[java] How to set the component size with GridLayout? Is there a better way?

I am working on a larger GUI with Java and I am becoming angry on Layout Managers.

I have a "Settings-Panel" with a variable number of JComponents in it (Labels, Buttons, JSpinners, JSliders,...). I just want the following:

JLabel <-> JComponent

JLabel <-> JComponent

JLabel <-> JComponent

...

My Panel has a size of 500px, so that there is enough space for a lot of components. Unfortunatly the GridLayout always stretches the size of the Components to the whole Panel, even if I set a MaximumSize for every component. It looks stupid if there are only two buttons each with a height of 250px.

I tried flow Layout, but i cannot figure out a way to make new lines properly. I tried BoxLayout.Y_AXIS, but the Components are always centered, and Label and Component are not in the same line.

Does anybody know a good and short way with LayoutManagers to handle this properly?

In my project I managed to use GridLayout and results are very stable, with no flickering and with a perfectly working vertical scrollbar.

First I created a JPanel for the settings; in my case it is a grid with a row for each parameter and two columns: left column is for labels and right column is for components. I believe your case is similar.

JPanel yourSettingsPanel = new JPanel();
yourSettingsPanel.setLayout(new GridLayout(numberOfParams, 2));

I then populate this panel by iterating on my parameters and alternating between adding a JLabel and adding a component.

for (int i = 0; i < numberOfParams; ++i) {
    yourSettingsPanel.add(labels[i]);
    yourSettingsPanel.add(components[i]);
}

To prevent yourSettingsPanel from extending to the entire container I first wrap it in the north region of a dummy panel, that I called northOnlyPanel.

JPanel northOnlyPanel = new JPanel();
northOnlyPanel.setLayout(new BorderLayout());
northOnlyPanel.add(yourSettingsPanel, BorderLayout.NORTH);

Finally I wrap the northOnlyPanel in a JScrollPane, which should behave nicely pretty much anywhere.

JScrollPane scroll = new JScrollPane(northOnlyPanel,
                                     JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                                     JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);

Most likely you want to display this JScrollPane extended inside a JFrame; you can add it to a BorderLayout JFrame, in the CENTER region:

window.add(scroll, BorderLayout.CENTER);

In my case I put it on the left column of a GridLayout(1, 2) panel, and I use the right column to display contextual help for each parameter.

JTextArea help = new JTextArea();
help.setLineWrap(true);
help.setWrapStyleWord(true);
help.setEditable(false);

JPanel split = new JPanel();
split.setLayout(new GridLayout(1, 2));
split.add(scroll);
split.add(help);

An alternative to other layouts, might be to put your panel with the GridLayout, inside another panel that is a FlowLayout. That way your spacing will be intact but will not expand across the entire available space.

Don't use GridLayout for something it wasn't meant to do. It sounds to me like GridBagLayout would be a better fit for you, either that or MigLayout (though you'll have to download that first since it's not part of standard Java). Either that or combine layout managers such as BoxLayout for the lines and GridLayout to hold all the rows.

For example, using GridBagLayout:

import java.awt.*;
import javax.swing.*;

public class LayoutEg1 extends JPanel{
    private static final int ROWS = 10;

    public LayoutEg1() {
        setLayout(new GridBagLayout());
        for (int i = 0; i < ROWS; i++) {
            GridBagConstraints gbc = makeGbc(0, i);
            JLabel label = new JLabel("Row Label " + (i + 1));
            add(label, gbc);

            JPanel panel = new JPanel();
            panel.add(new JCheckBox("check box"));
            panel.add(new JTextField(10));
            panel.add(new JButton("Button"));
            panel.setBorder(BorderFactory.createEtchedBorder());
            gbc = makeGbc(1, i);
            add(panel, gbc);
        }
    }

    private GridBagConstraints makeGbc(int x, int y) {
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridwidth = 1;
        gbc.gridheight = 1;
        gbc.gridx = x;
        gbc.gridy = y;
        gbc.weightx = x;
        gbc.weighty = 1.0;
        gbc.insets = new Insets(5, 5, 5, 5);
        gbc.anchor = (x == 0) ? GridBagConstraints.LINE_START : GridBagConstraints.LINE_END;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        return gbc;
    }

    private static void createAndShowUI() {
        JFrame frame = new JFrame("Layout Eg1");
        frame.getContentPane().add(new LayoutEg1());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                createAndShowUI();
            }
        });
    }
}

For more complex layouts I often used GridBagLayout, which is more complex, but that's the price. Today, I would probably check out MiGLayout.

You need to try one of the following:

1. GridBagLayout
2. MigLayout
3. SpringLayout

They offer many more features and will be easier to get what you are looking for.