获取UINavigationController向后滑动的进度 [英] Get progress of UINavigationController swipe back

问题描述

我有两个 viewControllers ，它们都是 UINavigationController 的一部分.在 View1 中，我可以点击 UITableViewCell 并转到 View2 ，在 View2 中，我可以滑动回View1 .

I have two viewControllers, both are part of a UINavigationController. From View1 I can tap a UITableViewCell and go to View2, from View2 I can swipe back to View1.

我想知道如何获得过渡的进展，但是我在以下方面没有成功:

I would like to know how I can get the progress of this transition, and I have been unsuccessful with the following:

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

该 going 函数在过渡期间被调用很多，但是该print语句仅打印 nil .我尝试使用其他视图控制器(View1和父级导航控制器)都无济于事.

That going function is called a lot during the transition, but that print statement just prints nil. I tried with other view controller (both View1 and the parent nav controller) to no avail.

预先感谢

推荐答案

这似乎可行:

    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)
        }

    }

放开之后，就无法获得进步.我尝试将协调器保留更长的时间，并在计时器上打印值，但我甚至崩溃了.

After you let go there is no way to get progress though. I tried preserving the coordinator for a bit longer and printing values on timer but I get a crash even.

无论如何，我认为这就是您所需要的.

Anyway, I assume this is what you need.

测试场景:

创建一个新项目，然后导航到主故事板.添加一个导航控制器，并将其根视图控制器设置为情节提要中的 ViewController (删除自动生成的根).

Create a new project and navigate to main storyboard. Add a navigation controller and set its root view controller to ViewController in storyboard (remove the autogenerated root).

然后转到ViewController.swift并使用以下代码覆盖它:

Then go to ViewController.swift and overwrite it with following:

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)
        }

    }

}

您应该能够看到在拖动手指时打印出的百分比，从而消除了当前按下的视图控制器.

You should be able to see percentage printed out as you drag your finger, dismissing currently pushed view controller.

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