Creating an Array of JButton

Question

Basically I am trying to make a Lightout game! I want to make an array of JButtons so I can keep track of the index of each of them (the reason being the state of each button is dependant on the state of the others)

so far I have:

JPanel panel = new JPanel();
    setTitle("Memory");
    setContentPane(panel);
    setPreferredSize(new Dimension(300, 300));
    panel.setLayout(new GridLayout(5,5));


    JButton[][] buttons = new JButton[5][5] ;
    for (int i = 0; i < 5; i++)
        for (int j = 0; j < 5; j++) {
          buttons[i][j] = new JButton();

    setDefaultCloseOperation(EXIT_ON_CLOSE);
    pack();
    setVisible(true);
        }

But this isnt working how I expect it to. I just got a big blank JFrame when I run this. Any help would be appreciated

I was under the impression that buttons[i][j] = new JButton(); was the way to add buttons? Im really sorry, I'm kinda a noob at this — Elchapo
– Elchapo, Commented Apr 7, 2016 at 4:02
@Elchapo your for loop is bad .how much time you call pack and setvisible — Madhawa Priyashantha
– Madhawa Priyashantha, Commented Apr 7, 2016 at 4:06
@Elchapo that's why it's discourage to omit curly brackets in for loop. there is a higher change to make a mistake .so use curly brackets to wrap if blocks — Madhawa Priyashantha
– Madhawa Priyashantha, Commented Apr 7, 2016 at 4:17

Sajeev · Accepted Answer · 2016-04-07 04:57:16Z

5

The attached code should fix it. You were creating button, but not adding it to the JFrame. I have edited the code to add action listener which accesses the id of the JButton and displays it , when you click it.

public class CodeSample extends JFrame {

private static final long serialVersionUID = -8134989438964195251L;

public CodeSample() {
    JPanel panel = new JPanel();
    setTitle("Memory");
    setContentPane(panel);
    setPreferredSize(new Dimension(300, 300));
    panel.setLayout(new GridLayout(5, 5));
    ButtonListener listener = new ButtonListener();

    JButton[][] buttons = new JButton[5][5];
    for (int i = 0; i < 5; i++) {
        for (int j = 0; j < 5; j++) {
            buttons[i][j] = new JButton();
            buttons[i][j].setBackground(Color.black);
            buttons[i][j].putClientProperty("id",
                    String.valueOf(i).concat(String.valueOf(j)));
            buttons[i][j].addActionListener(listener);
            panel.add(buttons[i][j]);
        }
    }

    setDefaultCloseOperation(EXIT_ON_CLOSE);
    pack();
    setVisible(true);
}

public static class ButtonListener implements ActionListener {

    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println(((JButton) e.getSource())
                .getClientProperty("id"));
    }

}

public static void main(String[] args) {
    new CodeSample();
}
}

edited Apr 7, 2016 at 4:57

answered Apr 7, 2016 at 4:02

Sajeev

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8 Comments

Elchapo Over a year ago

Thanks a ton! that makes sense now! just to be clear, this definitely had to be a Matrix array correct? and the button at index [0][0] is going to be top left button?

Sajeev Over a year ago

@Elchapo yes that`s right [0][0] is going to be top left button. The can be implemented in multiple ways. Matrix array is a good choice for this case.

user4509668 Over a year ago

This implementation is a matrix, but JButton (like any object) need not necessarily be stored in a two-dimensional array. One could also have a one-dimensional array of buttons.

Elchapo Over a year ago

@ingrid Thanks a bunch! I can set the background on the buttons with buttons[i][j].setBackground(color.black); correct? (Im on a mac if that makes a difference..)

Sajeev Over a year ago

@Elchapo spot on. You can add back ground by calling buttons[i][j].setBackground(color.black);

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