import javax.swing.JFrame;
import java.awt.Canvas;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionAdapter;
import java.awt.event.MouseMotionListener;
import java.awt.event.MouseEvent;
import java.awt.Color;

public class Line extends JFrame {
private int startx,starty,endx,endy;
private Canvas can;/画布
public Line(){

super("line");
this.setSize(300,300);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
can=new Canvas();
getContentPane().add(can);
can.addMouseListener(new MouseAdapter(){
public void mousePressed(MouseEvent e){
startx=e.getX();
starty=e.getY();

}
public void mouseReleased(MouseEvent e){
can.getGraphics().setColor(Color.green);
can.getGraphics().drawLine(startx,starty,endx,endy);

}
});
can.addMouseMotionListener(new MouseMotionAdapter(){
public void mouseDragged(MouseEvent e){//点下左键 拖动松开可出现直线
endx=e.getX();
endy=e.getY();

}

});
}

public static void main(String args[]){
new Line().setVisible(true);
}
}

paint(Graphics g);方法的 不用注释能看懂吧

import javax.swing.JFrame;


import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionAdapter;
import java.awt.event.MouseMotionListener;
import java.awt.event.MouseEvent;
import java.awt.Color;

public class Line extends JFrame {
private int startx,starty,endx,endy,oldx,oldy,old_x,old_y;

public Line(){

super("line");
this.setSize(300,300);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

this.addMouseListener(new MouseAdapter(){
public void mousePressed(MouseEvent e){
startx=e.getX();
starty=e.getY();
oldx=startx;
oldy=starty;

}
public void mouseReleased(MouseEvent e){
repaint();

}
});
this.addMouseMotionListener(new MouseMotionAdapter(){
public void mouseDragged(MouseEvent e){//点下左键 拖动可出现直线
endx=e.getX();
endy=e.getY();
old_x=endx;
old_y=endy;
repaint();


}

});
}
public void paint(Graphics g){
super.paint(g);
g.setColor(this.getBackground());
g.drawLine(oldx,oldy,old_x,old_y);
g.setColor(Color.green);
g.drawLine(startx,starty,endx,endy);
}

public static void main(String args[]){
new Line().setVisible(true);
}
}

连千里老大也这么说
呵呵
看来真的思考下了

努力学习中!我也大三了,马上也要找工作了,心里还没底啊

惭愧啊 刚看了个开源论坛 人家那东西写的 哎 学一年半载也进不了门啊:)还是大家继续努力吧

好厉害。刚开始学。先顶一个了。

我觉得这个帖子应该是精华贴 应该置顶啊

有MM这么说 真实荣幸啊

谢谢 楼主的资源共享了 呵呵

呵,我正要那个做计算器的.先谢了啊,下下来借鉴一下.