Looking for general method for GridBagLayout component creation

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I use GridBagLyout quite a lot, but like many others before me, I quickly found out it can be quite verbose. There are many examples on the web of how users wrote utility methods and/or classes to help them generate GBL code. I’ll show you what I do.

1) First, I created 2 enums that are wrappers for the anchor and fill GridBagConstraints fields. I prefer the type checking of enums vs. ints, and it also allows me to write more concise code (as you’ll see later). And yes, I still use the older “directional” values for Anchor. I could never quite get used to the preferred values of PAGE_START and the like. Use whatever you prefer.

Anchor.java:

package gbl;

import java.awt.*;

/**
 * Convenience enum that aliases out all possible values for the
 * GridBagConstraints anchor property.
 */
public enum Anchor
{
  NORTH(GridBagConstraints.NORTH),
  SOUTH(GridBagConstraints.SOUTH),
  EAST(GridBagConstraints.EAST),
  WEST(GridBagConstraints.WEST),
  NORTHEAST(GridBagConstraints.NORTHEAST),
  NORTHWEST(GridBagConstraints.NORTHWEST),
  SOUTHEAST(GridBagConstraints.SOUTHEAST),
  SOUTHWEST(GridBagConstraints.SOUTHWEST),
  CENTER(GridBagConstraints.CENTER);

  private int constraint;

  private Anchor(int gbConstraint)
  {
    constraint = gbConstraint;
  }

  public int getConstraint()
  {
    return constraint;
  }
}

Fill.java:

package gbl;

import java.awt.*;

/**
 * Convenience enum that aliases out all possible values for the
 * GridBagConstraints fill property.
 */
public enum Fill
{
  NONE(GridBagConstraints.NONE),
  HORIZONTAL(GridBagConstraints.HORIZONTAL),
  VERTICAL(GridBagConstraints.VERTICAL),
  BOTH(GridBagConstraints.BOTH);

  private int constraint;

  private Fill(int gbConstraint)
  {
    constraint = gbConstraint;
  }

  public int getConstraint()
  {
    return constraint;
  }
}

2) Then, I created a subclass of GridBagConstraints that allowed me “chain” the properties only as I need them, while utilizing common defaults:

GBConstraints.java:

package gbl;

import java.awt.*;

/**
 * Convenience class to simplify the creation of a GridBagConstraints object.
 */
public class GBConstraints extends GridBagConstraints
{
  public GBConstraints(int gridX, int gridY)
  {
    super();

    this.gridx = gridX;
    this.gridy = gridY;

    this.gridwidth = 1;
    this.gridheight = 1;
    this.weightx = 0;
    this.weighty = 0;
    this.anchor = NORTHWEST;              // old default was CENTER
    this.fill = NONE;
    this.insets = new Insets(1,2,1,2);    // old default was (0,0,0,0)
    this.ipadx = 1;                       // old default was 0
    this.ipady = 1;                       // old default was 0
  }

  public GBConstraints anchor(Anchor anchor)
  {
    this.anchor = anchor.getConstraint();
    return this;
  }

  public GBConstraints fill(Fill fill)
  {
    this.fill = fill.getConstraint();

    /*
     * As a convenience, set the weights appropriately since these values are
     * almost always used in tandem with the given Fill. The caller can always
     * call the weight(...) method later if these defaults aren't desired. 
     */
    switch (fill)
    {
      case HORIZONTAL:
        this.weightx = 1;
        this.weighty = 0;
        break;
      case VERTICAL:
        this.weightx = 0;
        this.weighty = 1;
        break;
      case BOTH:
        this.weightx = 1;
        this.weighty = 1;
        break;
      default:
        this.weightx = 0;
        this.weighty = 0;
        break;
    }

    return this;
  }

  public GBConstraints insets(int length)
  {
    return insets(length, length, length, length);
  }

