jpaint2.java

刘艺编著的java教程的课本习题加例题代码 很有用哦！

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.*;
import javax.swing.event.*;

class DrawLine extends JPanel
{
  private int startX;
  private int startY;
  private int length;
  public DrawLine(int x,int y,int l)
  {
   this.setBackground(Color.lightGray);
   this.setForeground(Color.blue);
   startX=x;
   startY=y;
   length=l;
  }

  public void setLength(int l)
  {
   length=l;
   repaint();
  }

  public void paintComponent(Graphics g)
  {
   super.paintComponent(g);
   g.drawString("try to draw line",10,10);
   g.setColor(Color.red);
   g.drawLine(startX,startY,startX+length,startY);
  }
}


public class JPaint2 extends JApplet
{
  private DrawLine drawline1=new DrawLine(30,20,30);
  private JSlider adjustCycles = new JSlider(1, 100, 5);
  //Initialize the applet
  public void init()
  {
    Container cp=this.getContentPane();
    cp.add(drawline1);


    adjustCycles.addChangeListener(new ChangeListener() {
      public void stateChanged(ChangeEvent e) {
        drawline1.setLength(
          ((JSlider)e.getSource()).getValue());
      }
    });
    cp.add(BorderLayout.SOUTH, adjustCycles);
  }
}