效果图：

wkwebView.gif

• 目前这个版本有一个问题:发现，在加载百度的时候，如果有的网页本身带有导航栏，它的顶部的进度条就无效了，如果没有，则可以实现类似于微信一样的进度条

实现代码:

import UIKit
import WebKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.addSubview(webView)
        view.addSubview(progressView)
        view.addSubview(centerButton)
        
        webView.frame = view.bounds
        progressView.frame = CGRect(x: 0, y: 0, width: UIScreen.mainScreen().bounds.size.width, height: 2)
        centerButton.frame = CGRect(x: 0, y: 0, width: 100, height: 100)
        centerButton.center = view.center
        
        webView.addObserver(self, forKeyPath: "estimatedProgress", options: .New, context: nil)
        webView.addObserver(self, forKeyPath: "title", options: .New, context: nil)
        webView.addObserver(self, forKeyPath: "loading", options: .New, context: nil)
       
        
    }
    
    override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
        
        if keyPath == "estimatedProgress" {

            let progress = change!["new"] as! Float
            
            print(progress)
            
            if progress >= 1.0 {
                
                self.progressView.setProgress(progress, animated: true)
                
                UIView.animateWithDuration(0.3, delay: 0.3, options: .CurveEaseInOut, animations: { 
                    
                    self.progressView.alpha = 0.0
                    
                    }, completion: { (_) in
                        
                     self.progressView.setProgress(0.0, animated: false)
                })
            
            }else {
            
                self.progressView.alpha = 1.0
                self.progressView.setProgress(progress, animated: true)
            }
            
            
            
            
        }else if keyPath == "loading" {
        
        }
        else if keyPath == "title" {
        
            print(webView.title ?? "")
        }
    }
    
    @objc private func click() {
    
         webView.loadRequest(NSURLRequest(URL: NSURL(string: "https://www.baidu.com")!))
    }
    
    private lazy var webView:WKWebView = {
        
        let webView = WKWebView()
        webView.UIDelegate = self
        webView.navigationDelegate = self
        
        return webView
    }()
    
    private lazy var progressView:UIProgressView = {
        
        let progressView = UIProgressView()
        progressView.trackTintColor = UIColor.whiteColor()
        progressView.progressTintColor = UIColor.greenColor()
        
        return progressView
    }()
    
    private lazy var centerButton:UIButton = {
        
        let centerButton = UIButton()
        centerButton.backgroundColor = UIColor.orangeColor()
        centerButton.addTarget(self, action: #selector(click), forControlEvents: .TouchUpInside)
        centerButton.setTitle("点击一下", forState: .Normal)
        
        return centerButton
    }()

    deinit{
    
        removeObserver(self, forKeyPath: "estimatedProgress", context: nil)
        removeObserver(self, forKeyPath: "title", context: nil)
        removeObserver(self, forKeyPath: "loading", context: nil)
    }
}

extension ViewController : WKNavigationDelegate,WKUIDelegate {

    func webView(webView: WKWebView, decidePolicyForNavigationAction navigationAction: WKNavigationAction, decisionHandler: (WKNavigationActionPolicy) -> Void) {
    
        decisionHandler(.Allow)
    }
    
    func webView(webView: WKWebView, decidePolicyForNavigationResponse navigationResponse: WKNavigationResponse, decisionHandler: (WKNavigationResponsePolicy) -> Void) {
    
        decisionHandler(.Allow)
        
    }
    
    func webView(webView: WKWebView, didStartProvisionalNavigation navigation: WKNavigation!) {
    
    }
    
    func webView(webView: WKWebView, didReceiveServerRedirectForProvisionalNavigation navigation: WKNavigation!) {
    
    }
    
    //MARK: 加载失败
    func webView(webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation!, withError error: NSError) {
    
    }
    
    //完成加载
    func webView(webView: WKWebView, didFinishNavigation navigation: WKNavigation!) {
    
    }
}