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 use an action listener.

Below is a simple program that im trying to get a button working in.

What am i doing wrong?

import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JButton; import javax.swing.JFrame;   public class calc extends JFrame implements ActionListener {        public static void main(String[] args) {          JFrame calcFrame = new JFrame();          calcFrame.setSize(100, 100);         calcFrame.setVisible(true);          JButton button1 = new JButton("1");         button1.addActionListener(this);          calcFrame.add(button1);     }      public void actionPerformed(ActionEvent e) {         if(e.getSource() == button1)     }    } 

the action listener is never registered because with the if(e.getSource() == button1) it cant see button1, errors saying cannot find symbol.

Answer 1

There is no this pointer in a static method. (I don't believe this code will even compile.)

You shouldn't be doing these things in a static method like main(); set things up in a constructor. I didn't compile or run this to see if it actually works, but give it a try.

public class Calc extends JFrame implements ActionListener {      private Button button1;      public Calc()     {         super();         this.setSize(100, 100);         this.setVisible(true);          this.button1 = new JButton("1");         this.button1.addActionListener(this);         this.add(button1);     }       public static void main(String[] args) {          Calc calc = new Calc();         calc.setVisible(true);     }      public void actionPerformed(ActionEvent e) {         if(e.getSource() == button1)     }    } 

Answer 2

I'm amazed that nobody has mentioned using an action command. This is a pretty standard way of associating sources and listeners. Its really useful if;

• you have multiple event sources that need to do the same thing (eg if you want the use to be able to press the enter key on a text field as an alternative to clicking a button next to it)
• you don't have a ref to the component generating the event

see;

import java.awt.FlowLayout; import java.awt.event.ActionEvent;     import java.awt.event.ActionListener; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JOptionPane;  public class DontExtendJFrame implements ActionListener {    private enum Actions {     HELLO,     GOODBYE   }    public static void main(String[] args) {      DontExtendJFrame instance = new DontExtendJFrame();      JFrame frame = new JFrame("Test");     frame.setLayout(new FlowLayout());     frame.setSize(200, 100);      JButton hello = new JButton("Hello");     hello.setActionCommand(Actions.HELLO.name());     hello.addActionListener(instance);     frame.add(hello);      JButton goodbye = new JButton("Goodbye");     goodbye.setActionCommand(Actions.GOODBYE.name());     goodbye.addActionListener(instance);     frame.add(goodbye);      frame.setVisible(true);   }    @Override   public void actionPerformed(ActionEvent evt) {     if (evt.getActionCommand() == Actions.HELLO.name()) {       JOptionPane.showMessageDialog(null, "Hello");     } else if (evt.getActionCommand() == Actions.GOODBYE.name()) {       JOptionPane.showMessageDialog(null, "Goodbye");     }   } }