对于我的标签栏 Controller ，我想要 4/5 标签的过渡。第五个选项卡我能够成功执行不同的转换，但尝试将其添加到其他 View Controller 导致崩溃。
Action Storyboard: This storyboard contains my tab bar controller, and my camera view controller. The transition for this view controller is the only one that works. When i try to transition different tabs that are not in the tab bar controllers storyboard, it crashes
这是有问题的 Storyboard
For example, I want to provide a different transition for the view controller in this storyboard. However, i get the error: Unexpectedly found nil while unwrapping an optional value
这是我的代码:
func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {
if let restoreID = viewController.restorationIdentifier {
if restoreID == "NavigationCamera" {
// This is the transition that works
if let nav = tabBarController.viewControllers![tabBarController.selectedIndex] as? UINavigationController {
print("Nav is allowed")
let newVC = tabBarController.storyboard?.instantiateViewController(withIdentifier: "CameraView")
let transition = CATransition()
transition.duration = 0.25
transition.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
transition.type = kCATransitionPush
transition.subtype = kCATransitionFromTop
nav.view.layer.add(transition, forKey: nil)
nav.pushViewController(newVC!, animated: false)
return false
}
} else {
if let otherNav = tabBarController.viewControllers![tabBarController.selectedIndex] as? UINavigationController {
print("Other nav is allowed")
let vcID = restoreID + "View"
print(vcID)
let myVC = otherNav.storyboard?.instantiateInitialViewController()
let otherTransition = CATransition()
otherTransition.duration = 0.25
otherTransition.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
otherTransition.type = kCATransitionPush
otherTransition.subtype = kCATransitionFade
otherNav.view.layer.add(otherTransition, forKey: nil)
// This is where the error occurs and crashes
otherNav.pushViewController(myVC!, animated: false)
return false
}
}
}
return true
}
我再次得到的错误是:
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
最佳答案
let storyboard = UIStoryboard(name: <other storyboard>, bundle: nil)
let myVC = storyboard.instantiateViewController(withIdentifier: <your navigation controler>)
关于ios - 实例化初始 View Controller 提供 Nil，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47588214/