ios - UIRefreshControl endRefresh 在启用大标题的情况下使用时会跳转

Question

我正在尝试使用UIRefreshControl，但是当我调用endRefreshing()时，它会跳转UINavigationBar。仅当我将 UIRefreshControl 与大标题一起使用时才会出现此问题。 看看这里报告的一些类似问题( UIRefreshControl glitching in combination with custom TableViewCell )，我尝试仅在拖动结束后刷新，但错误仍然出现。也尝试过使用

self.navigationController?.navigationBar.isTranslucent = false 和 self.extendedLayoutInincludesOpaqueBars = true

但是，在其他问题上找到的解决方案似乎都没有解决问题，仍然不顺利。

正在发生的事情的视频:

https://www.youtube.com/watch?v=2BBRnZ444bE

应用程序委托(delegate)

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?

    func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
        ) -> Bool {

        let window = UIWindow(frame: UIScreen.main.bounds)
        window.makeKeyAndVisible()
        let nav = UINavigationController()
        nav.title = "My Nav"
        nav.navigationBar.prefersLargeTitles = true
        nav.viewControllers = [ViewController()]
        window.rootViewController = nav

        self.window = window
        return true
    }

}

请注意，我使用的是大标题:

        let nav = UINavigationController()
        nav.title = "My Nav"
        nav.navigationBar.prefersLargeTitles = true

ViewController:

import UIKit
import Foundation

final class ViewController: UICollectionViewController {
    let randomHeight = Int.random(in: 100..<300)

    init() {
        let layout = UICollectionViewFlowLayout()
        layout.scrollDirection = .vertical
        layout.estimatedItemSize = CGSize(width: 20, height: 20)
        super.init(collectionViewLayout: layout)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        navigationItem.title = "Try to refresh"

        self.navigationController?.navigationBar.isTranslucent = false
        self.extendedLayoutIncludesOpaqueBars = true

        collectionView.backgroundColor = .white
        registerCells()
        setupRefreshControl()
    }

    private func registerCells() {
        self.collectionView.register(
            Cell.self,
            forCellWithReuseIdentifier: "Cell"
        )
    }

    private func setupRefreshControl() {
        let refreshControl = UIRefreshControl()
        refreshControl.addTarget(
            self,
            action: #selector(refreshControlDidFire),
            for: .valueChanged
        )
        self.collectionView.refreshControl = refreshControl
    }

    @objc private func refreshControlDidFire(_ sender: Any?) {
        if let sender = sender as? UIRefreshControl, sender.isRefreshing {
            refresh()
        }
    }

    override func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
        if collectionView.refreshControl!.isRefreshing {
            refresh()
        }
    }

    private func refresh() {
        if !collectionView.isDragging {
            collectionView.refreshControl!.endRefreshing()
            collectionView.perform(#selector(collectionView.reloadData), with: nil, afterDelay: 0.05)
        }
    }
}

extension ViewController {
    override func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }

    override func collectionView(
        _ collectionView: UICollectionView,
        numberOfItemsInSection section: Int
        ) -> Int {
        return 10
    }

    override func collectionView(_ collectionView: UICollectionView,
                                 cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        guard let cell = collectionView.dequeueReusableCell(
            withReuseIdentifier: "Cell", for: indexPath
            ) as? Cell else {
                return UICollectionViewCell()
        }

        cell.label.text = "Text number \(indexPath.row), with height \(randomHeight)"
        cell.heightAnchorConstraint.constant = CGFloat(randomHeight)
        return cell
    }
}

extension ViewController: UICollectionViewDelegateFlowLayout {

    func collectionView(_ collectionView: UICollectionView,
                        layout collectionViewLayout: UICollectionViewLayout,
                        insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: 20, left: 0, bottom: 0, right: 0)
    }
}

final class Cell: UICollectionViewCell {
    private let shadowView = UIView()
    private let containerView = UIView()
    private let content = UIView()
    let label = UILabel()
    var heightAnchorConstraint: NSLayoutConstraint!

