How to align left or right inside GridBagLayout cell?

Question

I see that GridBagLayout positions it's children with center alignment within cells. How to align left or right?

UPDATE

Constructing code (I know I could reuse c)

    // button panel
    JPanel button_panel = new JPanel();
    button_panel.add(ok_button);
    button_panel.add(cancel_button);

    // placing controls to dialog
    GridBagConstraints c;

    GridBagLayout layout = new GridBagLayout();
    setLayout(layout);

    c = new GridBagConstraints();
    c.gridx = 0;
    c.gridy = 0;

    add(inputSource_label, c);

    c = new GridBagConstraints();
    c.gridx = 1;
    c.gridy = 0;
    add(inputSource_combo, c);

    c = new GridBagConstraints();
    c.gridx = 0;
    c.gridy = 1;
    add(output_label, c);

    c = new GridBagConstraints();
    c.gridx = 1;
    c.gridy = 1;
    add(output_combo, c);

    c = new GridBagConstraints();
    c.gridx = 0;
    c.gridy = 2;
    c.gridwidth = 2;
    add(button_panel, c);

Centro

Look at the GridBagLayout tutorial. There are GridBagConstraints that control this behavior, specifically the anchor field. Have you tried this? Has it not worked? If not, please show code else we won't know what you're doing wrong. – Residentiary

Oh no, GridBag again. Why you people use layout manager that was designed for computerised Swing builders? – Underglaze

You can notice that when you do GridBag, the code gets VEEEEERY long and unreadable, filled with constants everywhere. So instead of GridBag, you can try to build a hierarchy of panels using Border, Box and Flow layout. You will get 10% code length and the behaviour will be clear. – Underglaze

@Hovercraft, sorry was not attentive enough. – Centro

@Jakub I have 3 lines per each control; with panels I would have additional lines for subpanels creation. – Centro

Yes... see what happens when you resize? All components get equal space. You might not want this, you might want to keep labels at the same size and resize only inputs. – Underglaze

"I have 3 lines per each control; with panels I would have additional lines for subpanels creation." Sure it would. But if it takes 2 lines to create/add the sub-panel, there are 3 sub-panels, and 20 controls, you are spending an extra (1 versus 3 leaves 2) 60 lines to add the controls to GBL, over 6 LOC to create the panels and 20 lines to add the controls, for a total of 26 LOC. That means creating sub-panels will be 34 lines shorter overall code. – Palaearctic

@Jakub, also what you do to correspond vertical and horizontal positions of logically correspondent controls? – Centro

@Andrew, and what about corresponding? If I wish to have logically gridded controls with rows and columns, how I would correspond them in adjacent panels? – Centro

It depends how your want the GUI to both look & resize. Can you provide 2 ASCII art or drawn images to illustrate? Possibly a GroupLayout would be best if you need to align (guessing that is what you mean by 'corresponding') elements with one another. Also, for better help sooner post an SSCCE. – Palaearctic

Hm, I mentioned the GridBagConstraint.anchor field, but you've seemed to have ignored my recommendation. Why? – Residentiary

I have posted the code in my answer. – Underglaze

@Hovercraft, no I saw it and already used it. – Centro

@Dims: I did not see it used in your posted code. – Residentiary

@Hovercraft, I posted a code to support discussion what is better -- panels or grids, so I posted original code there, before introducing anchors – Centro

Answer 1

When using GridBagLayout for a tabular display of JLabel : JTextField, I like to have a method that makes my GridBagConstraints for me based on the x, y position. For example something like so:

   private GridBagConstraints createGbc(int x, int y) {
      GridBagConstraints gbc = new GridBagConstraints();
      gbc.gridx = x;
      gbc.gridy = y;
      gbc.gridwidth = 1;
      gbc.gridheight = 1;

      gbc.anchor = (x == 0) ? GridBagConstraints.WEST : GridBagConstraints.EAST;
      gbc.fill = (x == 0) ? GridBagConstraints.BOTH
            : GridBagConstraints.HORIZONTAL;

      gbc.insets = (x == 0) ? WEST_INSETS : EAST_INSETS;
      gbc.weightx = (x == 0) ? 0.1 : 1.0;
      gbc.weighty = 1.0;
      return gbc;
   }

The following code makes a GUI that looks like this:

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.util.HashMap;
import java.util.Map;

import javax.swing.*;

public class GridBagEg {
   private static void createAndShowGui() {
      PlayerEditorPanel playerEditorPane = new PlayerEditorPanel();

      int result = JOptionPane.showConfirmDialog(null, playerEditorPane,
            "Edit Player", JOptionPane.OK_CANCEL_OPTION,
            JOptionPane.PLAIN_MESSAGE);
      if (result == JOptionPane.OK_OPTION) {
         // TODO: do something with info

         for (PlayerEditorPanel.FieldTitle fieldTitle : 
            PlayerEditorPanel.FieldTitle.values()) {
            System.out.printf("%10s: %s%n", fieldTitle.getTitle(),
                  playerEditorPane.getFieldText(fieldTitle));
         }
      }
   }

