Layout Managers in Java : Part 2

Introduction

This article contains information about Layout Managers beyond that discussed in Part 1.

Layout Managers

For previously discussed Layout Managers, follow the link given below:

http://www.c-sharpcorner.com/UploadFile/9a9e6f/layout-managers-in-java-part-1/

Card Layout Manager

The card layout class manages two or more components that share the same display space in such a way that only one component is visible at a time.

Basically, each card is like a playing card in a stack, where only the top card is visible at any time, that's why it is known as the Card Layout Manager. Each card is normally a panel that can use any layout manager.

Example

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

public class Card extends JFrame implements ActionListener {
   private CardLayout cardManager;
   private JPanel deck;
   private JButton controls[];
   private String names[] = { "First card", "Next card", "Previous card", "Last card" };

   public Card()
   {
      super( "CardLayout manager" );

      Container c = getContentPane();

      // create the JPanel with CardLayout
      deck = new JPanel();
      cardManager = new CardLayout();
      deck.setLayout( cardManager );

      // set up card1 and add it to JPanel deck
      JLabel label1 = new JLabel( "card one", SwingConstants.CENTER );
      JPanel card1 = new JPanel();
      card1.setBackground( Color.GREEN);
      card1.add( label1 );
      deck.add( card1, label1.getText() ); // add card to deck

      // set up card2 and add it to JPanel deck
      JLabel label2 = new JLabel( "card two", SwingConstants.CENTER );
      JPanel card2 = new JPanel();
      card2.setBackground( Color.blue );
      card2.add( label2 );
      deck.add( card2, label2.getText() ); // add card to deck

      // set up card3 and add it to JPanel deck
      JLabel label3 = new JLabel( "card three" ,SwingConstants.CENTER);
      JPanel card3 = new JPanel();
      card3.setBackground( Color.RED);
      card3.add( label3);
      deck.add( card3, label3.getText() ); // add card to deck

      // create and layout buttons that will control deck
      JPanel buttons = new JPanel();
      buttons.setLayout( new GridLayout( 2, 2 ) );
      controls = new JButton[ names.length ];

      for ( int i = 0; i < controls.length; i++ ) {
         controls[ i ] = new JButton( names[ i ] );
         controls[ i ].addActionListener( this );
         buttons.add( controls[ i ] );
      }

      // add JPanel deck and JPanel buttons to the applet
      c.add( buttons, BorderLayout.WEST );
      c.add( deck, BorderLayout.EAST );

      setSize( 450,300 );
      show();
   }

   public void actionPerformed( ActionEvent e )
   {
      if ( e.getSource() == controls[ 0 ] )
      cardManager.first( deck ); // show first card
      else if ( e.getSource() == controls[ 1 ] )
      cardManager.next( deck ); // show next card
      else if ( e.getSource() == controls[ 2 ] )
      cardManager.previous( deck ); // show previous card
      else if ( e.getSource() == controls[ 3 ] )
      cardManager.last( deck ); // show last card
   }

   public static void main( String args[] )
   {
      Card cardDeckDemo = new Card();

      cardDeckDemo.addWindowListener(
      new WindowAdapter() {
         public void windowClosing( WindowEvent e )
         {
            System.exit( 0 );
         }
      });
   }
}

Output

 

Outputs after clicking "Next card" and "Last card" and then "Previous card":

Next card

Last card

Previous card will be the next card, in other words card two.

GridBag Layout Manager

The GridBag layout manages the components in rows or columns that allow specified components to span multiple rows and columns. Not all the rows and columns have the same height and width.

This is the most complex layout manager since it specifies the size and position characteristics of its components by specifying constraints for each component.

Example

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

public class GridBag extends JFrame {
   private Container container;
   private GridBagLayout gbLayout;
   private GridBagConstraints gbConstraints;

   public GridBag()
   {
      super( "GridBagLayout manager" );

      container = getContentPane();
      gbLayout = new GridBagLayout();
      container.setLayout( gbLayout );

      // instantiate gridbag constraints
      gbConstraints = new GridBagConstraints();

      JTextArea ta = new JTextArea( "TextField1", 5, 10 );
      JTextArea tx = new JTextArea( "TextField2", 2, 2 );
      String names[] = { "Laptop", "Palmtop", "Tablet", "Mobile" };
      JComboBox cb = new JComboBox( names );
      JTextField tf = new JTextField( "TextField" );
      JButton b1 = new JButton( "Button 1" );
      JButton b2 = new JButton( "Button 2" );
      JButton b3 = new JButton( "Button 3" );

      // text area
      // weightx and weighty are both 0: the default
      // anchor for all components is CENTER: the default
      gbConstraints.fill = GridBagConstraints.BOTH;
      addComponent( ta, 0, 0, 1, 3 );

      // button b1
      // weightx and weighty are both 0: the default
      gbConstraints.fill = GridBagConstraints.HORIZONTAL;
      addComponent( b1, 0, 1, 2, 1 );

      // combo box
      // weightx and weighty are both 0: the default
      // fill is HORIZONTAL
      addComponent( cb, 2, 1, 2, 1 );

      // button b2
      gbConstraints.weightx = 1000; // can grow wider
      gbConstraints.weighty = 1; // can grow taller
      gbConstraints.fill = GridBagConstraints.BOTH;
      addComponent( b2, 1, 1, 1, 1 );

      // button b3
      // fill is BOTH
      gbConstraints.weightx = 0;
      gbConstraints.weighty = 0;
      addComponent( b3, 1, 2, 1, 1 );

      // textfield
      // weightx and weighty are both 0: fill is BOTH
      addComponent( tf, 3, 0, 2, 1 );

      // textarea
      // weightx and weighty are both 0: fill is BOTH
      addComponent( tx, 3, 2, 1, 1 );

      setSize( 350, 200 );
      show();
   }

   // addComponent is programmer defined
   private void addComponent( Component c, int row, int column, int width, int height )
   {
      // set gridx and gridy
      gbConstraints.gridx = column;
      gbConstraints.gridy = row;

      // set gridwidth and gridheight
      gbConstraints.gridwidth = width;
      gbConstraints.gridheight = height;

      // set constraints
      gbLayout.setConstraints( c, gbConstraints );
      container.add( c ); // add component
   }

   public static void main( String args[] )
   {
      GridBag app = new GridBag();

      app.addWindowListener(
      new WindowAdapter() {
         public void windowClosing( WindowEvent e )
         {
            System.exit( 0 );
         }
      });
   }
}

Output

For further read about the topic , please go through the below link.

http://www.c-sharpcorner.com/UploadFile/9a9e6f/layout-managers-in-java-part-3/