How to add action listener that listens to multiple buttons

Question

I\'m trying to figure out what i am doing wrong with action listeners. I\'m following multiple tutorials and yet netbeans and eclipse are giving me errors when im trying to

Answer 1

You've been told how to sort your immediate problem, but I think there are more important problems here.

• stick with conventions. Even for throw-away code. That means initial cases for class names.

• Don't extend classes you don't need to. JFrame should rarely be extended. In fact, you don't create an instance of your derived class!!!

• Don't bundle a bunch of things into one class. In particular, you should generally only subtype at most one main class or interface at a time (things like Comparable not included).

• Always interact, including construct, Swing/AWT GUIs on the AWT Event Dispatch Thread (EDT). It's ugly and verbose, but that's Java for you.

• Checking a source of an event is a bit of hack. Listeners are small, so you can't even claim the lame performance excuse.

So:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;


public class Calc {
    public static void main(String[] args) {
        java.awt.EventQueue.invokeLater(new Runnable() { public void run() {
            runEDT();
        }});
    }
    private static void runEDT() {
        assert java.awt.EventQueue.isDispatchThread();

        JFrame frame = new JFrame();

        frame.setSize(100, 100);

        JButton button1 = new JButton("1");
        button1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                ...
            }
        });

        frame.add(button1);

        frame.setVisible(true);
    }
}

If you need to access any of the variables from the enclosing method within the listener, make them final.