Question

How can I make this program able to implement listener for the editable text field:

/////////////////////////////// KiloConverter.java //////////////////////////

import java.awt.BorderLayout;

import java.awt.Color;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JPanel;

import javax.swing.JTextField;

public class KiloConverter extends JFrame {

// constant for converting km to miles

static final double KM_TO_MILES = 0.6214;

// important components that needs to be accessed throughout the program

private JTextField input, output;

// constructor initializing GUI

public KiloConverter() {

// passing title to super class

super("Kilometer Converter");

// will exit on click

setDefaultCloseOperation(EXIT_ON_CLOSE);

// creating a panel

JPanel panel1 = new JPanel();

// creating components for first row, adding to the above panel

JLabel label1 = new JLabel("Enter a distance in kilometers");

input = new JTextField(15);

JButton calc = new JButton("Calculate");

panel1.add(label1);

panel1.add(input);

panel1.add(calc);

// creating another panel

JPanel panel2 = new JPanel();

// creating components for second row, adding to the above panel

output = new JTextField(15);

output.setEditable(false); // not editable

output.setBackground(Color.LIGHT_GRAY);

JLabel label2 = new JLabel("Miles");

JButton exit = new JButton("Exit");

panel2.add(output);

panel2.add(label2);

panel2.add(exit);

// adding first panel to the north of window, second to the south

add(panel1, BorderLayout.NORTH);

add(panel2, BorderLayout.SOUTH);

// adding action listeners to the buttons

calc.addActionListener(new CalculateButtonListener());

exit.addActionListener(new ExitButtonListener());

// using compact size

pack();

}

// private inner class representing action to be performed when calculate

// button is clicked

private class CalculateButtonListener implements ActionListener {

@Override

public void actionPerformed(ActionEvent e) {

// getting input, parsing to double, converting to miles, displaying

// with 3 digits precision

double km = Double.parseDouble(input.getText());

double miles = km * KM_TO_MILES;

output.setText(String.format("%.3f", miles));

}

}

// private inner class representing action to be performed when exit

// button is clicked

private class ExitButtonListener implements ActionListener {

@Override

public void actionPerformed(ActionEvent e) {

//simply exiting

System.exit(0);

}

}

}

// /////////////////////// Driver.java /////////////////////////////////

//public driver program to run the KiloConverter class

public class Driver {

public static void main(String[] args) {

KiloConverter converter = new KiloConverter();

converter.setVisible(true);

}

}

Answer 1

// KiloConverter.java

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class KiloConverter extends JFrame {

   // constant for converting km to miles

   static final double KM_TO_MILES = 0.6214;

   // important components that needs to be accessed throughout the program

   private JTextField input, output;

   // constructor initializing GUI

   public KiloConverter() {

   // passing title to super class

   super("Kilometer Converter");

   // will exit on click

   setDefaultCloseOperation(EXIT_ON_CLOSE);

   // creating a panel

   JPanel panel1 = new JPanel();

   // creating components for first row, adding to the above panel

   JLabel label1 = new JLabel("Enter a distance in kilometers");

   input = new JTextField(15);

   JButton calc = new JButton("Calculate");

   panel1.add(label1);

   panel1.add(input);

   panel1.add(calc);
  
   // creating another panel

   JPanel panel2 = new JPanel();

   // creating components for second row, adding to the above panel

   output = new JTextField(15);

   output.setEditable(false); // not editable

   output.setBackground(Color.LIGHT_GRAY);

   JLabel label2 = new JLabel("Miles");

   JButton exit = new JButton("Exit");

   panel2.add(output);

   panel2.add(label2);

   panel2.add(exit);

   // adding first panel to the north of window, second to the south

   add(panel1, BorderLayout.NORTH);

   add(panel2, BorderLayout.SOUTH);

   // adding action listeners to the buttons

   // adds action listener for the input textfield, so that after the user enters the input value and press enter, it calculates and displays the resultant value in output textfield

input.addActionListener(new CalculateButtonListener());
  
   calc.addActionListener(new CalculateButtonListener());

   exit.addActionListener(new ExitButtonListener());

   // using compact size

   pack();

   }
  
   // private inner class representing action to be performed when calculate

   // button is clicked

   private class CalculateButtonListener implements ActionListener {

   @Override

   public void actionPerformed(ActionEvent e) {

   // getting input, parsing to double, converting to miles, displaying

   // with 3 digits precision

   double km = Double.parseDouble(input.getText());

   double miles = km * KM_TO_MILES;

   output.setText(String.format("%.3f", miles));

   }

   }
  
   // private inner class representing action to be performed when exit

   // button is clicked

   private class ExitButtonListener implements ActionListener {

   @Override

   public void actionPerformed(ActionEvent e) {

   //simply exiting

   System.exit(0);

   }

   }
  
}

//end of KiloConverter.java

// /////////////////////// Driver.java /////////////////////////////////

//public driver program to run the KiloConverter class

public class Driver {

public static void main(String[] args) {

KiloConverter converter = new KiloConverter();

converter.setVisible(true);

}

}

//end of Driver.java