麻烦各位大虾帮我分析下下面的代码，就是运行程序后在界面画了几条线，然后把它最小化后又最大化，怎么原先画的几条线没有重绘出来

Question

import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
import java.util.*;
public class DrawLine1 extends Frame 
 {
  Image oimg = null;
  Graphics og = null;
  int orgX;
int orgY;
int endX;
int endY;
  public void paint(Graphics g)
  {
  g.drawImage(oimg,0,0,this);
  }
public DrawLine1()
{
setSize(400,400);
setTitle("DrawLine1");
setVisible(true);

Dimension d = getSize();
Image oimg = createImage(d.width,d.height);
Graphics og = oimg.getGraphics();

addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
dispose();
System.exit(0);
}
});

this.addMouseListener(new MouseAdapter()
{

public void mousePressed(MouseEvent e)
{
orgX = e.getX();
orgY = e.getY();

}
public void mouseReleased(MouseEvent e)
{
endX = e.getX();
endY = e.getY();
Graphics og = getGraphics();
og.setColor(Color.RED);
og.setFont(new Font("null",Font.ITALIC|Font.BOLD,30));
og.drawLine(orgX,orgY,e.getX(),e.getY());
og.drawString(orgX + "," + orgY,orgX,orgY);
og.drawString(e.getX() + "," + e.getY(),e.getX(),e.getY());

}
});
}

public static void main(String[] args) {

DrawLine1 mainFrame = new DrawLine1();

}
}

Answer 1

1,窗口的一些动作是需要重绘的,所以我们需要保存某些状态/**
 * CSND-画线
 * @version 2012-2-25
 */
public class DrawLine1 extends Frame {
    /** 存储LineModel */
    private List<LineModel> lineModelArr = new ArrayList<LineModel>();
    private Image oimg = null;
    private Graphics og = null;
    private int orgX;
    private int orgY;    /**
     * Constructor
     */
    public DrawLine1() {
        setSize(400, 400);
        setTitle("DrawLine1");
        setVisible(true);        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                dispose();
                System.exit(0);
            }
        });        this.addMouseListener(new MouseAdapter() {            public void mousePressed(MouseEvent e) {
                orgX = e.getX();
                orgY = e.getY();            }            public void mouseReleased(MouseEvent e) {
                Graphics og = getGraphics();
                og.setColor(Color.RED);
                og.setFont(new Font("null", Font.ITALIC | Font.BOLD, 30));
                LineModel lmInst = new LineModel(orgX, orgY, e.getX(), e.getY());
                lmInst.drawLine(og);
                lineModelArr.add(lmInst);
                // og.drawLine(orgX, orgY, e.getX(), e.getY());
                og.drawString(orgX + "," + orgY, orgX, orgY);
                og.drawString(e.getX() + "," + e.getY(), e.getX(), e.getY());
            }
        });
    }    /*
     * (non-Javadoc)
     * @see java.awt.Container#paintComponents(java.awt.Graphics)
     */
    @Override
    public void paint(Graphics g) {
        super.paint(g);
        for (Iterator<LineModel> iterator = lineModelArr.iterator(); iterator.hasNext();) {
            iterator.next().drawLine(g);
        }
    }    /**
     * 测试入口
     * @param args 参数列表
     */
    public static void main(String[] args) {
        DrawLine1 mainFrame = new DrawLine1();
    }    /**
     * 抽象画线模型
     * @author WangYanCheng
     * @version 2012-2-25
     */
    private class LineModel {
        /** 存储坐标 */
        private int fX, fY, sX, sY;        /**
         * Constructor
         * @param orgX
         * @param orgY
         * @param endX
         * @param endY
         */
        public LineModel(int orgX, int orgY, int endX, int endY) {
            this.fX = orgX;
            this.fY = orgY;
            this.sX = endX;
            this.sY = endY;
        }        /**
         * 绘制
         * @param g Graphics
         */
        public void drawLine(Graphics g) {
            g.drawLine(fX, fY, sX, sY);
        }
    }
}