下面double-buffer in gdi+程序中，是如何控制刷新的速度的？

Question

这个网页http://blog.csdn.net/Knight94/archive/2006/08/18/1094078.aspx中，博主是怎么控制这个刷新速度的？能让它再快一些吗？

Answer 1

帖子不能沉，各位帮帮忙吧
那个程序中，除了system.thread.sleep(400)控制了点时间，还有哪里控制时间的啊？这个刷新速度实在是看不出来

Answer 2

        public void DrawGraph()        {            while( !blnStop )            {                Thread.Sleep( 400 );                                if( blnStop ) break;                 //Redraw bitmap                RedrawImage();                 //Refresh pictorebox                try                {                    frmParent.Invoke( pHandler );                }                catch{ break;}            }        }
他那段代码关键就这里么，那你把这个400改小点不就刷新快点了。他是开个线程负责绘制到一个位图上，然后更新到界面上。

Answer 3

不过他没考虑并发的情况。如果加上一个IsDrawing在那个类里就比较好了。

Answer 4

呵呵，终于有人回了！
楼上的，怎么加这个IsDrawing？加在哪？谢谢

Answer 5

那我贴来吧。稍微的修改一下，对于我们的非游戏编程（不适用游戏引擎方式主动更新界面的情况），可能屏幕会因为遮挡而重绘，则可以这样加一个IsDrawing的标记来避免并发，并且，如果不加这个，他线程中的Sleep时间越短，并发操作可能越大。加这个就没问题了。代码如下：

Answer 6

//--------------------------- A Demo using Double-Buffer in GDI+ -------------------------------
//----------------------------------------------------------------------------------------------
//---File:      frmGraphView
//---Description:   A demo using double-buffer in GDI+
//---Author:    Knight
//---Date:      Jul.3, 2006
//----------------------------------------------------------------------------------------------
//---------------------------{A Demo using Double-Buffer in GDI+}-------------------------------
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Threading;
 
namespace GraphView
{
/// <summary>
/// Summary description for Form1.
/// </summary>
public class frmGraphView : System.Windows.Forms.Form
{
    private System.Windows.Forms.PictureBox picGraph;
    /// <summary>
    /// Required designer variable.
    /// </summary>
    private System.ComponentModel.Container components = null;
 
    private clsDrawThread myDrawThread = null;
    private Thread thdDraw = null;
    public frmGraphView()
    {
        //
        // Required for Windows Form Designer support
        //
        InitializeComponent();
 
        //
        // TODO: Add any constructor code after InitializeComponent call
        //
    }
 
    /// <summary>
    /// Clean up any resources being used.
    /// </summary>
    protected override void Dispose( bool disposing )
    {
        if( disposing )
        {
            if (components != null) 
            {
                components.Dispose();
            }
        }
        base.Dispose( disposing );
    }
 
    #region Windows Form Designer generated code
    /// <summary>
    /// Required method for Designer support - do not modify
    /// the contents of this method with the code editor.
    /// </summary>
    private void InitializeComponent()
    {
        this.picGraph = new System.Windows.Forms.PictureBox();
        this.SuspendLayout();
        // 
        // picGraph
        // 
        this.picGraph.BackColor = System.Drawing.Color.Black;
        this.picGraph.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D;
        this.picGraph.Dock = System.Windows.Forms.DockStyle.Fill;
        this.picGraph.Location = new System.Drawing.Point(0, 0);
        this.picGraph.Name = "picGraph";
        this.picGraph.Size = new System.Drawing.Size(498, 375);
        this.picGraph.TabIndex = 0;
        this.picGraph.TabStop = false;
        this.picGraph.Paint += new System.Windows.Forms.PaintEventHandler(this.picGraph_Paint);
        // 
        // frmGraphView
        // 
        this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
        this.ClientSize = new System.Drawing.Size(498, 375);
        this.Controls.Add(this.picGraph);
        this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedSingle;
        this.MaximizeBox = false;
        this.Name = "frmGraphView";
        this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
        this.Text = "Graph View";
        this.Closing += new System.ComponentModel.CancelEventHandler(this.frmGraphView_Closing);
        this.Load += new System.EventHandler(this.frmGraphView_Load);
        this.ResumeLayout(false);
 
