C#后台線程和UI的交互

在C#中，從Main()方法開始一個默認的線程，一般稱之為主線程，如果在這個進行一些非常耗CPU的計算，那么UI界面就會被掛起而處於假死狀態，也就是說無法和用戶進行交互了，特別是要用類似進度條來實時顯示一些提示信息的時候，這種情況就顯得很糟糕。如果多開一些線程來完成一些耗時的計算，那么工作線程也是無法如此更新UI界面中的元素的，比如直接顯示一個提示信息：label1.Text=outstring，原因很簡單UI屬於默認的主線程，而線程間是不能這樣直接訪問彼此的成員的。
如果要解決以上的兩個問題，那么可以借助C#中的Delegate和控件類中的Invoke()方法來搞定。
這里給出的例子比較簡單，主要思路是：在Main()中啟動其它的線程作為后台進程，其中一個線程是實時顯示當前的時間，一個線程是顯示一些隨機數，這樣一來三個線程同時運行，彼此通過代理來聯系。
紅色代碼精華

 

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();
            
            //創建新的工作線程
            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設計#region UI設計
        private void InitializeComponent()
        {
            this.label1 = new System.Windows.Forms.Label();
            this.currentTime = new System.Windows.Forms.TextBox();
            this.label2 = new System.Windows.Forms.Label();
            this.randomNumbers = new System.Windows.Forms.TextBox();
            this.threadManager = new System.Windows.Forms.GroupBox();
            this.manageBoth = new System.Windows.Forms.RadioButton();
            this.manageNumbers = new System.Windows.Forms.RadioButton();
            this.manageTime = new System.Windows.Forms.RadioButton();
            this.pause = new System.Windows.Forms.Button();
            this.stop = new System.Windows.Forms.Button();
            this.start = new System.Windows.Forms.Button();
            this.threadManager.SuspendLayout();
            this.SuspendLayout();
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(8, 24);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(79, 13);
            this.label1.TabIndex = 0;
            this.label1.Text = "現在的時間：";
            // 
            // currentTime
            // 
            this.currentTime.Location = new System.Drawing.Point(88, 23);
            this.currentTime.Name = "currentTime";
            this.currentTime.ReadOnly = true;
            this.currentTime.Size = new System.Drawing.Size(157, 20);
            this.currentTime.TabIndex = 1;
            // 
            // label2
            // 
            this.label2.AutoSize = true;
            this.label2.Location = new System.Drawing.Point(14, 56);
            this.label2.Name = "label2";
            this.label2.Size = new System.Drawing.Size(43, 13);
            this.label2.TabIndex = 2;
            this.label2.Text = "隨機數";
            // 
            // randomNumbers
            // 
            this.randomNumbers.Location = new System.Drawing.Point(16, 72);
            this.randomNumbers.Name = "randomNumbers";
            this.randomNumbers.ReadOnly = true;
            this.randomNumbers.Size = new System.Drawing.Size(229, 20);
            this.randomNumbers.TabIndex = 3;
            // 
            // threadManager
            // 
            this.threadManager.Controls.Add(this.manageBoth);
            this.threadManager.Controls.Add(this.manageNumbers);
            this.threadManager.Controls.Add(this.manageTime);
            this.threadManager.Controls.Add(this.pause);
            this.threadManager.Controls.Add(this.stop);
            this.threadManager.Controls.Add(this.start);
            this.threadManager.Location = new System.Drawing.Point(16, 104);
            this.threadManager.Name = "threadManager";
            this.threadManager.Size = new System.Drawing.Size(229, 154);
            this.threadManager.TabIndex = 7;
            this.threadManager.TabStop = false;
            this.threadManager.Text = "工作線程控制";
            // 
            // manageBoth
            // 
            this.manageBoth.Location = new System.Drawing.Point(34, 74);
            this.manageBoth.Name = "manageBoth";
            this.manageBoth.Size = new System.Drawing.Size(104, 16);
            this.manageBoth.TabIndex = 12;
            this.manageBoth.Text = "同時運行";
            this.manageBoth.CheckedChanged += new System.EventHandler(this.manageBoth_CheckedChanged);
            // 
            // manageNumbers
            // 
            this.manageNumbers.Location = new System.Drawing.Point(34, 50);
            this.manageNumbers.Name = "manageNumbers";
            this.manageNumbers.Size = new System.Drawing.Size(104, 16);
            this.manageNumbers.TabIndex = 11;
            this.manageNumbers.Text = "更新隨機數線程";
            this.manageNumbers.CheckedChanged += new System.EventHandler(this.manageNumbers_CheckedChanged);
            // 
            // manageTime
            // 
            this.manageTime.Location = new System.Drawing.Point(34, 26);
            this.manageTime.Name = "manageTime";
            this.manageTime.Size = new System.Drawing.Size(104, 16);
            this.manageTime.TabIndex = 10;
            this.manageTime.Text = "更新時間線程";
            this.manageTime.CheckedChanged += new System.EventHandler(this.manageTime_CheckedChanged);
            // 
            // pause
            // 
            this.pause.Location = new System.Drawing.Point(84, 115);
            this.pause.Name = "pause";
            this.pause.Size = new System.Drawing.Size(54, 23);
            this.pause.TabIndex = 9;
            this.pause.Text = "暫停";
            this.pause.Click += new System.EventHandler(this.pause_Click);
            // 
            // stop
            // 
            this.stop.Location = new System.Drawing.Point(158, 115);
            this.stop.Name = "stop";
            this.stop.Size = new System.Drawing.Size(51, 23);
            this.stop.TabIndex = 8;
            this.stop.Text = "停止";
            this.stop.Click += new System.EventHandler(this.stop_Click);
            // 
            // start
            // 
            this.start.Location = new System.Drawing.Point(6, 115);
            this.start.Name = "start";
            this.start.Size = new System.Drawing.Size(50, 23);
            this.start.TabIndex = 7;
            this.start.Text = "開始";
            this.start.Click += new System.EventHandler(this.start_Click);
            // 
            // Form1
            // 
            this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
            this.ClientSize = new System.Drawing.Size(253, 271);
            this.Controls.Add(this.threadManager);
            this.Controls.Add(this.randomNumbers);
            this.Controls.Add(this.label2);
            this.Controls.Add(this.currentTime);
            this.Controls.Add(this.label1);
            this.Name = "Form1";
            this.Text = "工作線程和UI的交互";
            this.Closing += new System.ComponentModel.CancelEventHandler(this.Form1_Closing);
            this.threadManager.ResumeLayout(false);
            this.ResumeLayout(false);
            this.PerformLayout();
        }
        #endregion

        
        [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,其有兩種使用形式
        /// 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> /// 負責更新UI界面中時間顯示的函數 /// </summary> private void updateCurrentTime() { currentTime.Text = DateTime.Now.ToLongTimeString(); } /**//// <summary> /// 負責更新UI界面中隨機數顯示的函數 /// </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); }

　　   其實在C# 2.0 中所有的Control類都有Invoke()方法，如果負責更新UI元素的函數不是定義在Main()中，那么必須首先檢測Control類中的InvokeRequired屬性。舉個例子吧，注意setProgressBarValue()函數中調用自己的方式.

 //在工作線程中更新主窗口進度條
        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;
        }
  這里的一些代碼參考了http://www.codeproject.com  的例子.