在Swift中没有发生针对UIProgressView的observeValueForKeyPath的调用

Question

With the help of this tutorial I was adding a progress bar to my view with Swift but the observer does not get any calls of itself.

//  ViewController.swift

import UIKit
import WebKit

class ViewController: UIViewController, WKNavigationDelegate {

    var webView: WKWebView?

    @IBOutlet dynamic var progressView: UIProgressView!

    override func viewDidLoad() {
        super.viewDidLoad()

        setupBrowser()

        self.addObserver(self, forKeyPath: "estimatedProgress", options: .New, context: nil)

        let website = "https://google.com"
        let site = NSURL(string: website)

        loadURLRequest(NSURLRequest(URL: site!))
    }

    func setupBrowser() {
        let wkWebView = WKWebView(frame: view.bounds)
        wkWebView.navigationDelegate = self
        webView = wkWebView

        let wkProgressView = UIProgressView(frame: view.bounds)
        progressView = wkProgressView

        self.view.insertSubview(wkWebView, belowSubview: wkProgressView)
    }

    func loadURLRequest(request: NSURLRequest) {
        webView?.loadRequest(request)
    }

    func webView(webView: WKWebView, didFinishNavigation navigation: WKNavigation!) {
        print("Finished navigating")
    }

    override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
        print(1)
        if (keyPath == "estimatedProgress") {
            // TODO
        }
    }

}

Taking a look on SWIFT - KVO in xcode 6 beta 6.. observeValueForKeyPath no longer called or observeValueForKeyPath not being called didn't help. Is UIProgressView not observable? The console shows after every page load Finished navigating but not once 1 .

Answer 1

It should be

 self.webView.addObserver(self, forKeyPath: "estimatedProgress", options: .New, context: nil)

You observe the webview estimateProgress ,get the progress,then set the progress of the progressView