  public GBConstraints insets(int top, int left, int bottom, int right)
  {
    this.insets = new Insets(top, left, bottom, right);
    return this;
  }

  public GBConstraints ipad(int ipadX, int ipadY)
  {
    this.ipadx = ipadX;
    this.ipady = ipadY;
    return this;
  }

  public GBConstraints span(int gridWidth, int gridHeight)
  {
    this.gridwidth = gridWidth;
    this.gridheight = gridHeight;
    return this;
  }

  public GBConstraints spanX(int gridWidth)
  {
    this.gridwidth = gridWidth;
    return this;
  }

  public GBConstraints spanY(int gridHeight)
  {
    this.gridheight = gridHeight;
    return this;
  }

  public GBConstraints weight(double weightX, double weightY)
  {
    this.weightx = weightX;
    this.weighty = weightY;
    return this;
  }

  public GBConstraints weightX(double weightX)
  {
    this.weightx = weightX;
    return this;
  }

  public GBConstraints weightY(double weightY)
  {
    this.weighty = weightY;
    return this;
  }
}

3) Putting it all together, here’s a demo that shows how to use the above classes. This greatly simplifies using GridBagLayout, IMHO. Side note: I normally stay away from static imports, but I like it in this situation.

Demo:

package gbl;

import static gbl.Anchor.*;
import static gbl.Fill.*;

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

public class GridBagDemo implements Runnable
{
  public static void main(String[] args)
  {
    SwingUtilities.invokeLater(new GridBagDemo());
  }

  public void run()
  {
    JLabel lblFirst  = new JLabel("First Name");
    JLabel lblLast   = new JLabel("Last Name");
    JLabel lblStreet = new JLabel("Street");
    JLabel lblCity   = new JLabel("City");
    JLabel lblState  = new JLabel("State");
    JLabel lblZip    = new JLabel("ZIP");
    JLabel lblNotes  = new JLabel("Notes");

    JTextField txfFirst  = new JTextField(15);
    JTextField txfLast   = new JTextField(20);
    JTextField txfStreet = new JTextField(40);
    JTextField txfCity   = new JTextField(15);
    JTextField txfState  = new JTextField(5);
    JTextField txfZip    = new JTextField(10);

    JTextArea txaNotes = new JTextArea(5, 50);
    JScrollPane scrNotes = new JScrollPane(txaNotes);
    scrNotes.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

    Component spacer1 = Box.createHorizontalStrut(5);
    Component spacer2 = Box.createHorizontalStrut(5);

    JPanel panel = new JPanel(new GridBagLayout());
    panel.add(spacer1,   new GBConstraints(0,0));
    panel.add(lblFirst,  new GBConstraints(0,1));
    panel.add(txfFirst,  new GBConstraints(1,1));
    panel.add(lblLast,   new GBConstraints(2,1));
    panel.add(txfLast,   new GBConstraints(3,1).spanX(3).fill(HORIZONTAL));
    panel.add(lblStreet, new GBConstraints(0,2));
    panel.add(txfStreet, new GBConstraints(1,2).spanX(5).fill(HORIZONTAL));
    panel.add(lblCity,   new GBConstraints(0,3));
    panel.add(txfCity,   new GBConstraints(1,3));
    panel.add(lblState,  new GBConstraints(2,3).anchor(EAST));
    panel.add(txfState,  new GBConstraints(3,3));
    panel.add(lblZip,    new GBConstraints(4,3));
    panel.add(txfZip,    new GBConstraints(5,3).fill(HORIZONTAL));
    panel.add(lblNotes,  new GBConstraints(0,4));
    panel.add(scrNotes,  new GBConstraints(1,4).spanX(5).fill(BOTH));
    panel.add(spacer2,   new GBConstraints(0,5));

    JFrame frame = new JFrame("Grid Bag Demo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.add(new JScrollPane(panel), BorderLayout.CENTER);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
  }
}

Again, this is just one of many ways you’ll find online. Hope this helps.

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