Question

我有两个以模态方式打开的视图控制器。当第一个VC关闭时，应打开第二个。但是当我关闭第一个时，第二个根本不显示。有什么问题吗？

我的代码是：

self.dismiss(animated: true) {
        let flowVC = LanguageFlowViewController()
        self.present(flowVC, animated: true)
    }

Answer 1

您需要从此处提交第一个视图控制器的视图控制器参考。

例如，您的第一个视图控制器X从此处的视图控制器名称为A。因此，您需要引用X来显示B，因为A在内存中将不可用。

因此，当您尝试使用self显示第二个视图控制器时，它什么也不会做。

因此，对于解决方案，将X视图控制器的引用分配给A。在类A中，声明：

var refX: X?

从A到X时，请将self设置为refX。喜欢：

var aVC = A() // This is temp, you need to instantiate your view controller here.
aVC.refX = self
self.present(aVC, animated: true, completion: nil)

现在，在关闭时，内部视图控制器A：

var bVC = B() // This is temp, you need to instantiate your view controller here.
self.dismiss(animated: true) {
    if self.refX != nil {
        self.refX?.present(bVC, animated: true, completion: nil)
    }
}

我希望这会对您有所帮助。

Answer 2

您正在通过调用self.dismiss()来关闭当前视图控制器。因此，由于它已从视图层次结构中删除，因此无法再显示任何内容。正如其他人提到的那样，请尝试使用self.presentingViewController或self.navigationController（如果它在navigationController上）来呈现新视图。

但是，如果需要最大的灵活性，请创建一个委托协议。创建具有功能presentForChild(viewController: UIViewController)的协议。在上一个视图显示问题代码所在的视图之前，请给它提供协议的引用。

示例：

protocol ChildPresentDelegate: class {
    func presentForChild(vc: UIViewController)
}

class FirstController: UIViewController, ChildPresentDelegate {

    func presentForChild(vc: UIViewController) {
        present(vc, animated: true, completion: nil)
    }

    /**
     other code
     */

    func showControllerAsWasShownInTheQuestion() {
        let controller = SecondController()
        controller.delegate = self
        present(controller, animated: true, completion: nil)
    }
}

class SecondController: UIViewController {
    weak var delegate: ChildPresentDelegate?

    func dismissMySelf() {
        self.dismiss(animated: true) {
            delegate?.presentForChild(vc: LanguageFlowViewController())
        }
    }
}

Answer 3

If you want to open modally ThirdViewController after Dismiss SecondViewController then 
you have to create protocol for it.

Like we have three UIViewController(FirstViewController,SecondViewController and 
ThirdViewController)

Step 1: We need to create a protocol in SecondViewController as given below code.

protocol DismissedViewProtocal{
func dismissView();
}
class SecondViewController: UIViewController {
 var delegate: DismissedViewProtocal?
    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }
@IBAction func dismissSecondViewAction(_sender : AnyObject){
        dismiss(animated: true) {
            self.delegate?.dismissView();
        };

    }

Step :2 You need to add protocol in FirstViewController as given below
class FirstViewController: UIViewController,DismissedViewProtocal {
override func viewDidLoad() {
        super.viewDidLoad()
}
@IBAction func anAction(_sender : AnyObject){
        let flowVC = self.storyboard?.instantiateViewController(withIdentifier:"SecondViewController") as? SecondViewController;
        secondVC?.delegate = self;
        self.present(secondVC!, animated: true) {

        };
    }
func dismissView() {
        let thirdVC = 
self.storyboard?.instantiateViewController(withIdentifier:"ThirdViewController");
        self.present(thirdVC!, animated: true) {

        };
    }
}

在第一个模式视图控制器关闭后，显示第二个模式视图控制器

3 个答案: