C# 线程无法开启窗口的原因

类别:.NET开发 点击:0 评论:0 推荐:
時間: 2004/4/14
作者: Robert
參考: MSDN
電郵: [email protected]
關鍵字: 线程 Form 开启 窗口 Show Thread Invoke
目的: 幫助受 線程開啟窗口 出錯困擾的人
 
在 C# 里面, 主窗口拥有主线程, 主线程产生子线程监控 Socket 埠, 子线程一收到数据流就会给主线程发送一个事件, 创建一个窗口. 现在的情况是子线程能够收到数据流, 主窗口能够收到子线程发送过来的事件, 能够创建一个窗口. 这个窗口有问题: 窗口状态像死掉程序的窗口一样, 反白的.
开发碰到很棘手的问题, 寻找解决方法. 品味程序出错过程, 逐步跟踪程序执行过程, 每一行代码每一条语句全部执行, 怪了, 大白天碰到鬼了. 主窗口加入一个按钮, 按钮的作用就是执行主窗口的事件, 启动程序, 点击按钮, 程序正确创建一个窗口, 按照这个测试结果来看, 事件处理中的代码没有任何问题. 在执行程序, 跟踪, 寻找出错的过程. 我觉得程序没有问题, 不应该出现错误; 但是真的出错了, 说明程序一定有问题, 问题是什么呢, 没有答案; 想起以前高人语录: 计算器程序设计就是这么简单, 别管教授专家高手, 写程序出来到计算器上面一跑就知道谁的程序正确, 是骡子是马需要牵出来溜溜. 呀, 找不到答案, 转而上网, 到论坛尽量寻找这种错误相关信息, 时间浪费很多, 结果不是很好, 没有找到答案. 之后和 faust 聊天, 询问这种问题, 他指出一定是讯息回圈和线程之间交互这两个问题中的一个. 顺着 faust 的思路到论坛寻找答案, 很快找到相关讯息.
揭晓最终解决答案, 事件是一个同步处理过程, 就是说虽然子线程触发主窗口事件, 可是执行的线程仍然是子线程, 创建一个窗口 From frm1 = new Form(); Form.Show(); 能够执行, 可是无法收到 Windows Print() 事件, 所以窗口创建没有问题, 就是没有画出窗口上面的东东, 所以窗口像死掉的窗口一样, 反白的. 找到原因怎么处理问题呢? 在线程里面使用 delegateDefine delegateTest = new delegateDefine(this.m_from.eventFunction); this.m_from.Invoke(delegateTest); 就能正常执行程序了. 解决里面最重要的是 Invoke, 如果有兴趣可以看看 Invoke 的介绍.
从问题出现到问题搞定, 花费十个小时, 太辛苦了.
 
 
附: 异步委派程序设计范例
下列程序代码示范 .NET 异步程序设计的用法,使用简单类别将一些数字因子分解。
[C#]
using System;
using System.Threading;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Messaging;
 
// Create an asynchronous delegate.
public delegate bool FactorizingAsyncDelegate (
         int factorizableNum,
         ref int primefactor1,
         ref int primefactor2);
 
// Create a class that factorizers the number.
public class PrimeFactorizer
{
   public bool Factorize(
                int factorizableNum, 
                ref int primefactor1,
                ref int primefactor2)
   {
      primefactor1 = 1;
      primefactor2 = factorizableNum;
 
      // Factorize using a low-tech approach.
      for (int i=2;i<factorizableNum;i++)
      {
         if (0 == (factorizableNum % i))
         {
            primefactor1 = i;
            primefactor2 = factorizableNum / i;
            break;
         }
      }
 
      if (1 == primefactor1 )
         return false;
      else
         return true   ;
   }
}
 
// Class that receives a callback when the results are available.
public class ProcessFactorizedNumber
{
   private int _ulNumber;
 
   public ProcessFactorizedNumber(int number)
   {
      _ulNumber = number;
   }
 
   // Note that the qualifier is one-way.
   [OneWayAttribute()]
   public void FactorizedResults(IAsyncResult ar)
   {
      int factor1=0, factor2=0;
 
      // Extract the delegate from the AsyncResult. 
      FactorizingAsyncDelegate fd = (FactorizingAsyncDelegate)((AsyncResult)ar).AsyncDelegate;
 
      // Obtain the result.
      fd.EndInvoke(ref factor1, ref factor2, ar);
 
      // Output the results.
      Console.WriteLine("On CallBack: Factors of {0} : {1} {2}",
                    _ulNumber, factor1, factor2);
   }
}
 
// Class that shows variations of using Asynchronous
public class Simple
{
   // The following demonstrates the Asynchronous Pattern using a callback.
   public void FactorizeNumber1()
   {
      // The following is the client code.
      PrimeFactorizer pf = new PrimeFactorizer();
      FactorizingAsyncDelegate fd = new FactorizingAsyncDelegate (pf.Factorize);
 
      int factorizableNum = 1000589023, temp=0;
 
      // Create an instance of the class that is going
      // to be called when the call completes.
      ProcessFactorizedNumber fc = new ProcessFactorizedNumber(factorizableNum);
 
      // Define the AsyncCallback delegate.
      AsyncCallback cb = new AsyncCallback(fc.FactorizedResults);
 
      // You can use any object as the state object.
      Object state = new Object();
 
      // Asynchronously invoke the Factorize method on pf.
      IAsyncResult ar = fd.BeginInvoke(
                           factorizableNum,
                           ref temp,
                           ref temp,
                           cb,
                           state);
 
      //
      // Do some other useful work.
      //. . .
   }
 
   // The following demonstrates the Asynchronous Pattern using a BeginInvoke, followed by waiting with a time-out.
   public void FactorizeNumber2()
   {
      // The following is the client code.
      PrimeFactorizer pf = new PrimeFactorizer();
      FactorizingAsyncDelegate fd = new FactorizingAsyncDelegate (pf.Factorize);
 
      int factorizableNum = 1000589023, temp=0;
 
      // Create an instance of the class that is going
      // to be called when the call completes.
      ProcessFactorizedNumber fc = new ProcessFactorizedNumber(factorizableNum);
 
      // Define the AsyncCallback delegate.
      AsyncCallback cb =
      new AsyncCallback(fc.FactorizedResults);
 
      // You can use any object as the state object.
      Object state = new Object();
 
      // Asynchronously invoke the Factorize method on pf.
      IAsyncResult ar = fd.BeginInvoke(
                        factorizableNum,
                        ref temp,
                        ref temp,
                        null,
                        null);
 
      ar.AsyncWaitHandle.WaitOne(10000, false);
 
      if (ar.IsCompleted)
      {
         int factor1=0, factor2=0;
 
         // Obtain the result.
         fd.EndInvoke(ref factor1, ref factor2, ar);
 
         // Output the results.
 
         Console.WriteLine("Sequential : Factors of {0} : {1} {2}",
                       factorizableNum, factor1, factor2);
 
      }
   }
 
 
   public static void Main(String[] args)
   {
      Simple simple = new Simple();
      simple.FactorizeNumber1();
      simple.FactorizeNumber2();
   }
}

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