C#后台线程和UI的交互 (转)

在C#中，从Main()方法开始一个默认的线程，一般称之为主线程，如果在这个进行一些非常耗CPU的计算，那么UI界面就会被挂起而处于假死状态，也就是说无法和用户进行交互了，特别是要用类似进度条来实时显示一些提示信息的时候，这种情况就显得很糟糕。如果多开一些线程来完成一些耗时的计算，那么工作线程也是无法如此更新UI界面中的元素的，比如直接显示一个提示信息：label1.Text=outstring，原因很简单UI属于默认的主线程，而线程间是不能这样直接访问彼此的成员的。
  如果要解决以上的两个问题，那么可以借助C#中的Delegate和控件类中的Invoke()方法来搞定。
  这里给出的例子比较简单，主要思路是：在Main()中启动其它的线程作为后台进程，其中一个线程是实时显示当前的时间，一个线程是显示一些随机数，这样一来三个线程同时运行，彼此通过代理来联系。

Code

using System;

using System.Drawing;

using System.Collections;

using System.ComponentModel;

using System.Windows.Forms;

using System.Data;

using System.Threading;

namespace MutliThreadedWinFormsApp

{

public class Form1 : System.Windows.Forms.Form

{

private Thread currentTimeThread = null;

private Thread randomNumbersThread = null;

private System.Windows.Forms.Label label1;

private System.Windows.Forms.TextBox currentTime;

private System.Windows.Forms.Label label2;

private System.Windows.Forms.TextBox randomNumbers;

private System.Windows.Forms.GroupBox threadManager;

private System.Windows.Forms.Button pause;

private System.Windows.Forms.Button stop;

private System.Windows.Forms.Button start;

private System.Windows.Forms.RadioButton manageTime;

private System.Windows.Forms.RadioButton manageNumbers;

private System.Windows.Forms.RadioButton manageBoth;

private System.ComponentModel.Container components = null;

public Form1()

{

InitializeComponent();

//创建新的工作线程

currentTimeThread = new Thread(new ThreadStart(CountTime));

currentTimeThread.IsBackground = true;

randomNumbersThread = new Thread(new ThreadStart(GenerateRandomNumbers));

randomNumbersThread.IsBackground = true;

}

protected override void Dispose( bool disposing )

{

if( disposing )

{

if (components != null)

{

components.Dispose();

}

base.Dispose( disposing );

}

UI设计

[STAThread]

static void Main()

{

Application.Run(new Form1());

}

private void start_Click(object sender, System.EventArgs e)

{

bool bTime = false, bRandomNumbers = false;

if( manageTime.Checked || manageBoth.Checked )

bTime = true;

if( manageNumbers.Checked || manageBoth.Checked )

bRandomNumbers = true;

if( bTime )

currentTimeThread.Start();

if( bRandomNumbers )

randomNumbersThread.Start();

start.Enabled = false;

stop.Enabled = true;

pause.Enabled = true;

}

private void stop_Click(object sender, System.EventArgs e)

{

bool bTime = false, bRandomNumbers = false;

if( manageTime.Checked == true || manageBoth.Checked == true )

bTime = true;

if( manageNumbers.Checked == true || manageBoth.Checked == true )

bRandomNumbers = true;

if( bTime )

{

currentTimeThread.Abort();

currentTimeThread.Join();

currentTimeThread = new Thread(new ThreadStart(CountTime));

currentTimeThread.IsBackground = true;

}

if( bRandomNumbers )

{

randomNumbersThread.Abort();

randomNumbersThread.Join();

randomNumbersThread = new Thread(new ThreadStart(GenerateRandomNumbers));

randomNumbersThread.IsBackground = true;

}

start.Enabled = true;

stop.Enabled = false;

pause.Enabled = false;

}

private void pause_Click(object sender, System.EventArgs e)

{

bool bTime = false, bRandomNumbers = false;

if( manageTime.Checked == true || manageBoth.Checked == true )

bTime = true;

if( manageNumbers.Checked == true || manageBoth.Checked == true )

bRandomNumbers = true;

if( bTime )

{

if( 0 != (currentTimeThread.ThreadState & ( ThreadState.Suspended | ThreadState.SuspendRequested ) ) )

currentTimeThread.Resume();

else

currentTimeThread.Suspend();

}

if( bRandomNumbers )

{

if( 0 != (randomNumbersThread.ThreadState & ( ThreadState.Suspended | ThreadState.SuspendRequested ) ) )

randomNumbersThread.Resume();

else

randomNumbersThread.Suspend();

}

private void manageTime_CheckedChanged(object sender, System.EventArgs e)

{

}

private void manageNumbers_CheckedChanged(object sender, System.EventArgs e)

{

}

private void manageBoth_CheckedChanged(object sender, System.EventArgs e)

{

}

/// <summary>

/// 注意其Invoke的使用,其有两种使用形式

/// public void Invoke(System.Delegate delegate);

/// public void Invoke(System.Delegate delegate, object [] args);

/// </summary>

public void CountTime()

{

while(true)

{

Invoke(new UpdateTimeDelegate(updateCurrentTime));

Thread.Sleep(1000);

}

public void GenerateRandomNumbers()

{

int [] randomNumbers = new int[10];

Random r = new Random();

while(true)

{

for(int i = 0; i < randomNumbers.Length; i++)

randomNumbers[i] = r.Next(1, 100);

Invoke(new UpdateRandomNumbers(updateRandomNumbers), new object[] { randomNumbers });

Thread.Sleep(500);

}

/// <summary>

/// 负责更新UI界面中时间显示的函数

/// </summary>

private void updateCurrentTime()

{

currentTime.Text = DateTime.Now.ToLongTimeString();

}

/// <summary>

/// 负责更新UI界面中随机数显示的函数

/// </summary>

/// <param name="numbers"></param>

private void updateRandomNumbers(int [] numbers)

{

System.Text.StringBuilder sb = new System.Text.StringBuilder();

foreach(int i in numbers)

sb.Append(i.ToString()).Append(", ");

randomNumbers.Text = sb.ToString();

}

private void Form1_Closing(object sender, System.ComponentModel.CancelEventArgs e)

{

if( (randomNumbersThread.ThreadState & ThreadState.Running) == ThreadState.Running )

randomNumbersThread.Abort();

randomNumbersThread = null;

if( (currentTimeThread.ThreadState & ThreadState.Running) == ThreadState.Running )

currentTimeThread.Abort();

currentTimeThread = null;

}

public delegate void UpdateTimeDelegate();

public delegate void UpdateRandomNumbers(int [] numbers);

}

   其实在C# 2.0 中所有的Control类都有Invoke()方法，如果负责更新UI元素的函数不是定义在Main()中，那么必须首先检测Control类中的InvokeRequired属性。举个例子吧，注意setProgressBarValue()函数中调用自己的方式.
        //在工作线程中更新主窗口进度条
        public void setProgressBarValue(ProgressBar progressBar1,int value)
        {
            if (progressBar1.InvokeRequired)
            {
                object[] parameters = new object[] { value };
                progressBar1.Invoke(new setProgressBarValueDelegate(setProgressBarValue), parameters);
            }
            else
                progressBar1.Value = value;
        }
这里的一些代码参考了http://www.codeproject.com 的例子.