How can I set a JPanel maximum or preferred size that uses gridLayout?

Question

Hi guys, I had problem using a very simple frame containing two JPanel. The problem is on the layout of the Center JPanel that contains four JButton. How can I set a better size for buttons or directly for JPanel that uses the GridLayout. On the picture the problem:

!

Here the code: ` JFrame window = new JFrame("Horrible! LOL");

    JTextField textField = new JTextField("");
    textField.setPreferredSize(new Dimension(200,20));
    JPanel textPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
    textPanel.add(textField);
    window.add(textPanel, BorderLayout.NORTH);

    JButton plus = new JButton("+");
    //plus.setPreferredSize(new Dimension(50,50)); nothing would change
    JButton minus = new JButton("-");
    JButton per = new JButton("x");
    JButton divide = new JButton("/");
    JPanel prova = new JPanel(new GridLayout(2,2,10,10));
    Dimension d = new Dimension(20,20);
    prova.setMaximumSize(d); // nothing changed!

    prova.add(plus);
    prova.add(minus);
    prova.add(per);
    prova.add(divide);
    window.add(prova, BorderLayout.CENTER);

    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    window.setSize(250,300);
    window.setResizable(false);
    window.setVisible(true);`

Which is a good solution?

Kind regards

Answer 1

Unfortunately gridlayout doesent respect preferred sizes. But still if you want to stick to grid layout then you can try something like this:

    public static JComponent wrap(JComponent comp)
    {
        JPanel panel = new JPanel();
        panel.add(comp);
        return panel;
    }

And then instead of direclty adding in to prova add like this:

            prova.add(wrap(plus)); 
            prova.add(wrap(minus)); 
            prova.add(wrap(per)); 
            prova.add(wrap(divide));

Tested, Works perfect!! There are other better ways though

Answer 2

That's what happen to me: It's definitely attached to the upper edge of the grid.

Even if in this case, in the wrap method I can set the preferredSize of buttons/comp, every buttons is on its own edge. What about others solutions. How would you position buttons for a calculator? Kind regards and thanx angain!