ActionListeners and JButtons

Question

I'm trying write a program where I have 3 different buttons and when you click a button it changes the background of a panel in the frame. I got my panel set up and everything is in the right place, but I need to have all my actionlisteners for my buttons all in one class. I tried doing that but all the buttons change colors and not the background. Here's the code I have so far.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

/*
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 * and open the template in the editor.
 */

/**
 *
 * @author Kelle Schmitt
 */
public class BackgroundColorChooserFrame extends JFrame
{
    private static final int WIDTH = 300;
    private static final int HEIGHT = 300;

    private JLabel titleLbl;
    private JButton redBtn;
    private JButton greenBtn;
    private JButton blueBtn;
    private JButton quitBtn;

    public BackgroundColorChooserFrame()
    {
        createButton();
        createLabel();
        createPanel();

        setSize(WIDTH, HEIGHT);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    class ColorListener implements ActionListener
    {
        public void actionPerformed(ActionEvent evt)
        {
            redBtn.setBackground(Color.red);
            greenBtn.setBackground(Color.green);
            blueBtn.setBackground(Color.blue);
        }
    }

    public void createButton()
    {
        redBtn = new JButton("Red");
        greenBtn = new JButton("Green");
        blueBtn = new JButton("Blue");

        ActionListener colorlistener = new ColorListener();
        redBtn.addActionListener(colorlistener);
        greenBtn.addActionListener(colorlistener);
        blueBtn.addActionListener(colorlistener);
    }

    public void createLabel()
    {
        titleLbl = new JLabel("Background Color Chooser");
    }

    //create and add panels
    public void createPanel()
    {
        JPanel mainPnl, titlePnl, colorPnl, controlPnl;

        mainPnl = new JPanel();
        mainPnl.setLayout(new BorderLayout());
        titlePnl = new JPanel();
        colorPnl = new JPanel();
        controlPnl = new JPanel();

        mainPnl.add(titlePnl, BorderLayout.NORTH);
        titlePnl.add(titleLbl);
        mainPnl.add(colorPnl, BorderLayout.CENTER);
        mainPnl.add(controlPnl, BorderLayout.SOUTH);
        controlPnl.add(redBtn);
        controlPnl.add(greenBtn);
        controlPnl.add(blueBtn);

        //add the mainPnl to the parent frame
        add(mainPnl);

    }


}

Please help! Thanks!

Answer 1

Maybe something like:

public void actionPerformed(ActionEvent evt)
{
    JButton button = (JButton)evt.getSource();
    Component parent = button.getParent();

    if (button == redBtn)
        parent.setBackground( Color.RED );
    else if (...)
}

Although a much better solution is to create a separate ActionListener for every button so you don't use nested if/else logic:

public class ColorListener implements ActionListener
{
    private Color background;

    public ButtonListener(Color background)
    {
        this.background = background;
    }

    @Override
    public void actionPerformed(ActionEvent e)
    {
        JButton button = (JButton)evt.getSource();
        Component parent = button.getParent();
        parent.setBackground( background );   
    }
}

Then you can create an unlimited number of buttons and colors:

redButton.addActionListener( new ColorListener(Color.RED) );

The key point is in using the getSource() method so you can write generic code.