快速导航控制器在尝试导航到另一个视图控制器时返回 nil

Question

我们有路由器类将视图控制器导航到另一个视图控制器，它按预期工作，但是当视图控制器堆栈随机变为零并发生崩溃时。我们试图使用它"如果让"以避免崩溃，但这里的问题是当viewControllersStack为零时出现黑屏。所以我们把它恢复了。如果导航为零，您能建议为什么导航堆栈为 nil 如何处理它吗？

private func PopOrPushToViewController(_ strControllerClass: String) {
//get the list of controllers in the stack
let viewControllersStack: [UIViewController] = self.navigationController!.viewControllers as [UIViewController]
var boolDidNaviagtion = false
for viewController in viewControllersStack {
if boolDidNaviagtion {
viewController.removeFromParent()
}
if String(describing: type(of: viewController)) == strControllerClass {
boolDidNaviagtion = true
self.navigationController?.popToViewController(viewController, animated: true)
}
}
if !boolDidNaviagtion {
let viewController = NavigationController.sharedInstance.storyboardViewControllerFromString(strControllerClass)!
self.navigationController!.pushViewController(viewController, animated: true)
}
}

class AddTripViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
@IBAction func navigate(_ sender: Any) {
popOrPushToViewController( "ListViewController")
}
}

Answer 1

问题可能是您使用了：

viewController.removeFromParent()

如果pop堆栈中的 VC，则会自动删除其他 VC。

尝试将函数更改为以下内容：

private func PopOrPushToViewController(_ strControllerClass: String) {
// get the list of controllers in the stack
if let vcStack: [UIViewController] = self.navigationController?.viewControllers {
var didPop = false
for vc in vcStack {
// if we find the desired VC already in the navVC's stack of controllers,
// pop to it, set the didPop flag to true, and quit looking
if String(describing: type(of: vc)) == strControllerClass {
self.navigationController?.popToViewController(vc, animated: true)
didPop = true
break
}
}
// if we did NOT pop to the desired VC,
// instantiate it and push it onto the stack
if !didPop {
if let vc = NavigationController.sharedInstance.storyboardViewControllerFromString(strControllerClass) {
navigationController?.pushViewController(vc, animated: true)
}
}
}
}