swift - 我试图在加载 UITableView 时显示 UIActivityIndi​​catorView

Question

这个问题已经在这个网站上回答过好几次了，我都试过了，但没有任何效果。我认为不同之处在于我的 UIViewController 中有一个 UITableView。我在 viewDidLoad 中加载数据时尝试过，这里是我从显示的屏幕，直到所有完成并出现我的新 View 。我还在 viewDidAppear 中进行了尝试，这里在最终 View 出现之前显示了一个空白表格。

我已经尝试了该网站的 4 种方法，我在开始加载之前调用 pauseApp(n)，并在完成后调用 restartApp(n)

    var spinner:UIActivityIndicatorView = UIActivityIndicatorView()
    var loadingView = UIView()
    var loadingLabel = UILabel()
    var indicator = UIActivityIndicatorView()
    @IBOutlet weak var tvTable: UITableView!

    func pauseApp() {
        tvTable.activityIndicatorView.startAnimating()
        tvTable.activityIndicatorView.bringSubviewToFront(aIV)
        UIApplication.shared.beginIgnoringInteractionEvents()
    }
    func pauseApp1() {
        spinner = UIActivityIndicatorView(frame: CGRect(x: 0, y: 0, width: 20, height: 20))
        spinner.center = self.navBar.center
        spinner.hidesWhenStopped = true
        spinner.style = UIActivityIndicatorView.Style.gray
        self.navigationController?.view.addSubview(spinner)
        spinner.startAnimating()
        UIApplication.shared.beginIgnoringInteractionEvents()
    }
    func pauseApp2() {
        tvTable.activityIndicatorView.startAnimating()
        indicator.startAnimating()
        indicator.backgroundColor = UIColor.white
        UIApplication.shared.beginIgnoringInteractionEvents()
    }
    func pauseApp3() {
        setLoadingScreen()
        UIApplication.shared.beginIgnoringInteractionEvents()
    }
    func restartApp() {
    //        sleep(2)
        tvTable.activityIndicatorView.stopAnimating()
        UIApplication.shared.endIgnoringInteractionEvents()
    }
    func restartApp1() {
        spinner.stopAnimating()
        UIApplication.shared.endIgnoringInteractionEvents()
    }
    func restartApp2() {
    //        sleep(2)
        indicator.stopAnimating()
        indicator.hidesWhenStopped = true
        UIApplication.shared.endIgnoringInteractionEvents()
    }
    func restartApp3() {
    //       sleep(2)
        removeLoadingScreen()
        UIApplication.shared.endIgnoringInteractionEvents()
    }
    private func setLoadingScreen() {
        let width: CGFloat = 120
        let height: CGFloat = 30
        let x = (view.frame.width / 2) - (width / 2)
        let y = (view.frame.height / 2) - (height / 2) - 20
        loadingView.frame = CGRect(x: x, y: y, width: width, height: height)

        // Sets loading text
        loadingLabel.textColor = .gray
        loadingLabel.textAlignment = .center
        loadingLabel.text = "Loading..."
        loadingLabel.frame = CGRect(x: 0, y: 0, width: 140, height: 30)

        // Sets spinner
        spinner.style = .gray
        spinner.frame = CGRect(x: 0, y: 0, width: 30, height: 30)
        spinner.startAnimating()

        // Adds text and spinner to the view
        loadingView.addSubview(spinner)
        loadingView.addSubview(loadingLabel)

        view.addSubview(loadingView)
        view.bringSubviewToFront(loadingView)

    }
    private func removeLoadingScreen() {
        spinner.stopAnimating()
        spinner.isHidden = true
        loadingLabel.isHidden = true
    }

    func activityIndicator()  {
        indicator = UIActivityIndicatorView(frame: CGRect(x: 0, y: 0, width: 40, height: 40))
        indicator.style = UIActivityIndicatorView.Style.gray
        indicator.center = self.view.center
        self.view.addSubview(indicator)
    }
    fileprivate var ActivityIndicatorViewAssociativeKey = "ActivityIndicatorViewAssociativeKey"
    public var aIV: UIActivityIndicatorView = UIActivityIndicatorView()
    public extension UITableView {
        var activityIndicatorView: UIActivityIndicatorView {
            get {
                if let aIV = getAssociatedObject(&ActivityIndicatorViewAssociativeKey) as? UIActivityIndicatorView {
                return aIV
                } else {
                    let aIV = UIActivityIndicatorView(frame: CGRect(x: 0, y: 0, width: 40, height: 40))
                    aIV.style = .gray
                    aIV.color = .gray
                    aIV.backgroundColor = UIColor.black
                    aIV.center = center
                    aIV.hidesWhenStopped = true
                    addSubview(aIV)

                    setAssociatedObject(aIV, associativeKey: &ActivityIndicatorViewAssociativeKey, policy: .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
                   aIV.bringSubviewToFront(aIV)
                   return aIV
                }
            }

            set {
                addSubview(newValue)
                setAssociatedObject(newValue, associativeKey:&ActivityIndicatorViewAssociativeKey, policy: .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
            }
        }
    }
    public extension NSObject {
        func setAssociatedObject(_ value: AnyObject?, associativeKey: UnsafeRawPointer, policy: objc_AssociationPolicy) {
            if let valueAsAnyObject = value {
                objc_setAssociatedObject(self, associativeKey, valueAsAnyObject, policy)
            }
        }

        func getAssociatedObject(_ associativeKey: UnsafeRawPointer) -> Any? {
            guard let valueAsType = objc_getAssociatedObject(self, associativeKey) else {
                return nil
            }
            return valueAsType
        }
    }

Answer 1

验证您的 Interface Builder 文件，特别是定义组件的顺序。层次结构中较高的组件可能会被下面定义的组件隐藏。因此，您的表格 View 很可能隐藏了您的事件 View 。

您应该能够通过隐藏表格 View 和可能位于顶部的其他其他 View 来相当快地确认这一点。根据您的事件 View 设置，您可能还需要执行 tvTable.activityIndi​​catorView.isHidden = false。请注意，由于 UITableView 实现了内置 ScrollView ，因此将事件 View 作为 subview 添加到 UITableView 可能不是最好的方法。您最好将其定义为 tableView 的 super View 的 subview ；引用:

您对 pauseApp1 的尝试可以进行少量修改，但前提是您的 View Controller 托管在导航 Controller 内。您还应该始终仅在将 View 添加为 subview 之后而不是之前定义任何关系。

从头开始一个全新的项目，以下是如何通过代码显示事件指示器:

class ViewController: UIViewController {

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

        // We add some delay for fun, absolutely not required!
        DispatchQueue.main.asyncAfter(deadline: .now() + 2.0) {
            self.showSpinner()
        }
    }

    private func showSpinner() {
        let spinner = UIActivityIndicatorView.init(style: .gray)
        self.view.addSubview(spinner)
        spinner.center = self.view.center
        spinner.startAnimating()
        spinner.isHidden = false
        spinner.hidesWhenStopped = true
    }
}