CODEWITHSUNDEEP
javaswinggridbaglayout
WilliamShatner
WilliamShatner

Reputation: 926

How to add components dynamically divided evenly between two columns?

I currently have an array of JButtons and I want to place them on my JPanel in two columns, split evenly. So if there are 8 buttons in the array there would be 4 buttons in the left column and 4 buttons in the right column. However, if there are 7 buttons in the array, the left column would have 4 buttons and the right column would have 3 buttons.

I went about and create some basic logic for such a scenario and wanted to see if there was any logic error in the code I made (or perhaps a better way of doing this).

Here is the code I've come up with

public class SwingTest {

    public static void main(String[] args) {
        JFrame frame = new JFrame();

        JButton b1 = new JButton();
        b1.setText("Button1");

        JButton b2 = new JButton();
        b2.setText("Button2");

        JButton b3 = new JButton();
        b3.setText("Button3");

        JButton b4 = new JButton();
        b4.setText("Button4");

        JButton b5 = new JButton();
        b5.setText("Button5");

        JButton b6 = new JButton();
        b6.setText("Button6");

        ArrayList<JButton> jButtonList = new ArrayList();
        jButtonList.add(b1);
        jButtonList.add(b2);
        jButtonList.add(b3);
        jButtonList.add(b4);
        jButtonList.add(b5);
        jButtonList.add(b6);

        JPanel panel = new JPanel();
        panel.setLayout(new java.awt.GridBagLayout());

        double halfList = Math.ceil((jButtonList.size() / 2.0));
        int gridX = 0, gridY = 0;

        for(int i = 0; i < jButtonList.size(); i++) {
            GridBagConstraints gridBagConstraints = new java.awt.GridBagConstraints();

            if(gridY == (int)halfList) {
                gridX++;
                gridY = 0;
            }
            gridBagConstraints.gridx = gridX;
            gridBagConstraints.gridy = gridY;
            gridBagConstraints.fill = java.awt.GridBagConstraints.BOTH;
            gridBagConstraints.weightx = 1.0;
            gridBagConstraints.weighty = 1.0;
            gridBagConstraints.insets = new java.awt.Insets(1, 0, 1, 0);
            panel.add(jButtonList.get(i), gridBagConstraints);
            gridY++;
        }
        frame.add(panel);
        frame.pack();
        frame.setVisible(true);
    }
}

The sample code seems to work fine, but will there ever be a case where it might hiccup?

Upvotes: 1

Views: 2219

Answers (2)

Dan D.
Dan D.

Reputation: 32391

Using a GridBagLayout for this seems to be a good plan.

However, I would clean up the button building code a little bit. What happens if you will need 100 buttons? Manually adding 100 buttons doesn't seem to be a good idea. I would have a parametrized method for building and returning a button and a loop for adding the buttons to your ArrayList.

Upvotes: 1

Roger
Roger

Reputation: 348

You may use a JPanel with GridLayout passing 0 lines in its constructor with 2 columns:

JPanel panel = new JPanel(new GridLayout(0 ,2));

It means that the panel will increase in height when you add components to it, while keeping always 2 columns

The code to add the JButtons will be as simple as this:

for(int i = 0; i < jButtonList.size(); i++) {
    panel.add(jButtonList.get(i));
}

Upvotes: 4

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