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javaswinggridbaglayout

GridBagLayout controls alignment in Swing

I have this window that has a JScrollPane almost all over it. I'm adding large buttons (that have images attached to them) to it and I expect them to keep adding downwards, thats why I'm using a GridBagLayout and I set gbc.gridx, gbc.gridy everytime I add a button.

The scrolling thing works fine: enter image description here

but the problem is, when I add less than 4 buttons, they align to the center of the row, instead to the left side as I want them to. Like this

enter image description here

Any idea how can I align them to the left? I tried gbc.anchor and gbc.fill but no luck. Thanks

Here's the panel inside my JScrollPane

private JPanel imagesPanel() {
        JPanel panel = new JPanel(new GridBagLayout());

        int x = 0;
        int y = 0;

        GridBagConstraints c = new GridBagConstraints();
        //c.anchor = GridBagConstraints.NORTHWEST;

        //add all images as buttons
        List<PuzzleImage> imageList = _imageLoader.getImageCollection().getAllImages();
        for(PuzzleImage puzzleImage : imageList) {
            for(int i = 0; i < 1; i++) { //ignore this, just for debugging. i add 3 images
                ImageIcon imageIcon = new ImageIcon(puzzleImage.getLowScaleImage());

                c.gridx = x;
                c.gridy = y;
                c.weightx = 1.0;

                JButton btn = new JButton(imageIcon);
                btn.setPreferredSize(new Dimension(ImageLoader.LOW_SCALE_IMAGE_SIZE, ImageLoader.LOW_SCALE_IMAGE_SIZE));
                panel.add(btn, c);

                x++;
                if(x>=4) {
                    x = 0;
                    y++;
                }
            }
        }

        return panel;
    }
Solution

  • but the problem is, when I add less than 4 buttons, they align to the center of the row, instead to the left side as I want them to

    At least one of the components need to have a weightx constraint greater than 0.

    Read the section from the Swing tutorial on How to Use GridBagLayout. The section that explains how the constraints works will provide more information.

    Why are you even using a GridBagLayout? You were given a simple solution I your last question: FlowLayout in Swing doesn't move to the next line. Then you don't even need to worry about constraints.

    Or you could use a GridLayout You simply define that you want 4 columns and components automatically wrap. You may need to nest panels so components don't shrink/grow depending on the size of the frame.

    Basic code is:

    JPanel wrapper = new JPanel();
JPanel buttons = new JPanel( new GridLayout(0, 4) );

for (...)
{
    JButton button = new JButton(...);
    buttons.add( button );
}

frame.add(wrapper);