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

Reference:

Java Foundation Classes (JFC)
Building GUIs - Abstract Window Toolkit (AWT)

Java GUI Applications & NCD Terminals
Event Model

Delegation Event Model
Window Event Example

Overview of AWT Parts
Button Examples

Button Events

Reference:

S-nov16 11mins, Q-nov19 6mins Doc 24, JFC Basics Slide # 2

Java Foundation Classes (JFC)

Abstract Window Toolkit (AWT)

Basic windowing components & structure

Swing Components

Lightweight components providing wide range of options

Java 2D

Full range of 2D operations

Accessibility Framework

Framework for making applications usable by people with impairments. Implementations of the framework to be provided by JavaSoft and third parties

S-nov16 59secs, Q-nov19 3mins Doc 24, JFC Basics Slide # 3

Building GUIs - Abstract Window Toolkit (AWT)

Basic UI things like

Buttons, Checkboxes, Choices,

Lists, Menus, and Text Fields

Scrollbars and Labels

Contain components and containers

Window

Position items in window

Drawing on the screen

S-nov16 11mins, Q-nov19 4mins Doc 24, JFC Basics Slide # 4

Some AWT classes use peers to display and manage a GUI component. For example, when you create a menu object in AWT, the JVM will create a menu using the platform's native menu code. The AWT menu object acts like a wrapper around the menu peer. Messages sent to the AWT menu object are eventually handled by the menu peer. The peer is the item that defines the look and behavior of the menu. This means that the behavior is defined by the platform.

Use Java code to display and manage a GUI component.

A lightweight menu will not use the native peer. It would draw the rectangle around the menu, draw the menu text, etc. At some point, the lightweight menu will use some AWT component to perform some low-level graphic operation, which will use a peer to perform the operation. However, the Java code is used to define the look and behavior of the menu. A lightweight menu can have behavior that is not available on in the platform's native window system.

Look and feel is platform independent

Provides wide arrange of options for look and feel

Ports immediately to any Java supported system

May perform slower than a peer

S-nov16 2mins Doc 24, JFC Basics Slide # 5

S-nov16 3mins, Q-nov19 7mins Doc 24, JFC Basics Slide # 6

import  java.awt.*;
class  HelloApplication  extends  Frame 
   {
   public  void  paint(  Graphics  display  )
      {
      int startX  =  30;
      int startY  =  40;
      display.drawString(  "Hello World", startX, startY  );
      }
   }
class Test
   {
   public  static  void  main( String  args[] )
      {
      HelloApplication  mainWindow = new  HelloApplication();
      int  width  =  150; // in pixels
      int  height  =  80;
      int left = 20; 
      int top = 40;
      mainWindow.setSize( width, height );
      mainWindow.setLocation( left, top);
      mainWindow.setTitle( "Hello" );
      mainWindow.show();
      }
   }

Doc 24, JFC Basics Slide # 7

import  java.awt.*;
class  HelloLabel  extends  Frame 
   {
   public HelloLabel( int left, int top, int width, int height, String title )
      {
      super( title );
      setSize( width, height );
      setLocation( left, top);
      Label hello = new Label( "Hello World", Label.CENTER);
      add( hello, BorderLayout.CENTER  );
      show();
      }
   }
class Test
   {
   public  static  void  main( String  args[] )
      {
      HelloLabel  mainWindow = new  HelloLabel( 20, 40, 150, 80, "Hi Dad");
      }
   }

S-nov16 4mins Doc 24, JFC Basics Slide # 8

Java GUI Applications & NCD Terminals

Doc 24, JFC Basics Slide # 9

Event Model

GUIs must handle events like mouse clicks, mouse movements, scrolling of a window.

Used inheritance-based event model for handling. Your classes override methods in AWT classes. These methods are called when an event occurs. Each component gets most events, so it has to determine if it should handle the event. While this mechanism still can be used, it should be avoided.

The inheritance-base event model was too slow and did not provide the control over events that applications needed. It is replaced with the delegation event model. This model uses listeners. Components register for events that they are interested in.

S-nov16 3mins, S-nov18 2mins, Q-nov19 3mins Doc 24, JFC Basics Slide # 10

Delegation Event Model

AWT items generate events (mouse down, mouse moved) that other AWT items must respond to.

AWT items that must respond to events, need to "listen" the items that generate the events

Event objects are created and sent to AWT listeners. The event objects contain information about the "event" that triggered the generation of the event object.

S-nov18 46secs, Q-nov19 1min Doc 24, JFC Basics Slide # 11

Invoked when a window is activated.

Invoked when a window has been closed.

Invoked when a window is in the process of being closed.

Invoked when a window is de-activated.

Invoked when a window is de-iconified.

Invoked when a window is iconified.

Invoked when a window has been opened.

Doc 24, JFC Basics Slide # 12

Returns the window where this event originated.

Returns the component where this event originated.

Returns the event type.

The window activated event type.

The window closed event type.

The window closing event type.

The window deactivated event type.

The window deiconified event type.

Marks the first integer id for the range of window event ids.

The window iconified event type.

Marks the last integer id for the range of window event ids.

The window opened event type.