    override init(frame: CGRect = .zero) {
        super.init(frame: frame)
        setupViews()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    private func setupViews() {
        insertSubview(shadowView, at: 0)
        addSubview(containerView)
        containerView.addSubview(label)
        containerView.addSubview(content)
        activateConstraints()
    }

    private func activateConstraints() {
        self.translatesAutoresizingMaskIntoConstraints = false
        shadowView.translatesAutoresizingMaskIntoConstraints = false
        containerView.translatesAutoresizingMaskIntoConstraints = false
        label.translatesAutoresizingMaskIntoConstraints = false
        content.translatesAutoresizingMaskIntoConstraints = false

        shadowView.topAnchor.constraint(equalTo: self.topAnchor).isActive = true
        shadowView.leadingAnchor.constraint(equalTo: self.leadingAnchor).isActive = true
        shadowView.trailingAnchor.constraint(equalTo: self.trailingAnchor).isActive = true
        shadowView.bottomAnchor
            .constraint(equalTo: self.bottomAnchor).isActive = true

        containerView.backgroundColor = .white
        containerView.layer.cornerRadius = 14

        containerView.topAnchor.constraint(equalTo: self.topAnchor).isActive = true
        containerView.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
        containerView.leadingAnchor.constraint(equalTo: self.leadingAnchor).isActive = true
        containerView.trailingAnchor.constraint(equalTo: self.trailingAnchor).isActive = true
        let widthAnchorConstraint = containerView.widthAnchor.constraint(equalToConstant: UIScreen.main.bounds.width - 20)
        widthAnchorConstraint.identifier = "Width ContainerView"
        widthAnchorConstraint.priority = .defaultHigh
        widthAnchorConstraint.isActive = true

        label.numberOfLines = 0
        label.textAlignment = .center
        label.centerXAnchor.constraint(equalTo: containerView.centerXAnchor).isActive = true
        label.centerYAnchor.constraint(equalTo: containerView.centerYAnchor).isActive = true
        label.leadingAnchor.constraint(equalTo: containerView.leadingAnchor).isActive = true
        label.trailingAnchor.constraint(equalTo: containerView.trailingAnchor).isActive = true

        content.leadingAnchor.constraint(equalTo: containerView.leadingAnchor, constant: 20).isActive = true
        content.topAnchor.constraint(equalTo: containerView.topAnchor, constant: 10).isActive = true
        content.bottomAnchor.constraint(lessThanOrEqualTo: containerView.bottomAnchor, constant: -10).isActive = true
        heightAnchorConstraint = content.heightAnchor.constraint(greaterThanOrEqualToConstant: 220)
        heightAnchorConstraint.identifier = "Height Content"
        heightAnchorConstraint.priority = .defaultHigh
        heightAnchorConstraint.isActive = true
        content.widthAnchor.constraint(equalToConstant: 40).isActive = true
        content.backgroundColor = .red

    }

    override func layoutSubviews() {
        super.layoutSubviews()
        applyShadow(width: 0.20, height: -0.064)
    }

    private func applyShadow(width: CGFloat, height: CGFloat) {
        let shadowPath = UIBezierPath(roundedRect: shadowView.bounds, cornerRadius: 14.0)
        shadowView.layer.masksToBounds = false
        shadowView.layer.shadowRadius = 8.0
        shadowView.layer.shadowColor = UIColor.black.cgColor
        shadowView.layer.shadowOffset = CGSize(width: width, height: height)
        shadowView.layer.shadowOpacity = 0.3
        shadowView.layer.shadowPath = shadowPath.cgPath
    }
}

Answer 1

该问题与layout.estimatedItemSize = CGSize(width: 20, height: 20)有关

当我们使用AutoLayout调整单元格大小时，它会产生一个UIRefreshControl和导航栏大标题的错误。因此，如果您使用的 layout.estimatedItemSize 的大小等于或大于我们的预期。所以 bug 不会发生，故障也不会发生。

基本上，问题是当我们调用 updateData 但单元格比我们预期的大时，UICollectinView 的每个单元格将调整为比 >UICollectionViewController 会出现故障。