Swift - 使用UIWebView和UIToolbar制作一个浏览器

import UIKit

class ViewController: UIViewController, UIWebViewDelegate, UITextFieldDelegate {
    
    @IBOutlet var btngo:UIButton!
    @IBOutlet var webview:UIWebView!
    @IBOutlet var txturl:UITextField!
    var loadIndicator:UIActivityIndicatorView!
    
    //进度条计时器
    var ptimer:Timer!
    //进度条控件
    var progBar:UIProgressView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        self.webview.delegate = self
        
        let frame = CGRect(x: 100.0, y: 100.0, width: 32.0, height: 32.0)
        loadIndicator = UIActivityIndicatorView(frame: frame)
        loadIndicator.activityIndicatorViewStyle = .gray
        self.view.addSubview(loadIndicator);
        
        txturl.delegate = self
        
        //构建浏览器工具条
        setupBrowserToolbar()
        
    }
    
    func setupBrowserToolbar()
    {
        // 创建一个浏览器工具条，并设置它的大小和位置
        let browserToolbar =  UIToolbar(frame:CGRect(x: 0, y: 20, width: 320, height: 44))
        
        // 将工具条添加到当前应用的界面中
        self.view.addSubview(browserToolbar)
        
        //创建图片工具条，但是不是直接使用文件名，而是用 Data 方式初始化 UIImage
        let path = Bundle.main.path(forResource: "back", ofType:"png")
        
        let urlStr = URL(fileURLWithPath: path!);
        let data = try? Data(contentsOf: urlStr);
        let btnback =  UIBarButtonItem(image:UIImage(data: data!), style:.plain, target:self,
                                       action:#selector(ViewController.backClicked(_:)));
        //第一个分隔按钮
        let btngap1 =  UIBarButtonItem(barButtonSystemItem:.flexibleSpace,
                                       target:nil, action:nil)
        
        // 创建前进按钮 UIBarButtonItem
        let btnforward = UIBarButtonItem(image:UIImage(named:"forward.png"),
                                         style:.plain, target:self,
                                         action:#selector(ViewController.forwardClicked(_:)))
        
        // 第二个分隔按钮，创建一个可伸缩的UIBarButtonItem
        let btngap2 =  UIBarButtonItem(barButtonSystemItem:.flexibleSpace,
                                       target:nil, action:nil)
        
        // 创建重新加载按钮 UIBarButtonItem
        let btnreload = UIBarButtonItem(image:UIImage(named:"reload.png"),
                                        style:.plain, target:self,
                                        action:#selector(ViewController.reloadClicked(_:)))
        
        //第三个分隔按钮
        let btngap3 =  UIBarButtonItem(barButtonSystemItem:.flexibleSpace,
                                       target:nil, action:nil)
        
        //创建加载停止按钮
        let btnstop = UIBarButtonItem(image:UIImage(named:"stop"),
                                      style:.plain, target:self,
                                      action:#selector(ViewController.stopClicked(_:)))
        
        //第四个分隔按钮
        let btngap4 =  UIBarButtonItem(barButtonSystemItem:.flexibleSpace,
                                       target:nil, action:nil)
        
        //创建进度工具条
        progBar = UIProgressView(progressViewStyle:UIProgressViewStyle.bar)
        
        // 设置UIProgressView的大小
        progBar.frame = CGRect(x: 0 , y: 0 , width: 80, height: 20)
        
        // 设置该进度条的初始进度为0
        progBar.progress = 0
        
        // 创建使用 UIView 的自定义的 UIBarButtonItem
        let btnprog =  UIBarButtonItem(customView:progBar)
        
        // 为工具条设置工具按钮
        browserToolbar.setItems( [btnback,btngap1,btnforward,btngap2,btnreload,
                                  btngap3,btnstop,btngap4, btnprog], animated:true)
        
        //创建计时器对象
        ptimer = Timer.scheduledTimer(timeInterval: 0.2, target:self,
                                      selector: #selector(ViewController.loadProgress),
                                      userInfo:nil,repeats:true)
        ptimer.invalidate()
    }
    
    func textFieldShouldReturn(_ textField:UITextField) -> Bool
    {
        txturl.resignFirstResponder()
        print("url Changed!")
        let url = txturl.text;
        loadUrl(url!)
        return true
    }
    /*
     在 UIWebView 加载指定 URL
     */
    func loadUrl(_ url:String)
    {
        let urlobj = URL(string:url)
        let request = URLRequest(url:urlobj!)
        webview.loadRequest(request);
    }
    
    func stopClicked(_ sender:UIBarButtonItem)
    {
        webview.stopLoading()
    }
    
    func reloadClicked(_ sender:UIBarButtonItem)
    {
        webview.reload()
    }
    
    func backClicked(_ sender:UIBarButtonItem)
    {
        webview.goBack()
    }
    
    func forwardClicked(_ sender:UIBarButtonItem)
    {
        webview.goForward()
    }
    
    @IBAction func goClicked(_ sender:UIButton)
    {
        //收起输入面板
        txturl.resignFirstResponder()
        let url = txturl.text;
        loadUrl(url!)
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
    
    func webViewDidStartLoad(_ webView:UIWebView)
    {
        progBar.setProgress(0, animated:false);
        ptimer.fire();
        loadIndicator.startAnimating();
    }
    func webViewDidFinishLoad(_ webView:UIWebView)
    {
        loadIndicator.stopAnimating();
        progBar.setProgress(1, animated:true);
        ptimer.invalidate();
    }
    func loadProgress()
    {
        // 如果进度满了，停止计时器
        if(progBar.progress >= 1.0)
        {
            // 停用计时器
            ptimer.invalidate();
        }
        else
        {
            // 改变进度条的进度值
            progBar.setProgress(progBar.progress + 0.02, animated:true);
        }
    }
    
    func webView(_ webView: UIWebView, didFailLoadWithError error: Error) {
        //999错误过滤(防止页面正在加载时候，点击stop按钮，提示NSURLErrorDomain error=-999)
        if error._code == NSURLErrorCancelled {
            return
        }

        let alertController = UIAlertController(title: "出错!",
                                                message: error.localizedDescription,
                                                preferredStyle: .alert)
        let okAction = UIAlertAction(title: "确定", style: .cancel, handler: nil)
        alertController.addAction(okAction)
        self.present(alertController, animated: true, completion: nil)
    }
}