select.java

Java 入门书的源码

//Copyright (c) 1998, Arthur Gittleman
//This example is provided WITHOUT ANY WARRANTY either expressed or implied.

/* Uses a choice box to choose a color, and
 * two checkboxes to choose a shape. Uses a draw button
 * to request drawing the selected shape in the
 * selected color.
 */

import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;

public class Select extends Applet {
  Button draw = new Button("Draw");
  DrawOn canvas = new DrawOn();
  Choice color = new Choice();
  CheckboxGroup shapes = new CheckboxGroup();
  Checkbox square = new Checkbox("Square",false,shapes);
  Checkbox circle = new Checkbox("Circle",true,shapes);
  Color [] theColor = {Color.red,Color.green,Color.blue};
  String [] colorName = {"Red","Green","Blue"};

  public void init() {
    add(draw);
    add(color);
    add(square);
    add(circle);
    add(canvas);
    for (int i=0; i<colorName.length; i++) 
      color.add(colorName[i]);
    color.select(0);
    canvas.setSize(150,150);
    draw.addActionListener(canvas);
  }

  class DrawOn extends Canvas implements ActionListener {
    public void actionPerformed(ActionEvent event) {
      repaint();
    }
    public void paint(Graphics g) {
      g.setColor(theColor[color.getSelectedIndex()]);
      if (circle.getState())
         g.fillOval(20,20,100,100);
      else
         g.fillRect(20,20,100,100);
    }   
  }
}