user519670 user519670 - 7 months ago 14
Java Question

How to add action listener that listens to multiple buttons

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

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)
    }  

}