fahrenheitpanel.java

Java 程序设计教程（第五版）EXAMPLESchap04源码

//********************************************************************
//  FahrenheitPanel.java       Author: Lewis/Loftus
//
//  Demonstrates the use of text fields.
//********************************************************************

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

public class FahrenheitPanel extends JPanel
{
   private JLabel inputLabel, outputLabel, resultLabel;
   private JTextField fahrenheit;

   //-----------------------------------------------------------------
   //  Constructor: Sets up the main GUI components.
   //-----------------------------------------------------------------
   public FahrenheitPanel()
   {
      inputLabel = new JLabel ("Enter Fahrenheit temperature:");
      outputLabel = new JLabel ("Temperature in Celsius: ");
      resultLabel = new JLabel ("---");

      fahrenheit = new JTextField (5);
      fahrenheit.addActionListener (new TempListener());

      add (inputLabel);
      add (fahrenheit);
      add (outputLabel);
      add (resultLabel);

      setPreferredSize (new Dimension(300, 75));
      setBackground (Color.yellow);
   }

   //*****************************************************************
   //  Represents an action listener for the temperature input field.
   //*****************************************************************
   private class TempListener implements ActionListener
   {
      //--------------------------------------------------------------
      //  Performs the conversion when the enter key is pressed in
      //  the text field.
      //--------------------------------------------------------------
      public void actionPerformed (ActionEvent event)
      {
         int fahrenheitTemp, celsiusTemp;

         String text = fahrenheit.getText();

         fahrenheitTemp = Integer.parseInt (text);
         celsiusTemp = (fahrenheitTemp-32) * 5/9;

         resultLabel.setText (Integer.toString (celsiusTemp));
      }
   }
}