9.20-radiobuttondemo.java

介绍有关java的资料 课件 相当一本书籍 里面都是很基础的知识

// RadioButtonDemo.java: Use radio buttons to select a choice
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class RadioButtonDemo extends JFrame implements ItemListener
{
  // Declare radio buttons
  private JRadioButton jrbRed, jrbYellow, jrbGreen;

  // Declare a radio button group
  private ButtonGroup btg = new ButtonGroup();

  // Declare a traffic light display panel
  private Light light;

  // Main method
  public static void main(String[] args)
  {
    RadioButtonDemo frame = new RadioButtonDemo();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(250, 170);
    frame.setVisible(true);
  }

  // Constructor
  public RadioButtonDemo()
  {
    setTitle("RadioButton Demo");

    // Add traffic light panel to panel p1
    JPanel p1 = new JPanel();
    p1.setSize(200, 200);
    p1.setLayout(new FlowLayout(FlowLayout.CENTER));
    light = new Light();
    light.setSize(40, 90);
    p1.add(light);

    // Put the radio button in Panel p2
    JPanel p2 = new JPanel();
    p2.setLayout(new FlowLayout());
    p2.add(jrbRed = new JRadioButton("Red", false));
    p2.add(jrbYellow = new JRadioButton("Yellow", false));
    p2.add(jrbGreen = new JRadioButton("Green", false));

    // Set keyboard mnemonics
    jrbRed.setMnemonic('R');
    jrbYellow.setMnemonic('Y');
    jrbGreen.setMnemonic('G');
    
    // Group radio buttons
    btg.add(jrbRed);
    btg.add(jrbYellow);
    btg.add(jrbGreen);

    // Place p1 and p2 in the frame
    getContentPane().setLayout(new BorderLayout());
    getContentPane().add(p1, BorderLayout.CENTER);
    getContentPane().add(p2, BorderLayout.SOUTH);

    // Register listeners for check boxes
    jrbRed.addItemListener(this);
    jrbYellow.addItemListener(this);
    jrbGreen.addItemListener(this);
  }

  // Handle checkbox events
  public void itemStateChanged(ItemEvent e)
  {
    if (jrbRed.isSelected())
      light.turnOnRed(); // Set red light
    if (jrbYellow.isSelected())
      light.turnOnYellow(); // Set yellow light
    if (jrbGreen.isSelected())
      light.turnOnGreen(); // Set green light
  }
}

// Three traffic lights shown in a panel
class Light extends JPanel
{
  private boolean red;
  private boolean yellow;
  private boolean green;

  public Light()
  {
    red = false;
    yellow = false;
    green = false;
  }

  // Set red light on
  public void turnOnRed()
  {
    red = true;
    yellow = false;
    green = false;
    repaint();
  }

  // Set yellow light on
  public void turnOnYellow()
  {
    red = false;
    yellow = true;
    green = false;
    repaint();
  }

  // Set green light on
  public void turnOnGreen()
  {
    red = false;
    yellow = false;
    green = true;
    repaint();
  }

  // Display lights
  public void paintComponent(Graphics g)
  {
    super.paintComponent(g);

    if (red)
    {
      g.setColor(Color.red);
      g.fillOval(10, 10, 20, 20);
      g.setColor(Color.black);
      g.drawOval(10, 35, 20, 20);
      g.drawOval(10, 60, 20, 20);
      g.drawRect(5, 5, 30, 80);
    }
    else if (yellow)
    {
      g.setColor(Color.yellow);
      g.fillOval(10, 35, 20, 20);
      g.setColor(Color.black);
      g.drawRect(5, 5, 30, 80);
      g.drawOval(10, 10, 20, 20);
      g.drawOval(10, 60, 20, 20);
    }
    else if (green)
    {
      g.setColor(Color.green);
      g.fillOval(10, 60, 20, 20);
      g.setColor(Color.black);
      g.drawRect(5, 5, 30, 80);
      g.drawOval(10, 10, 20, 20);
      g.drawOval(10, 35, 20, 20);
    }
    else
    {
      g.setColor(Color.black);
      g.drawRect(5, 5, 30, 80);
      g.drawOval(10, 10, 20, 20);
      g.drawOval(10, 35, 20, 20);
      g.drawOval(10, 60, 20, 20);
    }
  }

  // Set preferred size
  public Dimension getPreferredSize()
  {
    return new Dimension(40, 90);
  }
}