Swing Layouts
GridBag Layout
We will probably use the GridBag layout most often to layout complicated panels. Here is a list of what the GridBag layout does.
* We can specify which cell we want each component to go in and the component's position on the panel.
* If a component doesn't fill its allotted area, we can tell the GridBag how to position the component within the area.
* The rows and columns don't all have to be the same size. In addition, it automatically adjust the width of each column and the height of each row.
* We can create component that span multiple rows or columns.
* We can tell the GridBag to stretch a component to fill the entire space allotted to it.
For all the GridBag layout constructors and methods, look at the link below " Swing Method & Constructor Table."
Creating a GridBag Layout
JPanel panel = new JPanel();
panel.setLayout(new GridBagLayout());
With a panel that uses a GridBag layout, the add method accepts two parameters: the component to add and a GridBagConstraints object.
GridBagConstraints: It specifies where to place the component in the grid.
When using the GridBagConstraints, we call its constructor and then set any of the fields that we want.
/*
This is a GridBagLyout Manager
It demonstrate the use of GridBagConstraints
JRadioButton, JCheckBox and JTextField
*
*/
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class GridBag extends
JFrame
{
JTextField nametxt, phonetxt, emailtxt;
JLabel name, phone, email;
JButton ok, exit;
JRadioButton day, week, month, small, large;
JCheckBox slow, fast, nextday;
JPanel panel;
public GridBag()
{
// Sets the title of the window
setTitle("GridBag Layout Manager");
// Sets the start location of the
window
setLocationRelativeTo(null);
// Sets the action when the window is
close
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create a panel and set the layout
to GridBagLayout
panel = new JPanel();
panel.setLayout(new GridBagLayout());
// Create the labels
name = new JLabel("Name");
phone = new JLabel("Phone");
email = new JLabel("E-Mail");
// Adds the label to
GridBagConstraints
addItem(panel, name, 0, 0, 1, 1,
GridBagConstraints.EAST);
addItem(panel, phone, 0, 1, 1, 1,
GridBagConstraints.EAST);
addItem(panel, email, 0, 2, 1, 1,
GridBagConstraints.EAST);
// Create the text field
nametxt = new JTextField(20);
phonetxt = new JTextField(15);
emailtxt = new JTextField(25);
// Add the text field to the
GridBagConstraints
addItem(panel, nametxt, 1, 0, 2, 1,
GridBagConstraints.WEST);
addItem(panel, phonetxt, 1, 1, 1, 1,
GridBagConstraints.WEST);
addItem(panel, emailtxt, 1, 2, 2, 1,
GridBagConstraints.WEST);
// Creates a vertical box to organize
the buttons
Box timebox = Box.createVerticalBox();
// Creates the radio buttons
day = new JRadioButton("Day");
week = new JRadioButton("Week");
month = new JRadioButton("Month");
// Group the buttons together
ButtonGroup timegroup = new
ButtonGroup();
timegroup.add(day);
timegroup.add(week);
timegroup.add(month);
// Add the buttons to the Box
timebox.add(day);
timebox.add(week);
timebox.add(month);
// Sets the bevelBroder title
timebox.setBorder(BorderFactory.createTitledBorder("Time Frame"));
// Adds the box into the
GridBagConstraints
addItem(panel, timebox, 0, 3, 1, 1,
GridBagConstraints.NORTH);
// Create a new box to handles the
size
Box sizebox = Box.createVerticalBox();
// Create the radio buttons
small = new JRadioButton("Small");
large = new JRadioButton("Large");
// Group the buttons together
ButtonGroup sizegroup = new
ButtonGroup();
sizegroup.add(small);
sizegroup.add(large);
// Add the buttons to the box
sizebox.add(small);
sizebox.add(large);
// Create a bevelBorder title
sizebox.setBorder(BorderFactory.createTitledBorder("Size"));
// Adds to the GridBagConstraints
addItem(panel, sizebox, 1, 3, 1, 1,
GridBagConstraints.NORTH);
// Creates another box layout
Box speed =Box.createVerticalBox();
// Create JCheckBox buttons
slow = new JCheckBox("Slow");
fast = new JCheckBox("Fast");
nextday = new JCheckBox("Next Day");
// Group the buttons together
ButtonGroup speedgroup = new
ButtonGroup();
speedgroup.add(slow);
speedgroup.add(fast);
speedgroup.add(nextday);
// Add the buttons to the box
speed.add(slow);
speed.add(fast);
speed.add(nextday);
// Create bevelborder title
speed.setBorder(BorderFactory.createTitledBorder("Speed"));
// Adds to the GridBagConstraints
addItem(panel, speed, 2, 3, 1, 1,
GridBagConstraints.NORTH);
// Create the buttons
ok = new JButton("OK");
exit = new JButton("EXIT");
// Create a horizontal box to hold
the buttons
Box buttonbox =
Box.createHorizontalBox();
// Add the ok button to the box
buttonbox.add(ok);
// Create a space between ok and exit
button
buttonbox.add(Box.createHorizontalStrut(50));
// Add the exit button to the box
buttonbox.add(exit);
// Add the button tp the
GridBagConstraints
addItem(panel, buttonbox, 2, 4, 1, 1,
GridBagConstraints.NORTH);
// Add the panel to the content pane
add(panel);
// Pack everything up
pack();
// Sets the window to be visible
setVisible(true);
}
/*
Here is the void method of addItem
It sets the height, width, location,
and align of the components
*
*/
public void addItem(JPanel p, JComponent c, int x, int y, int
wid, int hei, int align)
{
// Creates a GridBagConstraints
GridBagConstraints grid = new
GridBagConstraints();
// Sets the position of the
components
grid.gridx = x;
grid.gridy = y;
// Sets the number of columns & rows
span by the components
grid.gridwidth = wid;
grid.gridheight = hei;
// Tells the grid layout how to
apportion space
grid.weightx = 100.00;
grid.weighty = 100.00;
// It indicates how much space to use
as padding around each component
grid.insets = new Insets(5,5,5,5);
// Indicates where to place the
component if it doesn't fill the space
grid.anchor = align;
// Indicates whether to stretch the
object to fill available space or not
grid.fill = GridBagConstraints.NONE;
// adds to the panel
p.add(c,grid);
}
public static void main(String[] args)
{
new GridBag();
}
}
ClickHere to download GridBag.java
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