Question

我有两个viewControllers，都是UINavigationController的一部分。从View1我可以点按UITableViewCell并转到View2，从View2我可以刷回View1。

我想知道如何才能取得这一过渡的进展，而且我未能成功完成以下任务：

override func viewDidAppear(_ animated: Bool) {
    navigationController?.interactivePopGestureRecognizer?.addTarget(self, action: #selector(going))
}
@objc func going(){
        print(self.transitionCoordinator?.percentComplete)
}

在转换期间调用了going函数，但该print语句只打印nil。我尝试使用其他视图控制器（View1和父导航控制器）无济于事。

提前致谢

Answer 1

这似乎有用：

    private var currentTransitionCoordinator: UIViewControllerTransitionCoordinator?

    @objc private func onGesture(sender: UIGestureRecognizer) {
        switch sender.state {
        case .began, .changed:
            if let ct = navigationController?.transitionCoordinator {
                currentTransitionCoordinator = ct
            }
        case .cancelled, .ended:
            currentTransitionCoordinator = nil
        case .possible, .failed:
            break
        }

        if let currentTransitionCoordinator = currentTransitionCoordinator {
            print(currentTransitionCoordinator.percentComplete)
        }

    }

放手后，无法取得进展。我尝试将协调器保留更长时间并在计时器上打印值，但我甚至崩溃了。

无论如何，我认为这就是你所需要的。

TEST SCENARIO：

创建一个新项目并导航到主故事板。添加导航控制器并将其根视图控制器设置为storyboard中的ViewController（删除自动生成的根目录）。

然后转到ViewController.swift并用以下内容覆盖它：

import UIKit

class ViewController: UIViewController {

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        if let controller = navigationController, controller.viewControllers.count <= 1 { // Present it first time only
            view.backgroundColor = UIColor.green
            let newController = ViewController()
            newController.view.backgroundColor = UIColor.red
            navigationController?.interactivePopGestureRecognizer?.addTarget(newController, action: #selector(onGesture))
            navigationController?.pushViewController(newController, animated: true)
        }
    }

    private var currentTransitionCoordinator: UIViewControllerTransitionCoordinator?

    @objc private func onGesture(sender: UIGestureRecognizer) {
        switch sender.state {
        case .began, .changed:
            if let ct = navigationController?.transitionCoordinator {
                currentTransitionCoordinator = ct
            }
        case .cancelled, .ended:
            currentTransitionCoordinator = nil
        case .possible, .failed:
            break
        }

        if let currentTransitionCoordinator = currentTransitionCoordinator {
            print(currentTransitionCoordinator.percentComplete)
        }

    }

}

当您拖动手指时，您应该可以看到打印出的百分比，从而解除当前推送的视图控制器。

获取UINavigationController的进度

1 个答案: