Working With the Layout Manager

Abhishek Dubey
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Article

Introduction

In this article we are going to describe the Java layout manager and its use for setting the components within a container. A layout manager is an object that implements the LayoutManager interface and determines the size and position of the components within a container. There are several AWT and Swing classes providing layout managers for general use.

Followings are gerenral use Layouts

1- BorderLayout
2- BoxLayout
3- FlowLayout
4-CardLayout
5- GridBagLayout
6- GridLayout

Border Layout

In this type of layout components are placed in up to five areas: top, bottom, left, right, and center. All extra space is placed in the center area. Tool bars that are created using JToolBar must be created within a BorderLayout container, if you want to be able to drag and drop the bars away from their starting positions. And every content pane initialized is used by a BarderLayout beacuse the content pane is the main container in all frames. For better understanding see the output of the following example carefully.

Example
import java.awt.BorderLayout;

import java.awt.Container;

import java.awt.Dimension;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JLabel;

public class BorderLayoutDemo

{

public static boolean RIGHT_TO_LEFT = false;

public static void addComponentsToPane(Container contentPane)

{

contentPane.setLayout(new BorderLayout(5,5));

if (!(contentPane.getLayout() instanceof BorderLayout)) {

contentPane.add(new JLabel("Container doesn't use BorderLayout!"));

return;

}

if (RIGHT_TO_LEFT)

{

contentPane.setComponentOrientation(

java.awt.ComponentOrientation.RIGHT_TO_LEFT);

}

JButton jbnSampleButtons = new JButton("Top");

contentPane.add(jbnSampleButtons, BorderLayout.PAGE_START);

jbnSampleButtons = new JButton("CENTER");

jbnSampleButtons.setPreferredSize(new Dimension(200, 100));

contentPane.add(jbnSampleButtons, BorderLayout.CENTER);

jbnSampleButtons = new JButton("Left");

contentPane.add(jbnSampleButtons, BorderLayout.LINE_START);

jbnSampleButtons = new JButton("Bottom");

contentPane.add(jbnSampleButtons, BorderLayout.PAGE_END);

jbnSampleButtons = new JButton("Right");

contentPane.add(jbnSampleButtons, BorderLayout.LINE_END);

}

private static void createAndShowGUI()

{

JFrame.setDefaultLookAndFeelDecorated(true);

JFrame frame = new JFrame("BorderLayout Demo by abhishek");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

addComponentsToPane(frame.getContentPane());

frame.pack();

frame.setVisible(true);

}

public static void main(String[] args) {

javax.swing.SwingUtilities.invokeLater(new Runnable()

{

public void run()

{

createAndShowGUI();

}});

}

}

Output

BoxLayout

The BoxLayout sets the components in a single row or column. It respects the component's requested maximum sizes and also lets you align components.

Example
import java.awt.Dimension;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class BoxLayoutDemo extends JFrame
{
public BoxLayoutDemo()
{
initUI();
}
public final void initUI()
{
JPanel basic = new JPanel();
basic.setLayout(new BoxLayout(basic, BoxLayout.Y_AXIS));
add(basic);
basic.add(Box.createVerticalGlue());
JPanel bottom = new JPanel();
bottom.setAlignmentX(1f);
bottom.setLayout(new BoxLayout(bottom, BoxLayout.X_AXIS));
JButton ok = new JButton("OK");
JButton close = new JButton("Close");
bottom.add(ok);
bottom.add(Box.createRigidArea(new Dimension(5, 0)));
bottom.add(close);
bottom.add(Box.createRigidArea(new Dimension(15, 0)));
basic.add(bottom);
basic.add(Box.createRigidArea(new Dimension(0, 15)));
setTitle("Demo of BoxLayout manager");
setSize(300, 150);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
BoxLayoutDemo ex = new BoxLayoutDemo();
ex.setVisible(true);
}
});
}
}

Output

FlowLayout

It is default the layoutmanager of JPanel. And in this layout components are added in a flow (which means a single row) and if the container size is not sufficient then it adds the component to the next new rows.

Example
import java.awt.ComponentOrientation;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
public class FlowLayoutDemo
{
public static boolean RIGHT_TO_LEFT = false;
public static void addComponents(Container contentPane)
{
if (RIGHT_TO_LEFT)
{
contentPane.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
}
contentPane.setLayout(new FlowLayout());
contentPane.add(new JLabel("Label add no 1"));
contentPane.add(new JButton("Button add no 2"));
contentPane.add(new JCheckBox("JCheckBox add no 3"));
contentPane.add(new JTextField("Example made by abhishek"));
contentPane.add(new JButton("Button add no 5"));
}
private static void createAndShowGUI()
{
JFrame.setDefaultLookAndFeelDecorated(true);
JFrame frame = new JFrame("FlowLayout Source Demo")
{
public Dimension getMinimumSize()
{
Dimension prefSize = getPreferredSize();
return new Dimension(100, prefSize.height);
}
};
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
addComponents(frame.getContentPane());
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args)
{
javax.swing.SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}
});
}
}

Output

CardLayout

The CardLayout is often controlled by a combobox, which means its look and feel depends on the slection of a comboBox item. You can use a tabbed pane as an alternative of card layout.The CardLayout class lets you implement an area that contains different components at different times.

Example
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class CardLayoutDemo extends JFrame
{
private int currentCard = 1;
private JPanel cardPanel;
private CardLayout cl;
public CardLayoutDemo()
{
setTitle("Card Layout Example");
setSize(300, 150);
cardPanel = new JPanel();
cl = new CardLayout();
cardPanel.setLayout(cl);
JPanel p1 = new JPanel();
JPanel p2 = new JPanel();
JPanel p3 = new JPanel();
JPanel p4 = new JPanel();
JLabel lab1 = new JLabel("CardLayout1");
JLabel lab2 = new JLabel("CardLayout2");
JLabel lab3 = new JLabel("CardLayout3");
JLabel lab4 = new JLabel("CardLayout4");
p1.add(lab1);
p2.add(lab2);
p3.add(lab3);
p4.add(lab4);
cardPanel.add(p1, "1");
cardPanel.add(p2, "2");
cardPanel.add(p3, "3");
cardPanel.add(p4, "4");
JPanel buttonPanel = new JPanel();
JButton b1 = new JButton("Previous");
JButton b2 = new JButton("Next");
buttonPanel.add(b1);
buttonPanel.add(b2);
b1.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent arg0)
{

if (currentCard > 1)

{

currentCard -= 1;

cl.show(cardPanel, "" + (currentCard));

}

});

b2.addActionListener(new ActionListener()

{

public void actionPerformed(ActionEvent arg0)

{

if (currentCard < 4)

{

currentCard += 1;

cl.show(cardPanel, "" + (currentCard));

}}

});

getContentPane().add(cardPanel, BorderLayout.NORTH);

getContentPane().add(buttonPanel, BorderLayout.SOUTH);

}

public static void main(String[] args)

{

CardLayoutDemo cl = new CardLayoutDemo();

cl.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

cl.setVisible(true);

}

Output

After clicking on next button

GridBagLayout

GridBagLayout is a flexible and sophisticated layout manager. It sets the components into a grid of cells and it allows components to span more then one cell. And the row within grids can have different heights.

Example
import java.awt.*;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JTextField;
public class GridBagLayoutDemo
{
public static void addComponentsToPane(Container pane)
{
JButton jbnButton;
pane.setLayout(new GridBagLayout());
GridBagConstraints gBC = new GridBagConstraints();
gBC.fill = GridBagConstraints.HORIZONTAL;
jbnButton = new JButton("Button 1");
gBC.weightx = 0.5;
gBC.gridx = 0;
gBC.gridy = 0;
pane.add(jbnButton, gBC);
JTextField jtf = new JTextField("TextField 1");
gBC.gridx = 2;
gBC.gridy = 0;
jtf.setEditable(false);
pane.add(jtf, gBC);
jbnButton = new JButton("Button 3");
gBC.gridx = 2;
gBC.gridy = 0;
pane.add(jbnButton, gBC);
jbnButton = new JButton("Button 4");
gBC.ipady = 40; //This component has more breadth compared to
other buttons
gBC.weightx = 0.0;
gBC.gridwidth = 3;
gBC.gridx = 0;
gBC.gridy = 1;
pane.add(jbnButton, gBC);
JComboBox jcmbSample = new JComboBox(new String[]{"ComboBox 1", "hi", "hello"});
gBC.ipady = 0;
gBC.weighty = 1.0;
gBC.anchor = GridBagConstraints.PAGE_END;
gBC.insets = new Insets(10,0,0,0); //Padding
gBC.gridx = 1;
gBC.gridwidth = 2;
gBC.gridy = 2;
pane.add(jcmbSample, gBC);
}
private static void createAndShowGUI()
{
JFrame.setDefaultLookAndFeelDecorated(true);
JFrame frame = new JFrame("GridBagLayout Source Demo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
addComponentsToPane(frame.getContentPane());
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args)
{
javax.swing.SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}});
}
}

Output

When the window size is small:

When the window size is large:

GridLayout

In a GridLayout each component takes all the available space with in its cell and each cell size is exactly the same size. In the grid layout if you change your frame or window size then its cell size changes. The cell takes the maximum value possible.

Example
import java.awt.*;
import javax.swing.*;
public class GridLayoutDemo
{
public final static boolean RIGHT_TO_LEFT = false;
public static void addComponentsToPane(Container contentPane)
{
if (RIGHT_TO_LEFT)
{
contentPane.setComponentOrientation(
ComponentOrientation.RIGHT_TO_LEFT);
}
contentPane.setLayout(new GridLayout(0,2));
contentPane.add(new JLabel("My label "));
contentPane.add(new JButton("My button"));
contentPane.add(new JCheckBox(" MY CheckBox"));
contentPane.add(new JTextField("this developed by abhishek"));
contentPane.add(new JButton("my button 1"));
}
private static void createAndShowGUI()
{
JFrame.setDefaultLookAndFeelDecorated(true);
JFrame frame = new JFrame("GridLayout Source Demo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
addComponentsToPane(frame.getContentPane());
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args)
{
javax.swing.SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}
});
}
}