画的图最小化后怎么就没有了？

Question

拜托了
我是小鸟，分都问完了

Answer 1

是不是刷新一下就没了? 我对GUI也不太懂, 下面的是以前的一个作业, 画直线, 希望能对楼主有说帮助using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;namespace 画直线_Demo_02101434_陈剑
{
/// <summary>
/// Form1 的摘要说明。
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
        private System.Windows.Forms.PictureBox picDrawLine;
        private Pen myPen;
        private bool drawState;
        private Graphics gTemp;
        private Graphics g;
        private int x, y;
        private int xD, yD;            /// <summary>
/// 必需的设计器变量。
/// </summary>
private System.ComponentModel.Container components = null; public Form1()
{
//
// Windows 窗体设计器支持所必需的
//
InitializeComponent(); //
// TODO: 在 InitializeComponent 调用后添加任何构造函数代码
//
} /// <summary>
/// 清理所有正在使用的资源。
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null) 
{
components.Dispose();
}
}
base.Dispose( disposing );
} #region Windows 窗体设计器生成的代码
/// <summary>
/// 设计器支持所需的方法 - 不要使用代码编辑器修改
/// 此方法的内容。
/// </summary>
private void InitializeComponent()
{
            System.Resources.ResourceManager resources = new System.Resources.ResourceManager(typeof(Form1));
            this.picDrawLine = new System.Windows.Forms.PictureBox();
            this.SuspendLayout();
            // 
            // picDrawLine
            // 
            this.picDrawLine.BackColor = System.Drawing.Color.White;
            this.picDrawLine.Image = ((System.Drawing.Image)(resources.GetObject("picDrawLine.Image")));
            this.picDrawLine.Location = new System.Drawing.Point(5, 5);
            this.picDrawLine.Name = "picDrawLine";
            this.picDrawLine.Size = new System.Drawing.Size(370, 305);
            this.picDrawLine.TabIndex = 0;
            this.picDrawLine.TabStop = false;
            this.picDrawLine.MouseUp += new System.Windows.Forms.MouseEventHandler(this.picDrawLine_MouseUp);
            this.picDrawLine.MouseMove += new System.Windows.Forms.MouseEventHandler(this.picDrawLine_MouseMove);
            this.picDrawLine.MouseDown += new System.Windows.Forms.MouseEventHandler(this.picDrawLine_MouseDown);
            // 
            // Form1
            // 
            this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
            this.ClientSize = new System.Drawing.Size(377, 315);
            this.Controls.Add(this.picDrawLine);
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedDialog;
            this.Name = "Form1";
            this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
            this.Text = "画直线_Demo_02101434_陈剑";
            this.Load += new System.EventHandler(this.Form1_Load);
            this.ResumeLayout(false);        }
#endregion /// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main() 
{
Application.Run(new Form1());
}        private void Form1_Load(object sender, System.EventArgs e)
        {
            gTemp = this.picDrawLine.CreateGraphics();
            myPen = new Pen(Brushes.Blue, 2);
            g = System.Drawing.Graphics.FromImage(this.picDrawLine.Image);
        }        private void picDrawLine_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
        {
            drawState = true;
            xD = x = e.X;
            yD = y = e.Y;
        }        private void picDrawLine_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
        {
            if (drawState == true)
            {
                gTemp.DrawLine(new Pen(Brushes.White, 2), x, y, xD, yD);
                
                gTemp.DrawLine(myPen, x, y, e.X, e.Y);
                this.Refresh();
                xD = e.X;
                yD = e.Y;
                
                //this.picDrawLine.Image.Save("paint.bmp");
//                this.picDrawLine.BackgroundImage.Save("paint.bmp");
            }
        }        private void picDrawLine_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e)
        {
            if (drawState == true)
            {
                drawState = false;
                g.DrawLine(myPen, x, y, e.X, e.Y);
                //gTemp.Clear(Color.White);
                this.Refresh();
            }
        }
}
}

Answer 2

你应该在paint事件中绘制，这样最小化后再还原时，会重新绘制

Answer 3

重写OnPaint 把绘制操作写在当中