exercise24_3.java

来自「java程序设计 机械工业出版社 书籍代码」· Java 代码 · 共 58 行

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

public class Exercise24_3 extends JApplet {
  // Create a JSpinner
  private JSpinner spinner =
    new JSpinner(new ReverseSpinnerNumberModel());

  // Create a JLabel
  private JLabel label = new JLabel("", JLabel.CENTER);

  public Exercise24_3() {
    // Add spinner and label to the UI
    getContentPane().add(spinner, BorderLayout.NORTH);
    getContentPane().add(label, BorderLayout.CENTER);

    // Register and create a listener
    spinner.addChangeListener(new ChangeListener() {
      public void stateChanged(javax.swing.event.ChangeEvent e) {
        label.setText("Previous value: " + spinner.getPreviousValue()
          + " Current value: " + spinner.getValue()
          + " Next value: " + spinner.getNextValue());
      }
    });
  }

  public static void main(String[] args) {
    javax.swing.JFrame frame = new javax.swing.JFrame(
        "Exercise24_3");

    Exercise24_3 applet = new Exercise24_3();

    // Add the applet instance to the frame
    frame.getContentPane().add(applet, java.awt.BorderLayout.CENTER);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // Invoke init and start
    applet.init();
    applet.start();

    // Display the frame
    frame.setSize(300, 300);
    frame.setVisible(true);
  }
}

class ReverseSpinnerNumberModel extends SpinnerNumberModel {
  private int value = 2;

  public Object getPreviousValue() {
    return super.getNextValue();
  }

  public Object getNextValue() {
    return super.getPreviousValue();
  }
}