Cannot make GridBagLayout contents descend from the top

Question

I have a JFrame with five buttons added to the contents panel. I intended for the X axis to begin at the very top of the frame, however, when the frame is resized the contents are shifted towards the middle. How do I maintain all of the components floating to the top.

How it looks

Here is my code (shortened)

 
public class GridBagLayoutDemo {
    final static boolean shouldFill = true;
    final static boolean shouldWeightX = true;
    final static boolean RIGHT_TO_LEFT = false;
 
    public static void addComponentsToPane(Container pane) {
        if (RIGHT_TO_LEFT) {
            pane.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
        }
 
        JButton button;
    pane.setLayout(new GridBagLayout());
    GridBagConstraints c = new GridBagConstraints();
    if (shouldFill) {
    //natural height, maximum width
    c.fill = GridBagConstraints.HORIZONTAL;
    }
 
    button = new JButton("Button 1");
    if (shouldWeightX) {
    c.weightx = 0.5;
    }
    c.fill = GridBagConstraints.HORIZONTAL;
    c.gridx = 0;
    c.gridy = 0;
    pane.add(button, c);
 
    button = new JButton("Button 2");
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 0.5;
    c.gridx = 1;
    c.gridy = 0;
    pane.add(button, c);
 
    button = new JButton("Button 3");
    c.fill = GridBagConstraints.HORIZONTAL;
    c.weightx = 0.5;
    c.gridx = 2;
    c.gridy = 0;
    pane.add(button, c);
 
    button = new JButton("Long-Named Button 4");
    c.fill = GridBagConstraints.HORIZONTAL;
    //c.ipady = 40;      //make this component tall
    c.weightx = 0.0;
    c.gridwidth = 3;
    c.gridx = 0;
    c.gridy = 1;
    pane.add(button, c);
 
    button = new JButton("5");
    c.fill = GridBagConstraints.HORIZONTAL;
    //c.ipady = 40;      //make this component tall
    c.weightx = 0.0;
    c.gridwidth = 3;
    c.gridx = 0;
    c.gridy = 2;
    pane.add(button, c);
    }

    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("GridBagLayoutDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
        //Set up the content pane.
        addComponentsToPane(frame.getContentPane());
      
        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }
 
    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

Answer 1

GridBagLayout will, by default, layout components around the middle of the container.

You can, however, modify the amount of remaining space a component will occupy through the use of weightx and weighty, for example, if you added...

// It's transparent by default...
JComponent filler = new JComponent() {};
c.gridy++;
c.weighty = 1;
pane.add(filler, c);

Probably after...

button = new JButton("5");
c.fill = GridBagConstraints.HORIZONTAL;
//c.ipady = 40;      //make this component tall
c.weightx = 0.0;
c.gridwidth = 3;
c.gridx = 0;
c.gridy = 2;
pane.add(button, c);

You'd get...

Now, personally, I'd consider using compound layouts, as finding the "last" y position might not always be feasible

See How to Use GridBagLayout for more details