無法在Swift 3中啟動活動指示器？

Question

我是IOS的新手。 我正在嘗試在加載Web視圖時實現活動指示器，但是我無法做到這一點。在調試時，我遇到了動畫師正在啟動但看不到的動畫師。 我正在使用swift3。這里的代碼如下。請讓我知道我在做什么錯。 如果有人有足夠的資源來了解活動指標，也請提及。

class ViewController: UIViewController,UIWebViewDelegate {

   var WebView: UIWebView!

    override func viewDidLoad()
    {
        super.viewDidLoad()

        WebView = UIWebView(frame: UIScreen.main.bounds)
        WebView.delegate = self
        view.addSubview(WebView)
        if let url = URL(string: "https://apple.com")
        {
            let request = URLRequest(url: url)
            WebView.loadRequest(request)
        }
        activityindicator.startAnimating()
        activityindicator.color = UIColor.black
        activityindicator.alpha = 1
        activityindicator.isHidden = false

    }

   // weak var activityindicator: UIActivityIndicatorView!
    let activityindicator = UIActivityIndicatorView()

    func webViewDidStartLoad(_ webView: UIWebView)
    {
        activityindicator.startAnimating()
        activityindicator.color = UIColor.black
        activityindicator.alpha = 1
        activityindicator.isHidden = false


        UIApplication.shared.isNetworkActivityIndicatorVisible = true
    }

    func webViewDidFinishLoad(_ webView: UIWebView)
    {
        UIApplication.shared.isNetworkActivityIndicatorVisible = false
        activityindicator.stopAnimating()
        activityindicator.alpha = 0
        activityindicator.isHidden = true
    }

    func webView(webView: UIWebView, didFailLoadWithError error: NSError)
    {
        activityindicator.isHidden = true
    }
}

Answer 1

好像沒有將活動指示器添加到視圖中。 類似於我們添加webview的方法，將指示器居中並添加到viewDidLoad中（下面的代碼）。

activityindicator.center = self.view.center view.addSubview(activityindicator)

我也建議將全球宣言移到一個地方。 即，將指示器聲明移動到let activityindicator = UIActivityIndicatorView() ，使其位於webview的頂部下方，而不是類的中間。 這有助於快速閱讀。

Answer 2

這是您的完整代碼。 現在可以了-

import UIKit

class ViewController: UIViewController,UIWebViewDelegate {

    var WebView: UIWebView!

    override func viewDidLoad()
    {
        super.viewDidLoad()

        WebView = UIWebView(frame: UIScreen.main.bounds)
        WebView.delegate = self
        view.addSubview(WebView)
        if let url = URL(string: "https://apple.com")
        {
            let request = URLRequest(url: url)
            WebView.loadRequest(request)
        }
        activityindicator.startAnimating()
        activityindicator.center = self.view.center
        view.addSubview(activityindicator)
        activityindicator.color = UIColor.black
        activityindicator.alpha = 1   
    }
    // weak var activityindicator: UIActivityIndicatorView!
    let activityindicator = UIActivityIndicatorView()

    func webViewDidStartLoad(_ webView: UIWebView)
    {
        activityindicator.startAnimating()
        activityindicator.color = UIColor.black
        activityindicator.alpha = 1
        activityindicator.isHidden = false


        UIApplication.shared.isNetworkActivityIndicatorVisible = true
    }

    func webViewDidFinishLoad(_ webView: UIWebView)
    {
        UIApplication.shared.isNetworkActivityIndicatorVisible = false
        activityindicator.stopAnimating()
        activityindicator.alpha = 0
        activityindicator.isHidden = true
    }

    func webView(webView: UIWebView, didFailLoadWithError error: NSError)
    {
        activityindicator.isHidden = true
    }
}