    }
    #endregion
 
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main() 
    {
        Application.Run(new frmGraphView());
    }
 
    private void frmGraphView_Load(object sender, System.EventArgs e)
    {
        // Create thread class
        myDrawThread = new clsDrawThread( this, new DrawHandler( RefreshPictureBox ),
            picGraph.ClientSize.Width, picGraph.ClientSize.Height );
 
        // Start sub thread to draw
        thdDraw = new Thread( new ThreadStart( myDrawThread.DrawGraph ) );
        thdDraw.Start();
    }
 
 
    private void RefreshPictureBox()
    {
        // Refresh picturebox
        picGraph.Invalidate( picGraph.Region );
    }
 
    private void frmGraphView_Closing(object sender, System.ComponentModel.CancelEventArgs e)
    {
        // Close thread
        myDrawThread.IsStop = true;
        thdDraw.Join( 1 );
    }
 
    private void picGraph_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
    {
if(myDrawThread.IsDrawing) return;
        // Draw image
        e.Graphics.DrawImage( myDrawThread.DrawImage, 
            picGraph.ClientRectangle,
            picGraph.ClientRectangle,
            GraphicsUnit.Pixel );
    }
}
 
public delegate void DrawHandler();
public class clsDrawThread
{
    private Bitmap bitGraph = null;
    private bool blnStop = false;
    private int nStartY = -1;
    private int nEndY = -1;
    private Random ranPoint = null;
 
    private int nWidth = 0;
    private int nHeight = 0;
    private Form frmParent;
    private DrawHandler pHandler = null;
    public IsDrawing = false;
 
    /// <summary>
    /// Constructor
    /// </summary>
    /// <param name="pParent"></param>
    /// <param name="Handler"></param>
    /// <param name="Width"></param>
    /// <param name="Height"></param>
    public clsDrawThread( Form pParent, DrawHandler Handler, int Width, int Height )
    {
        // Init class member
        nWidth = Width;
        nHeight = Height;
 
        frmParent = pParent;//Parent form
        pHandler = Handler;//Call back delegate
 
        // Create double buffer
        bitGraph = new Bitmap( nWidth, nHeight );
 
        ranPoint = new Random( nHeight );//Create random
    }
 
    public bool IsStop
    {
        set{ blnStop = value;}
    }
 
    public Image DrawImage
    {
        get{ return bitGraph;}
    }
 
    /// <summary>
    /// Sub thread entry function
    /// </summary>
    public void DrawGraph()
    {
        while( !blnStop )
        {
            Thread.Sleep( 400 );
            
            if( blnStop ) break;
 
            //Redraw bitmap
    IsDrawing = true;
            RedrawImage();
    IsDrawing = false;
 
            //Refresh pictorebox
            try
            {
                frmParent.Invoke( pHandler );
            }
            catch{ break;}
        }
    }
 
    /// <summary>
    /// Re-draw image
    /// </summary>
    private void RedrawImage()
    {
        const int CLIP_WIDTH = 10;
        Bitmap bitNew = new Bitmap( nWidth, nHeight );
        Graphics gImage = Graphics.FromImage( bitNew );
 
        // Use black color to fill the entire rectangle 
        gImage.FillRectangle( new SolidBrush( Color.Black ), 
            new Rectangle( new Point( 0, 0), 
            new Size( nWidth, nHeight ) ) );
 
        // Copy image from source image
        gImage.DrawImage( bitGraph, 
            new Rectangle( 0,0, nWidth - CLIP_WIDTH, nHeight ),
            new Rectangle( CLIP_WIDTH,0, nWidth - CLIP_WIDTH, nHeight ),
            GraphicsUnit.Pixel );
            
        // Draw new clip image
        if( nStartY < 0 )
            nStartY = ranPoint.Next() % nHeight;
        else
            nStartY = nEndY;
        nEndY = ranPoint.Next() % nHeight;
 
        // Draw new line
        gImage.DrawLine( new Pen( Color.Red, 1.5f ), 
            new Point( nWidth - CLIP_WIDTH, nStartY ),
            new Point( nWidth - 1, nEndY ) );
 
        // Set new image and release old image
        Bitmap bitOld = bitGraph;
        bitGraph = bitNew;
        bitOld.Dispose();
    }
 
}
}