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所属分类：.NET技术
背景
前些天遇到一个需求，在没有第三方源码的情况下，刷新一个第三方UI，并且拦截到其ajax请求的返回结果。当结果为AVALIABLE的时候，停止刷新并语音提示，否则继续刷新。
分析这个需求，发现需要控制一个刷新循环的暂停与开始，因此网上搜到了通过ManualResetEvent实现线程的暂停与恢复。
ManualResetEvent介绍
ManualResetEvent是一个通过信号机制，实现线程间状态同步的类。常用的方法有以下三个：
WaitOne：阻止当前线程，直到收到信号
Reset：将事件状态设置为非终止状态，导致线程阻止
Set：将事件状态设置为终止状态，从而允许继续执行一个或多个等待线程
实现设计
1.通过CefSharp的谷歌浏览器插件请求第三方网站
2.具体交互逻辑如下
- 默认开启一个线程，并通过WaitOne挂起，等待手动开始自动刷新的指令
- 手动通过Set方法发送开始工作信号
- 执行完面操作后，通过Reset将线程再次挂起，并等待Ajax结果，判断Ajax结果，如果不等于AVALIABLE则再次恢复线程
public Form1() { InitializeComponent(); var setting = new CefSettings(); setting.Locale = "zh-CN"; setting.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.102 Safari/537.36"; // 避免页面加载不出来, 建议加上这句 Cef.Initialize(setting); workerThread = new Thread(new ThreadStart(BeginListenWorkerAsync)); workerThread.IsBackground = true; workerThread.Start(); this.停止自动监听ToolStripMenuItem.Enabled = false; } private async void BeginListenWorkerAsync() { while (true) { _eventBeginListenWorkList.WaitOne(); //1.默认挂起线程，等待信号 chromiumWebBrowser1.GetBrowser().MainFrame.ExecuteJavaScriptAsync(@"document.evaluate(""//*[@id='root']/div[1]/div[2]/div/div[2]/div[1]/div[1]/div/div[1]/button"", document).iterateNext().click()"); Thread.Sleep(1000); chromiumWebBrowser1.GetBrowser().MainFrame.ExecuteJavaScriptAsync(@"document.evaluate(""//*[@id='root']/div[1]/div[2]/div/div[1]/div/div/div/div[2]/div[6]/div/button"", document).iterateNext().click()"); _eventBeginListenWorkList.Reset(); //3.页面执行完相应操作则再次挂起线程，等待ajax请求结果再判断是否恢复线程 } } private void 停止自动监听ToolStripMenuItem_Click(object sender, EventArgs e) { this.开始自动监听ToolStripMenuItem.Enabled = true; this.停止自动监听ToolStripMenuItem.Enabled = false; _eventBeginListenWorkList.Reset(); StartListen = false; } private void 开始自动监听ToolStripMenuItem_Click(object sender, EventArgs e) { this.开始自动监听ToolStripMenuItem.Enabled = false; this.停止自动监听ToolStripMenuItem.Enabled = true; _eventBeginListenWorkList.Set(); // 2.手动通过Set发送信号恢复线程，让其工作 StartListen = true; }
3.现在我们需要定义RequestHandler来指定ResourceHandler拦截ajax请求
private void Form1_Load(object sender, EventArgs e) { chromiumWebBrowser1.RequestHandler = new MyRequestHandler(this); chromiumWebBrowser1.Load("https://www.xxxxxxxx.com/"); }
MyRequestHandler中需要指定自定义ResourceHandler
public class MyRequestHandler : RequestHandler { Form1 _form; public MyRequestHandler(Form1 form) { _form = form; } public static string AuthorizationValue; protected override bool OnBeforeBrowse(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, IRequest request, bool userGesture, bool isRedirect) { // 先调用基类的实现，断点调试 return base.OnBeforeBrowse(chromiumWebBrowser, browser, frame, request, userGesture, isRedirect); } protected override IResourceRequestHandler GetResourceRequestHandler(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, IRequest request, bool isNavigation, bool isDownload, string requestInitiator, ref bool disableDefaultHandling) { Console.WriteLine(request.Url); if (request.Url.StartsWith("https://www.xxxxxxxxxxxxxxxx/api") && request.Headers.AllKeys.Contains("Authorization")) { AuthorizationValue = request.Headers["Authorization"]; } return new MyResourceRequestHandler(_form); } }
4.最后ResourceRequestHandler拦截到ajax请求之后，如果结果不是AVALIABLE则通过StartListenFunc再次恢复线程
public class MyResourceRequestHandler : ResourceRequestHandler { Form1 _form; public MyResourceRequestHandler(Form1 form) { _form = form; } private Dictionary<ulong, MemoryStreamResponseFilter> responseDictionary = new Dictionary<ulong, MemoryStreamResponseFilter>(); protected override IResponseFilter GetResourceResponseFilter(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IResponse response) { var dataFilter = new MemoryStreamResponseFilter(); responseDictionary.Add(request.Identifier, dataFilter); return dataFilter; } protected override void OnResourceLoadComplete(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IResponse response, UrlRequestStatus status, long receivedContentLength) { MemoryStreamResponseFilter filter; if (responseDictionary.TryGetValue(request.Identifier, out filter)) { var data = filter.Data; if (request.Url.StartsWith("https://xxxxxxxxxxxxxxxxxxxx/oneapi")) { var available = false; string s = System.Text.Encoding.UTF8.GetString(data, 0, data.Length); Console.WriteLine(s); if (!string.IsNullOrEmpty(s)) { var responseData = JsonConvert.DeserializeObject<ScheduleResponse>(s); if (responseData != null && responseData.productPreviews != null) { foreach (var item in responseData.productPreviews) { if (item.schedule != null && item.schedule.status != null && item.schedule.status.name == "AVAILABLE") { available = true; Mp3Player.Play(); Action act = delegate () { _form.StopListen(); }; _form.Invoke(act); break; } } } } if (!available && Form1.StartListen) { Form1.StartListenFunc(); } } filter.Dispose(); } } }
而StartListenFunc则是通过Set方法再次恢复了线程对ui的重复查询
public static void StartListenFunc() { _eventBeginListenWorkList.Set(); StartListen = true; }
ManualResetEvent官方介绍如下
https://docs.microsoft.com/zh-cn/dotnet/api/system.threading.manualresetevent?view=netframework-1.1
