GUI Error and Button Question

[Kid Programmer]

Hello guys. I am trying to create a calculator program in a GUI window. When I compile the code I get the following errors:
Severity and Description Path Resource Location Creation Time Id
The local variable add is never read CalculatorProgr am/src/Calculator Calculator.java line 19 1211809496146 548
The local variable contentPane is never read CalculatorProgr am/src/Calculator Calculator.java line 17 1211809496146 545
The local variable divide is never read CalculatorProgr am/src/Calculator Calculator.java line 19 1211809496146 551
The local variable layout is never read CalculatorProgr am/src/Calculator Calculator.java line 20 1211809496146 552
The local variable multiply is never read CalculatorProgr am/src/Calculator Calculator.java line 19 1211809496146 550
The local variable num1 is never read CalculatorProgr am/src/Calculator Calculator.java line 18 1211809496146 546
The local variable num2 is never read CalculatorProgr am/src/Calculator Calculator.java line 18 1211809496146 547
The local variable subtract is never read CalculatorProgr am/src/Calculator Calculator.java line 19 1211809496146 549

Here is my code:

package Calculator;

//import declarations
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JButton;
import javax.swing.JTextField;
import java.awt.Container;
import java.awt.FlowLayout;

//create a new class
public class Calculator {
	
	//create the main function
	public static void main(String[] args) {
		//variable declaration
		JFrame frame;
		Container contentPane;
		JTextField num1, num2;
		JButton add, subtract, multiply, divide;
		JLabel result;
		FlowLayout layout;
		
		frame = new JFrame();
		frame.setTitle("Calculator");
		
		contentPane = frame.getContentPane();
		
		num1 = new JTextField("Number 1");
		num2 = new JTextField("Number 2");
		
		add = new JButton("Add");
		subtract = new JButton("Subtract");
		multiply = new JButton("Multiply");
		divide = new JButton("Divide");
		
		result = new JLabel("Result");
		
	}

}

The code is not yet finished. My second question is how do you cause an event to happen when a button is clicked. When the for example add button is clicked I want to do this:

		int number1, number2, sum;
		number1 = (int)((Double.parseDouble(num1.getText())));
        number2 = (int)((Double.parseDouble(num2.getText())));
        sum = number1 + number2;
        result.setText("" + sum);

[Laharl]

You'd use an ActionListener for the button event. As to the others...beats me.

[Kid Programmer]

You'd use an ActionListener for the button event. As to the others...beats me.

I knew I needed to use an actionlistener but I don't know how.

[BigDaddyLH]

What compiler are you using? Those are odd messages. I think the latter ones are because your code is incomplete -- you create those widgets but do nothing with them.

[Kid Programmer]

What compiler are you using? Those are odd messages. I think the latter ones are because your code is incomplete -- you create those widgets but do nothing with them.

I am not sure what compiler I am using. The mac I use had a java compiler built in. I have a mac version 10.5.2. I could download a new compiler though...

[Laharl]

That'd be Apple's compiler then...as for the ActionListener, Google 'actionlistener tutorial' or something similar.

[Kid Programmer]

That'd be Apple's compiler then...as for the ActionListener, Google 'actionlistener tutorial' or something similar.

I already did and found this:
https://cis.med.ucalgar y.ca/http/java.sun.com/docs/books/tutorial/uiswing/events/actionlistener. html

But I didn't understand 100% of it. Mainly I just didn't get what this code was for

add(b);
add(text);

[BigDaddyLH]

You're looking at an old pre-Swing tutorial, there. I suggest you bookmark this page to the real thing:

http://java.sun.com/docs/books/tutorial/index.html

[Kid Programmer]

Well guys I fixed up my code and I think I will just make a new thread actually all about ActionListeners . So here is my new code:

/**
 * Written By: Edward Sanger
 * Coded in: Java
 * IDE Used: IntelliJ IDEA
 * Program Name: Calculator
 * Program Description: This program will create a GUI window with 4 buttons for 4 mathematical operators and 2 text
 * fields for the numbers to add, subtract, multiply, and divide.
 * Date: May 26, 2008
 * Time: 2:34:52 PM
 */

//import declarations
import java.awt.*;
import javax.swing.*;

public class Calculator implements ActionListener {
    public static void main(String[] args) {
        //create a new jframe
        JFrame frame = new JFrame();
        frame.setTitle("Calculator");
        //create a container
        Container contentPane = frame.getContentPane();

        //create the frame objects
        JTextField num1 = new JTextField("Number 1");
        JTextField num2 = new JTextField("Number 2");

        JButton add = new JButton("Add");
        JButton subtract = new JButton("Subtract");
        JButton multiply = new JButton("Multiply");
        JButton divide = new JButton("Subtract");

        JLabel result = new JLabel("Result");

        //add the objects
        contentPane.add(num1);
        contentPane.add(num2);
        
        contentPane.add(add);
        contentPane.add(subtract);
        contentPane.add(multiply);
        contentPane.add(divide);

        contentPane.add(result);

        //create the layout
        FlowLayout layout = new FlowLayout();
        contentPane.setLayout(layout);

        //create an action listener
        

        //frame settings
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }
}