CS 596 Java Programming Fall Semester, 1998 Events, Containers
	To Lecture Notes Index © 1998, All Rights Reserved, SDSU & Roger Whitney San Diego State University -- This page last updated 21-Dec-98

Reference:

AWT Events

Event Listening Example
Event Sequence
Consuming Events

Containers

Panels
Canvas

Reference:

Q-nov24 1min, S-nov25 51secs Doc 29, Events, Containers Slide # 2

AWT Events

Q-nov24 3mins, S-nov25 2mins Doc 29, Events, Containers Slide # 3

S-nov25 33secs, S-nov25 57secs Doc 29, Events, Containers Slide # 4

Event Listening Example

import java.awt.*;
import java.awt.event.*;
class ButtonSnooper implements ActionListener{
   public void actionPerformed( ActionEvent event )  {
      System.out.println( "Button pressed");
   }
}
class MouseSnooper implements MouseListener {
   public void mouseClicked(MouseEvent event) {
      System.out.println( "Mouse clicked" );
   }
      
   public void mousePressed(MouseEvent event) {
      System.out.println( "Mouse pressed" );
   }
   public void mouseReleased(MouseEvent event) {
      System.out.println( "Mouse released" );
   }
   public void mouseEntered(MouseEvent event) {
      Button currentButton = (Button) event.getComponent();
      System.out.println( "Mouse entered "  + currentButton.getLabel() );
   }
   public void mouseExited(MouseEvent event) {
      System.out.println( "Mouse exited" );
   }
}
Q-nov24 2mins, S-nov25 2mins Doc 29, Events, Containers Slide # 5

class MouseMotionSnooper implements MouseMotionListener {
   public void mouseDragged(MouseEvent event) {
      System.out.println( "Mouse dragged" );
   }
      
   public void mouseMoved(MouseEvent event) {
      System.out.println( "Mouse moved, is at: " + event.getPoint() );
   }
}
class FocusSnooper implements FocusListener {
   public void focusGained(FocusEvent event) {
      Button currentButton = (Button) event.getComponent();
      
      System.out.print( currentButton.getLabel() + " gained focus" );
      if ( event.isTemporary() )
         System.out.println( ": temporary");
      else
         System.out.println();
   }
      
   public void focusLost(FocusEvent event) {
      Button currentButton = (Button) event.getComponent();
      
      System.out.print( currentButton.getLabel() + " lost focus" );
      if ( event.isTemporary() )
         System.out.println( ": temporary");
      else
         System.out.println();
   }
}
Q-nov24 50secs, S-nov25 34secs Doc 29, Events, Containers Slide # 6

class KeySnooper implements KeyListener {
   public void keyPressed(KeyEvent event) {
      System.out.println( "Key pressed" );
   }
   public void keyReleased(KeyEvent event) {
      System.out.println( "Key released" );
   }
   public void keyTyped(KeyEvent event) {
      System.out.println( "Key typed: " + event.getKeyChar() 
         + " with " + KeyEvent.getKeyModifiersText( event.getModifiers() ) );
   }
}
class ComponentSnooper implements ComponentListener {
   public void componentHidden(ComponentEvent event) {
      Button currentButton = (Button) event.getComponent();
      System.out.println( "Component " + currentButton.getLabel() +
         " hidden" );
   }
   public void componentMoved(ComponentEvent event) {
      Button currentButton = (Button) event.getComponent();
      System.out.println( "Component " + currentButton.getLabel() +
         " moved" );
   }
   public void componentResized(ComponentEvent event) {
      Button currentButton = (Button) event.getComponent();
      System.out.println( "Component " + currentButton.getLabel() +
         " resized" );
   }
   public void componentShown(ComponentEvent event) {
      Button currentButton = (Button) event.getComponent();
      System.out.println( "Component " + currentButton.getLabel() +
         " shown" );
   }
}
Q-nov24 54secs, S-nov25 25secs Doc 29, Events, Containers Slide # 7

class  EventExample  extends Frame
   {
   Button a = new Button( "A" );
   Button b = new Button( "B" );
   
   public EventExample( int  widthInPixels, int heightInPixels )
      {
      setTitle( "Event Example" );
      setSize( widthInPixels, heightInPixels );
      add( a, BorderLayout.NORTH );
      add( b, BorderLayout.CENTER );
      
      a.addActionListener( new ButtonSnooper( ) );
      a.addMouseListener( new MouseSnooper( ) );
      a.addMouseMotionListener( new MouseMotionSnooper( ) );
      a.addFocusListener( new FocusSnooper( ) );
      a.addKeyListener( new KeySnooper( ) );
      a.addComponentListener( new ComponentSnooper( ) );
      
      b.addActionListener( new ButtonSnooper( ) );
      b.addMouseListener( new MouseSnooper( ) );
      b.addMouseMotionListener( new MouseMotionSnooper( ) );
      b.addFocusListener( new FocusSnooper( ) );
      b.addKeyListener( new KeySnooper( ) );
      b.addComponentListener( new ComponentSnooper( ) );
      show();
      }
            
   public  static  void  main( String  args[] ){
      EventExample  window = new  EventExample(200, 50);
      }
   }
Q-nov24 2mins, S-nov25 3mins, S-nov25 2mins Doc 29, Events, Containers Slide # 8

