/*
 *  File: Converter.java
 *  Author: Java, Java, Java
 *  Description:  This version of the Converter class 
 *   presents a more elaborate GUI for interacting with
 *   the MetricConverter class. In the previous version
 *   the user had to type in their input. In this version
 *   a numeric key pad is used to input miles.
 
 *  Note: One shortcoming with the interface for this version
 *   is that it uses a FlowLayout for the keypad. It should
 *   use a GridLayout to arrange the buttons into a two-dimensional
 *   array.
 */

import javax.swing.*;      // Packages used 
import java.awt.*;
import java.awt.event.*;

public class Converter extends JFrame implements ActionListener{ // Version 2

    private final static int NBUTTONS = 12;  

    private JLabel prompt = new JLabel("Distance in miles: "); 
    private JTextField input = new JTextField(6);
    private JTextArea display = new JTextArea(10,20);
    private JButton convert = new JButton("Convert!");
    private JPanel keypadPanel = new JPanel();
  
    private JButton keyPad[];           // An array of buttons
    private String label[] =            // An array of button labels
                { "1","2","3",
                  "4","5","6",
                  "7","8","9",
                  "C","0","." };

    /**
     *  Converter() constructor sets the layout and adds
     *  components to the top-level JFrame. Note that components
     *  are added to the ContentPane rather to the JFrame itself.
     */
    public Converter () {
        getContentPane().setLayout( new FlowLayout() ); 
        initKeyPad();
        getContentPane().add(prompt);
        getContentPane().add(input);
        getContentPane().add(convert);  
        getContentPane().add(display);
        getContentPane().add(keypadPanel);
        display.setLineWrap( true );
        display.setEditable( false );
    
        convert.addActionListener(this);   
        input.addActionListener(this);
    } // Converter()
  
    /**
     *  initKeyPad() creates an array of JButtons and organizes them
     *   into a graphical key pad panel. Note that you must distinguish
     *   the JButton array, an internal memory structure, from the 
     *   key pad panel, a graphical object that appears in the user interface.
     */
    public void initKeyPad() {   
        keyPad = new JButton[NBUTTONS];             // Create the array itself
        for(int k = 0; k < keyPad.length; k++) {    // For each button
            keyPad[k] = new JButton(label[k]);      //  Create a labeled button
            keyPad[k].addActionListener(this);      //  and a listener
            keypadPanel.add(keyPad[k]);             //  and add it to the panel
        } // for
    } // initKeyPad()

    /**
     *  actionPerformed() handles all action events for the program.
     *   It must distinguish whether the user clicked on what of the
     *   buttons on the keypad or on the "Convert" or "Input" button.
     *  @param e -- the ActionEvent which prompted this method call
     */
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == convert || e.getSource() == input) {
            double miles = Double.valueOf(input.getText()).doubleValue();
            double km = MetricConverter.milesToKm(miles);
            display.append(miles + " miles equals " + km + " kilometers\n");
            input.setText("");
        } else {                                 // A keypad button was pressed
            JButton b = (JButton)e.getSource();
            if (b.getText().equals("C"))
                input.setText("");                   
            else
                input.setText( input.getText() + b.getText() );     
        }
    } // actionPerformed()

    /**
     *  main() creates an instance of this (Converter) class and sets
     *   the size and visibility of its JFrame. 
     *  An anonymous class is used to create an instance of the 
     *   WindowListener class, which handles the window close events
     *   for the application.
     */
    public static void main(String args[]) {
        Converter f = new Converter();
        f.setSize(400, 300);  
        f.setVisible(true);
        f.addWindowListener(new WindowAdapter() {      // Quit the application
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
    } // main()
} // Converter

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/*
 *  File: MetricConverter.java
 *  Author: Java, Java, Java
 *  Description: This class implements the static milesToKm()
 *    method, which converts miles to kilometers.
 */

public class MetricConverter {

    /**
     *  mileToKm() converts miles to kilometers
     *  @param miles -- the number of miles to convert
     *  @return -- a double giving the number of kilometers
     */
    public static double milesToKm(double miles) {
        return miles / 0.62;
    }
}