S-nov18 9mins, Q-nov19 6mins Doc 24, JFC Basics Slide # 13

Window Event Example

import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.awt.Frame;
import java.awt.Label;
class QuitableApplication1 extends  Frame 
   {
   public QuitableApplication1( int left, int top, int width, int height, String title )
      {
      super( title );
      setSize( width, height );
      setLocation( left, top);
      Label hello = new Label( "Hello World", Label.CENTER);
      add( hello, BorderLayout.CENTER  );
      addWindowListener( new QuitWindow( this ) );
      show();
      }
   }
class QuitWindow implements WindowListener
   {
   Frame myWindow;
   public QuitWindow( Frame aWindow )
      {
      myWindow = aWindow;
      }
   public void windowClosing(WindowEvent event) 
      {
      myWindow.dispose();
      System.exit(0);
      }
      
   public void windowActivated(WindowEvent event) {};
   public void windowClosed(WindowEvent event) {};
   public void windowDeactivated(WindowEvent event) {};
   public void windowDeiconified(WindowEvent event) {};
   public void windowIconified(WindowEvent event) {};
   public void windowOpened(WindowEvent event) {};
   }
S-nov18 4mins, Q-nov19 2mins Doc 24, JFC Basics Slide # 14

import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.awt.Frame;
import java.awt.Label;
class QuitableApplication2 extends  Frame 
   {
   public QuitableApplication2( int left, int top, int width, int height, String title )
      {
      super( title );
      setSize( width, height );
      setLocation( left, top);
      Label hello = new Label( "Hello World", Label.CENTER);
      add( hello, BorderLayout.CENTER  );
      addWindowListener( new QuitWindowAdapter( this ) );
      show();
      }
   }
class QuitWindowAdapter extends WindowAdapter
   {
   Frame myWindow;
   
   public QuitWindowAdapter( Frame aWindow )
      {
      myWindow = aWindow;
      }
      
   public void windowClosing( WindowEvent event )
      {
      myWindow.dispose();
      System.exit(0);
      }
   }
S-nov18 4mins, Q-nov19 3mins Doc 24, JFC Basics Slide # 15

import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.awt.Frame;
import java.awt.Label;
class QuitableApplication3 extends  Frame 
   {
   public QuitableApplication3( int left, int top, int width, int height, String title )
      {
      super( title );
      setSize( width, height );
      setLocation( left, top);
      Label hello = new Label( "Hello World", Label.CENTER);
      add( hello, BorderLayout.CENTER  );
      addWindowListener( new WindowAdapter( ) {
               public void windowClosing( WindowEvent event )
                  {
                  dispose();
                  System.exit(0);
                  }
               }
             );
      show();
      }
   }
S-nov18 4mins, Q-nov19 3mins Doc 24, JFC Basics Slide # 16

import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.awt.Frame;
import java.awt.Label;
class QuitableApplication4 extends  Frame 
   {
   public QuitableApplication4( int left, int top, int width, int height, String title )
      {
      super( title );
      setSize( width, height );
      setLocation( left, top);
      Label hello = new Label( "Hello World", Label.CENTER);
      add( hello, BorderLayout.CENTER );
      addWindowListener( new WindowAdapter( ) {
               public void windowClosing( WindowEvent event )
                  {
                  quit();
                  }
               }
             );
      show();
      }
   public void quit() 
      {
      dispose();
      System.exit( 0 );
      }
   }
S-nov18 53secs, Q-nov19 43secs Doc 24, JFC Basics Slide # 17

Overview of AWT Parts

When a user activates one of these controls -- by clicking a button for example -- it posts generates an event.

Ways of Getting User Input

S-nov18 1min, Q-nov19 1min Doc 24, JFC Basics Slide # 18

S-nov18 2mins, Q-nov19 46secs Doc 24, JFC Basics Slide # 19

Dialog, FileDialog, and Frame are subclasses of Window

Provide windows to contain components

Group components within an area of an existing window

S-nov18 3mins Doc 24, JFC Basics Slide # 20

S-nov18 5mins, Q-nov19 4mins Doc 24, JFC Basics Slide # 21

BorderLayout

CardLayout

FlowLayout

GridBagLayout

GridLayout

S-nov18 7mins, S-nov18b 9mins, Q-nov19 6mins Doc 24, JFC Basics Slide # 22

Button Examples

import java.awt.*;
class  FlowLayoutExample  extends Frame  {
   
   public FlowLayoutExample( int  width, int height ) {
      setTitle( "Flow Example" );
      setSize( width, height );
      setLayout( new FlowLayout( FlowLayout.LEFT) );
      
      for ( int label = 1; label < 10; label++ )
         add( new Button( String.valueOf( label ) ) );
      show();
   }
   public  static  void  main( String  args[] ) {
      new  FlowLayoutExample( 175, 100 );
   }
}