Event Sequence

Q-nov24 51secs, S-nov25 1min Doc 29, Events, Containers Slide # 9

Q-nov24 3mins, S-nov25 2mins Doc 29, Events, Containers Slide # 10

Consuming Events

Q-nov24 2mins, S-nov25 4mins Doc 29, Events, Containers Slide # 11

Containers

Panels

import java.awt.*;
class  PanelExample  extends Frame  {
   
   public PanelExample( int  widthInPixels, int heightInPixels ) {
      setTitle( "Panel Example" );
      setSize( widthInPixels, heightInPixels );
      setLayout( new BorderLayout() );
      
      Panel buttonDisplay = new Panel();
      buttonDisplay.setLayout( new FlowLayout() );
      
      for ( int label = 1; label < 6; label++ )
         buttonDisplay.add( new Button( String.valueOf( label )) );
      add( buttonDisplay, BorderLayout.NORTH );
      add( new Button( "Center" ), BorderLayout.CENTER);
      add( new Scrollbar( Scrollbar.VERTICAL ), BorderLayout.EAST );
      add( new Scrollbar( Scrollbar.HORIZONTAL ), BorderLayout.SOUTH );
      show();
   }
   
   public  static  void  main( String  args[] ) {
      new  PanelExample( 175, 100 );
   }
}
Q-nov24 3mins, S-nov25 3mins Doc 29, Events, Containers Slide # 12

Q-nov24 53secs, S-nov25 4mins Doc 29, Events, Containers Slide # 13

Canvas

Creates the peer of the canvas.

Paints the canvas in the default background color.

class SimpleCanvas extends Canvas{
   public void paint( Graphics drawOnMe ){
      int startX = 0;
      int startY = 0;
      int endX = 30;
      int endY = 30;
      drawOnMe.drawLine( startX, startY, endX, endY );
      int width = 5;
      int height = 5;
      drawOnMe.drawOval(  endX, endY, width, height );
      }
   }

Q-nov24 1min, S-nov25 2mins Doc 29, Events, Containers Slide # 14

class  CanvasExample  extends Frame {
   public CanvasExample( int  widthInPixels, int heightInPixels ) {
      setTitle( "Canvas Example" );
      setSize( widthInPixels, heightInPixels );
      setLayout( new BorderLayout() );
      
      Panel buttonDisplay = new Panel();
      buttonDisplay.setLayout( new FlowLayout() );
      
      for ( int label = 1; label < 6; label++ )
         buttonDisplay.add( new Button( String.valueOf( label ) ) );
      add( buttonDisplay, BorderLayout.NORTH );
      add( new SimpleCanvas(), BorderLayout.CENTER );
      add( new Scrollbar( Scrollbar.VERTICAL ), BorderLayout.EAST );
      add( new Scrollbar( Scrollbar.HORIZONTAL ),
               BorderLayout.SOUTH );
      show();
   }
   
   public  static  void  main( String  args[] ) {
      new  CanvasExample( 175, 150 );
   }
}

Q-nov24 56secs, S-nov25 1min Doc 29, Events, Containers Slide # 15

What is Going On Here?

class  CanvasProblem  extends Frame  {
   public CanvasProblem( int  widthInPixels, int heightInPixels ) {
      setTitle( "Canvas Problem" );
      setSize( widthInPixels, heightInPixels );
      setLayout( new BorderLayout() );
      
      Panel buttonDisplay = new Panel();
      buttonDisplay.setLayout( new FlowLayout() );
      
      for ( int label = 1; label < 6; label++ )
         buttonDisplay.add( new Button( String.valueOf( label ) ) );
      add( buttonDisplay, BorderLayout.CENTER );
      add( new SimpleCanvas(), BorderLayout.NORTH );
      add( new Scrollbar( Scrollbar.VERTICAL ), BorderLayout.EAST );
      add( new Scrollbar( Scrollbar.HORIZONTAL ),
               BorderLayout.SOUTH );
      show();
   }
   
   public  static  void  main( String  args[] ) {
      new  CanvasProblem( 175, 150 );
   }
}

Q-nov24 3mins, S-nov25 4mins Doc 29, Events, Containers Slide # 16

North, South respect preferred height, ignores preferred width

East, West respect preferred width, ignores preferred height

Center ignores preferred height and preferred width

Q-nov24 3mins, S-nov25 3mins Doc 29, Events, Containers Slide # 17

class SimpleCanvas extends Canvas{
   Dimension preferredSize;
   
   public SimpleCanvas( int width, int height ) {
      preferredSize = new Dimension( width, height );
   }
   
   public void paint( Graphics drawOnMe ){
      int startX = 0;
      int startY = 0;
      int endX = 30;
      int endY = 30;
      drawOnMe.drawLine( startX, startY, endX, endY );
      int width = 5;
      int height = 5;
      drawOnMe.drawOval(  endX, endY, width, height );
   }
      
   public Dimension preferredSize() {
      return preferredSize;
   }
   public Dimension minimumSize() { return new Dimension( 5, 5 ); }
}

visitors since 23-Nov-98