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

@SuppressWarnings("serial")
class PlayerEditorPanel extends JPanel {
   enum FieldTitle {
      NAME("Name"), SPEED("Speed"), STRENGTH("Strength");
      private String title;

      private FieldTitle(String title) {
         this.title = title;
      }

      public String getTitle() {
         return title;
      }
   };

   private static final Insets WEST_INSETS = new Insets(5, 0, 5, 5);
   private static final Insets EAST_INSETS = new Insets(5, 5, 5, 0);
   private Map<FieldTitle, JTextField> fieldMap = new HashMap<FieldTitle, JTextField>();

   public PlayerEditorPanel() {
      setLayout(new GridBagLayout());
      setBorder(BorderFactory.createCompoundBorder(
            BorderFactory.createTitledBorder("Player Editor"),
            BorderFactory.createEmptyBorder(5, 5, 5, 5)));
      GridBagConstraints gbc;
      for (int i = 0; i < FieldTitle.values().length; i++) {
         FieldTitle fieldTitle = FieldTitle.values()[i];
         gbc = createGbc(0, i);
         add(new JLabel(fieldTitle.getTitle() + ":", JLabel.LEFT), gbc);
         gbc = createGbc(1, i);
         JTextField textField = new JTextField(10);
         add(textField, gbc);

         fieldMap.put(fieldTitle, textField);
      }
   }

   private GridBagConstraints createGbc(int x, int y) {
      GridBagConstraints gbc = new GridBagConstraints();
      gbc.gridx = x;
      gbc.gridy = y;
      gbc.gridwidth = 1;
      gbc.gridheight = 1;

      gbc.anchor = (x == 0) ? GridBagConstraints.WEST : GridBagConstraints.EAST;
      gbc.fill = (x == 0) ? GridBagConstraints.BOTH
            : GridBagConstraints.HORIZONTAL;

      gbc.insets = (x == 0) ? WEST_INSETS : EAST_INSETS;
      gbc.weightx = (x == 0) ? 0.1 : 1.0;
      gbc.weighty = 1.0;
      return gbc;
   }

   public String getFieldText(FieldTitle fieldTitle) {
      return fieldMap.get(fieldTitle).getText();
   }

}

In this example, I display the JPanel in a JOptionPane, but it could just as easily be displayed in a JFrame or JApplet or JDialog or ...

Residentiary

my nipples explode with delight – Ancell

care to add the missing PlayerEditorPanel() code so my nipples can do likewise? – Dionysiac

Beautifully aligned, I am speechless (clapping hands). – Humiliate

createGbc method very useful, thanks for answer – Devastate

Answer 2

For example

public class DimsPanel extends JPanel
{
    public static void main(String[] args){
        JFrame main = new JFrame("Dims");
        JPanel myPanel = new DimsPanel();
        main.setContentPane(myPanel);
        main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        main.setSize(400, 400);
        main.setLocationRelativeTo(null);
        main.setVisible(true);
    }

    JButton ok_button = new JButton("OK"), cancel_button = new JButton("Cancel");
    JLabel inputSource_label = new JLabel("Input source:"), 
                output_label = new JLabel("Output:");
    JComboBox inputSource_combo = new JComboBox(new String[]{"A", "B", "C"}), 
                output_combo = new JComboBox(new String[]{"A", "B", "C"});

    public DimsPanel(){
        super(new BorderLayout());
        Box main = new Box(BoxLayout.Y_AXIS);

        Dimension labelsWidth = new Dimension(100, 0);
        JPanel inputPanel = new JPanel(new BorderLayout()); 
        inputSource_label.setPreferredSize(labelsWidth);
        inputPanel.add(inputSource_label, BorderLayout.WEST);
        inputPanel.add(inputSource_combo);

        JPanel outputPanel = new JPanel(new BorderLayout()); 
        output_label.setPreferredSize(labelsWidth);
        outputPanel.add(output_label, BorderLayout.WEST);
        outputPanel.add(output_combo);
        // button panel
        JPanel button_panel = new JPanel();
        button_panel.add(ok_button);
        button_panel.add(cancel_button);

        main.add(inputPanel);
        main.add(outputPanel);

        add(main, BorderLayout.NORTH);
        add(button_panel);
    }
}

You can run and see it. Resizing works like a charm and the layout code has only 18 lines. The only disadvantage is that you need to specify the width of the labels by hand. If you really don't want to see setPreferredSize() in the code, then be my guest and go with GridBag. But I personally like this code more.

Underglaze