タブ切り替え時にアニメーションを行う

UITabbarController のタブをアニメーションで切り替わるようにする。

おおまかに次の手順

1. UIViewControllerAnimatedTransitioning プロトコルに準拠したアニメーションクラスを作成する。
2. TabBarControllerDelegate のanimationControllerForTransitionFromViewController メソッド内で上記のアニメーションクラスを返してやればOK

1.animator クラスの作成

TabAnimation

class TabAnimation: NSObject,UIViewControllerAnimatedTransitioning {

    func transitionDuration(transitionContext: UIViewControllerContextTransitioning) -> NSTimeInterval {
        return 1.0
    }

    func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
        let from:UIViewController = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey)!
        let to:UIViewController = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey)!
        var container:UIView = transitionContext.containerView()
        container.insertSubview(to.view, aboveSubview: from.view)
        to.view.alpha = 0.0;

        UIView.animateWithDuration(self.transitionDuration(transitionContext),
            animations: {() -> Void in

                println("begin")
                from.view.alpha = 0.0;
                to.view.alpha = 1.0;

            },
            completion: {(value: Bool) in
                transitionContext.completeTransition(true)
        })
    }

}

1. タブコントローラの実装

TabViewController

class TabViewController: UITabBarController,UITabBarControllerDelegate {
    override func viewDidLoad() {
        super.viewDidLoad()
 self.delegate = self
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

    func tabBarController(tabBarController: UITabBarController, didSelectViewController viewController: UIViewController) {
        println(viewController)
    }

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

作ったやつのサンプルプロジェクトはこちら
https://github.com/colorbox/Example/tree/master/AnimationTab