Trying to do a basic calculator...

[TheChodja]

I really didn't want to have to resort to this, but I don't have a lot of resources, and what little I do have aren't really teaching me anything. It's an assignment for school. I'm not asking anyone to fill out the code for me, I just really need to understand how to go about doing something like this. I wager it's really easy, but I've been trying to wrap my head around it for more than a week now and it's already quite a bit overdue (it was due this past Monday).

I'm very new to Java, and I'm learning it in the worst way: online classes.

If you don't want to help me on the basis that it's a school assignment, that's cool, just ignore me.
Otherwise, I really need help.
I'm pretty sure I'm stuck on ActionListeners and ActionEvents.
I've tried various things to get it to work, but everything I've tried has rendered unsuccessful builds.

I don't need number buttons, just the sign buttons and then, I guess, the equal button has to follow up and do all the math work...

I guess just give me some pointers on the whole actionlistener event thingies.
Or maybe point me to a really simplified tutorial on how to get this thing, or things like it, to work...

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class BasicCalculator {
	private static final int FRAME_WIDTH = 150;
	private static final int FRAME_HEIGHT = 120;

	// Keeps track of the current operation (subtract, add, etc)
	private static final int NO_OPERATION = 0;
	private static final int ADDITION = 1;
	public static int operation = NO_OPERATION;

	public static JTextField textFieldDisplay;
	public static double Value1 = 0; // holds the value before the operation

	public static void main(String[] args) {
		// Set up the user interface
		JFrame frame = new JFrame();
		JPanel buttonPanel = new JPanel();
		frame.add(buttonPanel);

		// create two buttons, plus and equal and a text box for answers
		textFieldDisplay = new JTextField(10);
		buttonPanel.add(textFieldDisplay);
		JButton buttonPlus = new JButton(" + ");
		buttonPanel.add(buttonPlus);
                JButton buttonMinus = new JButton(" - ");
		buttonPanel.add(buttonMinus);
                JButton buttonMulti = new JButton(" x ");
		buttonPanel.add(buttonMulti);
                JButton buttonDivi = new JButton(" / ");
		buttonPanel.add(buttonDivi);
		JButton buttonEqual = new JButton(" = ");
		buttonPanel.add(buttonEqual);

		frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
		frame.setTitle("Basic Calculator");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setVisible(true);


		// called when the equal sign '=' is pressed
		class EqualSignListener implements ActionListener {

			public void actionPerformed(ActionEvent event)
			{
				double Value2 = Double.parseDouble(textFieldDisplay.getText());
				if (operation == ADDITION) {
					// plus sign pressed before the equal sign
					Value2 += Value1;
				}
				// Convert from a answer to a string
				Double answer = new Double(Value2);
				textFieldDisplay.setText( answer.toString() );
				// Reset the operation to show no current operation
				operation = NO_OPERATION;
			}
		}

		// called when a plus sign '+' is pressed
		class PlusSignListener implements ActionListener {
			public void actionPerformed(ActionEvent event)
			{
				Value1 = Double.parseDouble(textFieldDisplay.getText());
				operation = ADDITION;
			}
		}

		// Add the methods that will be called when these buttons are pressed
		ActionListener plusSignListener = new PlusSignListener();
		buttonPlus.addActionListener(plusSignListener);

		ActionListener equalSignListener = new EqualSignListener();
		buttonEqual.addActionListener(equalSignListener);

	}
}

[Reskaillev]

Oracle has the best tutorials XD

here you go: How to Write an Action Listener (The Java™ Tutorials > Creating a GUI With JFC/Swing > Writing Event Listeners)

And maybe you should start with something easier? How about a frame with 1 button that prints something in the command line if you press it? That way you would understand the concept without getting lost in a spaghetti of code. :p

Im my opinion the Oracle java tutorials are the best you will find on the web!