S-nov18b 9mins, Q-nov19 8mins Doc 24, JFC Basics Slide # 23

import java.awt.*;

class  BorderLayoutExample  extends Frame  {
   
   public BorderLayoutExample( int  widthInPixels, 
                           int heightInPixels ) {
      setTitle( "BorderLayout Example" );
      setSize( widthInPixels, heightInPixels );
      setLayout( new BorderLayout() );
      
      add( new Button( "North" ), BorderLayout.NORTH );
      add(  new Button( "Center" ), BorderLayout.CENTER );
      add(  new Button( "East" ), BorderLayout.EAST );
      add(  new Button( "West" ), BorderLayout.WEST );
      add(  new Button( "South" ), BorderLayout.SOUTH );
      show();
   }
   
   public  static  void  main( String  args[] ) {
      new  BorderLayoutExample( 175, 100 );
   }
}

S-nov18b 9mins, Q-nov19 4mins Doc 24, JFC Basics Slide # 24

Button Events

import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
class  ButtonExample  extends Frame {
   Button red = new Button( "Red" );
   Button blue = new Button( "Blue" );
   
   public ButtonExample( int  widthInPixels, int heightInPixels ) {
      setTitle( "Button Example" );
      setSize( widthInPixels, heightInPixels );
      setLayout( new FlowLayout() );
      add( red );
      add( blue );
      
      red.addActionListener( new ColorActionListener( Color.red) );
      blue.addActionListener( new ColorActionListener( Color.blue) );
      show();
   }
   public  static  void  main( String  args[] ){
      ButtonExample  window = new  ButtonExample(200, 50);
      }
   
   class ColorActionListener implements ActionListener {
      Color backgroundColor;
      
      public ColorActionListener( Color aColor ) {
         backgroundColor = aColor;
      }
      
      public void actionPerformed( ActionEvent event )  {
         setBackground( backgroundColor );
         repaint();      // Show effect of color change
      }
   }
}

S-nov18b 3mins, Q-nov19 33secs Doc 24, JFC Basics Slide # 25

import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
class  ActionEventDataExample  extends Frame
   {
   Button left = new Button( "Left" );
   Button right = new Button( "Right" );
   
   public ActionEventDataExample( int  widthInPixels, int heightInPixels )
      {
      setTitle( "Button Example" );
      setSize( widthInPixels, heightInPixels );
      setLayout( new FlowLayout() );
      add( left );
      add( right );
      
      left.addActionListener( new ActionData( ) );
      right.addActionListener( new ActionData( ) );
      show();
      }
            
   public  static  void  main( String  args[] ){
      ActionEventDataExample  window = 
         new  ActionEventDataExample(200, 50);
      }
Q-nov19 9mins Doc 24, JFC Basics Slide # 26

   class ActionData implements ActionListener
      {
      public void actionPerformed( ActionEvent event ) 
         {
         String command = event.getActionCommand();
         int modifiers = event.getModifiers();
         String parameters = event.paramString();
         System.out.println( "Command " + command);
         System.out.println( "Parameters " + parameters);
         
         switch ( modifiers )
            {
            case ActionEvent.ALT_MASK: 
               System.out.println( "Alt Key was pressed");
               break;
            case ActionEvent.CTRL_MASK: 
               System.out.println( "Control Key was pressed");
               break;
            case ActionEvent.META_MASK: 
               System.out.println( "Meta Key was pressed");
               break;
            case ActionEvent.SHIFT_MASK: 
               System.out.println( "Shift Key was pressed");
               break;
            default:
               System.out.println( "No modifier keys were pressed");
            }
         }
      }
   }

S-nov23 3mins Doc 24, JFC Basics Slide # 27

import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
class BadExample extends Frame
   {
   Button red = new Button( "Red" );
   Button blue = new Button( "Blue" );
   
   public BadExample( int  widthInPixels, int heightInPixels )
      {
      setTitle( "Button Example" );
      setSize( widthInPixels, heightInPixels );
      setLayout( new FlowLayout() );
      add( red );
      add( blue );
      
      red.addActionListener( new BadColorActionListener( ) );
      blue.addActionListener( new BadColorActionListener( ) );
      show();
      }
   public  static  void  main( String  args[] ){
      BadExample  window = new  BadExample(200, 50);
      }
   
   class BadColorActionListener implements ActionListener
      {
      public void actionPerformed( ActionEvent event ) 
         {
         String button = event.getActionCommand();
         if ( button.equals( "Red" ) )
            setBackground( Color.red );
         else if ( button.equals( "Blue" ) )
            setBackground( Color.blue );
         repaint();      // Show effect of color change
         }
      }
   }
S-nov23 2mins Doc 24, JFC Basics Slide # 28

import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
class CountButton extends Button implements ActionListener {
   int count = 0;
   
   public CountButton() {
      super( "0" );
      addActionListener( this );
   }
   
   public void actionPerformed( ActionEvent event )  {
      if (event.getSource() == this ) {
         count++;
         setLabel( String.valueOf( count ) );
      }
   }
}
class  SpecialButtonExample  extends Frame {
   public SpecialButtonExample( int  widthInPixels, int heightInPixels ) {
      setTitle( "Button Example" );
      setSize( widthInPixels, heightInPixels );
      setLayout( new FlowLayout() );
      add( new CountButton() );
      
      show();
   }
            
   public  static  void  main( String  args[] ){
      SpecialButtonExample  window = new  SpecialButtonExample(200, 50);
   }
}

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