Java GridBagLayout : make component align to left

Question

I have this layout using GridBagLayout:

public class Example extends JFrame {
    public Example() {
        Border outline = BorderFactory.createLineBorder(Color.black);
        GridBagLayout gbl = new GridBagLayout();
        GridBagConstraints gbc = new GridBagConstraints();
        JPanel pane = new JPanel(gbl);

        gbc.weighty = 1.0;
        gbc.weightx = 1.0;

        JLabel unitLbl = new JLabel("Unit");
        unitLbl.setBorder(outline);
        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.ipadx = 30;
        gbc.ipady = 10;
        gbl.setConstraints(unitLbl, gbc);
        pane.add(unitLbl);

        JLabel typeLbl = new JLabel("Type");
        typeLbl.setBorder(outline);
        gbc.gridx = 0;
        gbc.gridy = 1;
        gbc.ipadx = 30;
        gbc.ipady = 10;
        gbl.setConstraints(typeLbl, gbc);
        pane.add(typeLbl);

        JTextField unitField = new JTextField();
        typeLbl.setBorder(outline);
        gbc.gridx = 1;
        gbc.gridy = 0;
        gbc.ipadx = 30;
        gbc.ipady = 10;
        gbl.setConstraints(unitField, gbc);
        pane.add(unitField);

        String[] type = {"All", "Verb", "Noun", "Adjective"};
        JComboBox<String> comboBox = new JComboBox<String>(type);
        gbc.gridx = 1;
        gbc.gridy = 1;
        gbc.ipadx = 30;
        gbc.ipady = 10;
        gbl.setConstraints(comboBox, gbc);
        pane.add(comboBox);


        add(pane, BorderLayout.CENTER);
        setSize(new Dimension(400, 300));
        getContentPane().setBackground(Color.WHITE);
        setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Example();
            }
        });
    }
}

In this example, when run, It seems that every component is at the center of the frame. But what I want is :

1. Two JLabel (unitLbl and typelbl) will be on the left of frame
2. JTextField and JComboBox will be on the right of two JLabel, respectively with a small distance between.
3. Moreover, I want to add a new JButton at location (3,0) of the grid, but the height of this location sum of two JLabel height. It means, this button height is on "two line".

How can I fix this code to achieve this goal ? Please help me.

Thanks :)

Answer 1

You want to use GridBagConsraints#anchor to define the position within the cell that you want to align the component to.

To allow a component to span over number of cells, you want to use GridBagConstraints#gridwidth and GridBagConstraints#gridheight (the default is 1)

public class TestLayout09 {

    public static void main(String[] args) {
        new TestLayout09();
    }

    public TestLayout09() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException ex) {
                } catch (InstantiationException ex) {
                } catch (IllegalAccessException ex) {
                } catch (UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new LayoutPane());
                frame.setBackground(Color.WHITE);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }

        });
    }

    public class LayoutPane extends JPanel {

        public LayoutPane() {
            Border outline = BorderFactory.createLineBorder(Color.black);
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();

            // I'm not sure this really is what you want, but I may be mistaken
//            gbc.weighty = 1.0;
//            gbc.weightx = 1.0;

            JLabel unitLbl = new JLabel("Unit");
            unitLbl.setBorder(outline);
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.ipadx = 30;
            gbc.ipady = 10;
            gbc.anchor = GridBagConstraints.WEST;
            add(unitLbl, gbc);

            JLabel typeLbl = new JLabel("Type");
            typeLbl.setBorder(outline);
            gbc.gridx = 0;
            gbc.gridy = 1;
            gbc.ipadx = 30;
            gbc.ipady = 10;
            add(typeLbl, gbc);

            JTextField unitField = new JTextField();
            typeLbl.setBorder(outline);
            gbc.gridx = 1;
            gbc.gridy = 0;
            gbc.ipadx = 30;
            gbc.ipady = 10;
            gbc.anchor = GridBagConstraints.EAST;
            add(unitField, gbc);

            String[] type = {"All", "Verb", "Noun", "Adjective"};
            JComboBox<String> comboBox = new JComboBox<String>(type);
            gbc.gridx = 1;
            gbc.gridy = 1;
            gbc.ipadx = 30;
            gbc.ipady = 10;
            add(comboBox, gbc);

            JButton btn = new JButton("Test");
            gbc.gridx = 3;
            gbc.gridy = 0;
            gbc.fill = GridBagConstraints.BOTH;
            gbc.gridheight = 2;
            add(btn, gbc);
        }
    }
}