
                     [UIView animateWithDuration:0.2
                                          animations: ^{
                                              [UIView setAnimationCurve:UIViewAnimationCurveLinear];
                                              fromView.frame = CGRectMake(viewSize.size.width, viewSize.origin.y, viewSize.size.width, viewSize.size.height);
                                              toView.frame = CGRectMake((viewSize.origin.x), viewSize.origin.y, viewSize.size.width, viewSize.size.height);
                                          }
                                          completion:^(BOOL finished) {
                                              if (finished) {
                                                  // Remove the old view from the tabbar view.
                                                  [fromView removeFromSuperview];
                                                  // Restore interaction.
                                                  self.tabBarController.view.userInteractionEnabled = YES;
                                              }
                                          }];
                 }
             }];

Volevo usare una transizione di inversione tra due controller di visualizzazione figlio premendo un pulsante e l'ho ottenuta come segue:

-(IBAction)flipViewControllers:(id)sender{
    NSUInteger index = self.selectedIndex;
    index++;
    if(index >= self.childViewControllers.count){
        index = 0;
    }

    self.selectedIndex = index;

    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:0.75];
    [UIView setAnimationTransition:index % 2 ? UIViewAnimationTransitionFlipFromLeft : UIViewAnimationTransitionFlipFromRight
                           forView:self.view
                             cache:YES];
    [UIView commitAnimations];
}

Ho anche impostato il colore di sfondo sul nero, nel mio caso l'ho fatto impostando il navigationController.view.backgroundColor ma nel tuo caso potrebbe essere il window.backgroundColor che può essere facilmente impostato nel delegato dell'app.

Ecco il mio codice funzionante ( per 3 schede , non l'ho provato su più !!) per animare le transizioni tra le schede. Si basa principalmente sulla soluzione di drekka, ma è già implementato nel metodo delegato della barra delle schede, quindi dovrebbe funzionare se lo si copia / incolla .. (non si sa mai!)

-(BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController {

// Important! We validate that the selected tab is not the current tab, to avoid misplacing views
if (tabBarController.selectedViewController == viewController) {
    return NO;
}

// Find the selected view's index
NSUInteger controllerIndex = 0;
for (UIViewController *vc in tabBarController.viewControllers) {
    if (vc == viewController) {
        controllerIndex = [tabBarController.viewControllers indexOfObject:vc];
    }
}

CGFloat screenWidth = SCREEN_SIZE.width;

// Note: We must invert the views according to the direction of the scrolling ( FROM Left TO right or FROM right TO left )
UIView * fromView = tabBarController.selectedViewController.view;
UIView * toView = viewController.view;

[fromView.superview addSubview:toView];
CGRect fromViewInitialFrame = fromView.frame;
CGRect fromViewNewframe = fromView.frame;

CGRect toViewInitialFrame = toView.frame;

if ( controllerIndex > tabBarController.selectedIndex ) {
// FROM left TO right ( tab0 to tab1 or tab2 )

    // The final frame for the current view. It will be displaced to the left
    fromViewNewframe.origin.x = -screenWidth;
    // The initial frame for the new view. It will be displaced to the left
    toViewInitialFrame.origin.x = screenWidth;
    toView.frame = toViewInitialFrame;

} else {
// FROM right TO left ( tab2 to tab1 or tab0 )

    // The final frame for the current view. It will be displaced to the right
    fromViewNewframe.origin.x = screenWidth;
    // The initial frame for the new view. It will be displaced to the right
    toViewInitialFrame.origin.x = -screenWidth;
    toView.frame = toViewInitialFrame;
}

[UIView animateWithDuration:0.2 animations:^{
    // The new view will be placed where the initial view was placed
    toView.frame = fromViewInitialFrame;
    // The initial view will be place outside the screen bounds
    fromView.frame = fromViewNewframe;

    tabBarController.selectedIndex = controllerIndex;

    // To prevent user interaction during the animation
    [[UIApplication sharedApplication] beginIgnoringInteractionEvents];

} completion:^(BOOL finished) {

    // Before removing the initial view, we adjust its frame to avoid visual lags
    fromView.frame = CGRectMake(0, 0, fromView.frame.size.width, fromView.frame.size.height);
    [fromView removeFromSuperview];

    [[UIApplication sharedApplication] endIgnoringInteractionEvents];
}];

return NO;

}

Questo funziona per me in Swift 3:

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

    if let fromView = tabBarController.selectedViewController?.view, let toView = viewController.view {

        if fromView == toView {
            return false
        }

        UIView.transition(from: fromView, to: toView, duration: 0.2, options: .transitionCrossDissolve) { (finished) in
        }
    }

    return true
}

@samwize risposta tradotta in Swift 3 - 2 pollici in su su questo, crea un effetto pagina da sinistra a destra:

func animateToTab(toIndex: Int) {
        let tabViewControllers = viewControllers!
        let fromView = selectedViewController!.view
        let toView = tabViewControllers[toIndex].view
        let fromIndex = tabViewControllers.index(of: selectedViewController!)

        guard 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 = screenSize.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: 0.5, delay: 0.0, usingSpringWithDamping: 1, initialSpringVelocity: 0, options: UIViewAnimationOptions.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
        })
    }

Risposta di @ samwize aggiornata per Swift 5:

Se desideri che tutte le modifiche alle schede abbiano l'animazione, utilizza un UITabBarControllerDelegate e implementa questo metodo:

func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {
  let tabViewControllers = tabBarController.viewControllers!
  guard let toIndex = tabViewControllers.indexOf(value:viewController) else {
    return false
  }
  animateToTab(toIndex: toIndex, fadeOutFromView: false, fadeInToView: false)
  return true
}

Modificare la scheda con l'animazione a livello di codice chiamando animateToTab:

func animateToTab(toIndex: Int, fadeOutFromView: Bool, fadeInToView: Bool) {
  let tabViewControllers = viewControllers!
  let fromView = selectedViewController!.view
  let toView = tabViewControllers[toIndex].view
  let fromIndex = tabViewControllers.indexOf(value:selectedViewController!)
  guard 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.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
  if fadeInToView {
    toView!.alpha = 0.1
  }

  UIView.animate(withDuration: 0.5, delay: 0.0, usingSpringWithDamping: 1, initialSpringVelocity: 0, options: [.curveEaseOut], animations: {

    if fadeOutFromView {
      fromView!.alpha = 0.0
    }

    if fadeInToView {
      toView!.alpha = 1.0
    }

    // 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
  })
}

Swift 4+

Il tuo UITabBarControllerDelegatemetodo dovrebbe essere così

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

    animateToTab(toIndex: (tabBarController.viewControllers?.index(of: viewController))!)
    return true
}

E il metodo è,

func animateToTab(toIndex: Int) {
    let tabViewControllers = viewControllers!
    let fromView = selectedViewController!.view
    let toView = tabViewControllers[toIndex].view
    let fromIndex = tabViewControllers.index(of: selectedViewController!)

    guard 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: 0.5, delay: 0.0, usingSpringWithDamping: 1, initialSpringVelocity: 0, options: UIViewAnimationOptions.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
    });

}