ManualResetEvent實作執行緒的暫停與恢復-有解無憂

背景

前些天遇到一個需求，在沒有第三方原始碼的情況下，重繪一個第三方UI，并且攔截到其ajax請求的回傳結果，當結果為AVALIABLE的時候，停止重繪并語音提示，否則繼續重繪，

分析這個需求，發現需要控制一個重繪回圈的暫停與開始，因此網上搜到了通過ManualResetEvent實作執行緒的暫停與恢復，

ManualResetEvent介紹

ManualResetEvent是一個通過信號機制，實作執行緒間狀態同步的類，常用的方法有以下三個：

WaitOne：阻止當前執行緒，直到收到信號

Reset：將事件狀態設定為非終止狀態，導致執行緒阻止

Set：將事件狀態設定為終止狀態，從而允許繼續執行一個或多個等待執行緒

實作設計

1.通過CefSharp的谷歌瀏覽器插件請求第三方網站

2.具體互動邏輯如下

默認開啟一個執行緒，并通過WaitOne掛起，等待手動開始自動重繪的指令
手動通過Set方法發送開始作業信號
執行完面操作后，通過Reset將執行緒再次掛起，并等待Ajax結果，判斷Ajax結果，如果不等于AVALIABLE則再次恢復執行緒

        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";
            // 避免頁面加載不出來, 建議加上這句
            Cef.Initialize(setting);

            workerThread = new Thread(new ThreadStart(BeginListenWorkerAsync));
            workerThread.IsBackground = true;
            workerThread.Start();

            this.停止自動監聽ToolStripMenuItem.Enabled = false;
        }

        private async void BeginListenWorkerAsync()
        {
            while (true)
            {
                _eventBeginListenWorkList.WaitOne();  //1.默認掛起執行緒，等待信號
                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.頁面執行完相應操作則再次掛起執行緒，等待ajax請求結果再判斷是否恢復執行緒
            }
        }

        private void 停止自動監聽ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            this.開始自動監聽ToolStripMenuItem.Enabled = true;
            this.停止自動監聽ToolStripMenuItem.Enabled = false;
            _eventBeginListenWorkList.Reset();
            StartListen = false;
        }

        private void 開始自動監聽ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            this.開始自動監聽ToolStripMenuItem.Enabled = false;
            this.停止自動監聽ToolStripMenuItem.Enabled = true;
            _eventBeginListenWorkList.Set(); // 2.手動通過Set發送信號恢復執行緒，讓其作業
            StartListen = true;
        }

3.現在我們需要定義RequestHandler來指定ResourceHandler攔截ajax請求

        private void Form1_Load(object sender, EventArgs e)
        {
            chromiumWebBrowser1.RequestHandler = new MyRequestHandler(this);
            chromiumWebBrowser1.Load("https://www.xxxxxxxx.com/");
        }

MyRequestHandler中需要指定自定義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)
        {
            // 先呼叫基類的實作，斷點除錯
            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攔截到ajax請求之后，如果結果不是AVALIABLE則通過StartListenFunc再次恢復執行緒

    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 =https://www.cnblogs.com/chenyishi/p/ 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 = https://www.cnblogs.com/chenyishi/p/JsonConvert.DeserializeObject(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則是通過Set方法再次恢復了執行緒對ui的重復查詢

        public static void StartListenFunc()
        {
            _eventBeginListenWorkList.Set();
            StartListen = true;
        }

ManualResetEvent官方介紹如下

https://docs.microsoft.com/zh-cn/dotnet/api/system.threading.manualresetevent?view=netframework-1.1

轉載請註明出處，本文鏈接：https://www.uj5u.com/net/416145.html

標籤：ASP.NET

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