How to add action listener that listens to multiple buttons
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)
}
}
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");
}
}
}