jcsp.awt
Class ActiveCheckbox

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Checkbox
              |
              +--jcsp.awt.ActiveCheckbox

All Implemented Interfaces:

Accessible, CSProcess, ImageObserver, ItemSelectable, MenuContainer, Serializable

public class ActiveCheckbox

extends Checkbox

implements CSProcess

java.awt.Checkbox with a channel interface.

Process Diagram

                              __________________
                             |                  |
                             |                  | event
                             |                  |----->-----
                             |                  | (java.awt.event.ItemEvent)
                             |                  |
                             |                  | componentEvent 
                             |                  |----->-----
                             |                  | (java.awt.event.ComponentEvent)
                             |                  |
                             |                  | focusEvent 
                             |                  |----->-----
                   configure |                  | (java.awt.event.FocusEvent)
                  ----->-----|  ActiveCheckbox  |
          (java.lang.String) |                  | keyEvent 
         (java.lang.Boolean) |                  |----->-----
  (ActiveCheckbox.Configure) |                  | (java.awt.event.KeyEvent)
                             |                  |
                             |                  | mouseEvent 
                             |                  |----->-----
                             |                  | (java.awt.event.MouseEvent)
                             |                  |
                             |                  | mouseMotionEvent 
                             |                  |----->-----
                             |                  | (java.awt.event.MouseEvent)
                             |__________________|  
 

Description

ActiveCheckbox is a process extension of java.awt.Checkbox with channels for run-time configuration and event notification. The event channels should be connected to one or more application-specific server processes (instead of registering a passive object as a Listener to this component).

All channels are optional. The configure and event channels are settable from a constructor. The event channel delivers the generated java.awt.ItemEvent whenever the ActiveCheckbox is operated. Other event channels can be added to notify the occurrence of any other events the component generates (by calling the appropriate addXXXEventChannel method before the process is run). Messages can be sent down the configure channel at any time to configure the component. See the table below for details.

All channels are managed by independent internal handler processes. It is, therefore, safe for a serial application process both to service an event channel and configure the component -- no deadlock can occur.

IMPORTANT: it is essential that event channels from this process are always serviced -- otherwise the Java Event Thread will be blocked and the GUI will stop responding. A simple way to guarantee this is to use channels configured with overwriting buffers. For example:

   final One2OneChannel myCheckboxEvent =
     One2OneChannel.create (new OverWriteOldestBuffer (n));
 
   final ActiveCheckbox myCheckbox =
     new ActiveCheckbox (null, myCheckboxEvent);
 

This will ensure that the Java Event Thread will never be blocked. Slow or inattentive readers may miss rapidly generated events, but the n most recent events will always be available.

Channel Protocols

Input Channels
configure	String	Change the label for the ActiveCheckbox to the value of the String.
	Boolean	If this is the Boolean.TRUE object, the checkbox is made active If this is the Boolean.FALSE object, the checkbox is made inactive Other Boolean objects are used to set the on/off state of the checkbox
	ActiveCheckbox.Configure	Invoke the user-defined Configure.configure method on the checkbox.
Output Channels
event	ItemEvent	When the ActiveCheckbox is operated, the generated java.awt.ItemEvent is written down this channel.
componentEvent	ComponentEvent	See the addComponentEventChannel method.
focusEvent	FocusEvent	See the addFocusEventChannel method.
keyEvent	KeyEvent	See the addKeyEventChannel method.
mouseEvent	MouseEvent	See the addMouseEventChannel method.
mouseMotionEvent	MouseEvent	See the addMouseMotionEventChannel method.

Example

 import java.awt.*;
 import java.awt.event.*;
 import jcsp.lang.*;
 import jcsp.util.*;
 import jcsp.awt.*;
 
 public class ActiveCheckboxExample {
 
   public static void main (String argv[]) {
 
     final Frame root = new Frame ("ActiveCheckbox Example");
 
     final String[] box = {"Hello World", "Rocket Science", "CSP",
                           "Monitors", "Ignore Me", "Goodbye World"};
 
     final Channel event =
       Any2OneChannel.create (new OverWriteOldestBuffer (10));
 
     final ActiveCheckbox[] check = new ActiveCheckbox[box.length];
     for (int i = 0; i < box.length; i++) {
       check[i] = new ActiveCheckbox (null, event, box[i]);
     }
 
     root.setSize (300, 100);
     root.setLayout (new GridLayout (box.length, 1));
     for (int i = 0; i < box.length; i++) {
      root.add (check[i]);
     }
     root.setVisible (true);
 
     new Parallel (
       new CSProcess[] {
         new Parallel (check),
         new CSProcess () {
           public void run () {
             boolean running = true;
             while (running) {
               final ItemEvent e = (ItemEvent) event.read ();
               final String item = (String) e.getItem ();
               if (e.getStateChange () == ItemEvent.SELECTED) {
                 System.out.println ("Checked ==> `" + item + "'");
                 running = (item != box[box.length - 1]);
               } else {
                 System.out.println ("Unchecked ==> `" + item + "'");
               }
             }
             root.setVisible (false);
             System.exit (0);
           }
         }
       }
     ).run ();
 
   }
 
 }
 

Author:

P.D.Austin and P.H.Welch

See Also:

Checkbox, CheckboxGroup, ItemEvent, ComponentEvent, FocusEvent, KeyEvent, MouseEvent, OverWriteOldestBuffer, Serialized Form

Inner Class Summary

static interface

ActiveCheckbox.Configure This enables general configuration of this component.

Inner classes inherited from class java.awt.Checkbox

Checkbox.AccessibleAWTCheckbox

Inner classes inherited from class java.awt.Component

Component.AccessibleAWTComponent

Fields inherited from class java.awt.Component

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Fields inherited from interface java.awt.image.ImageObserver

ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH

Constructor Summary

ActiveCheckbox()
Constructs an ActiveCheckbox with no label, initial state false and no configuration or event channels.

ActiveCheckbox(ChannelInput configure, ChannelOutput event)
Constructs an ActiveCheckbox with no label, initial state false and configuration and event channels.

ActiveCheckbox(ChannelInput configure, ChannelOutput event, String s)
Constructs a ActiveCheckbox with the label s, initial state false and configuration and event channels.

ActiveCheckbox(ChannelInput configure, ChannelOutput event, String s, boolean state)
Constructs an ActiveCheckbox with the label s, initial state and configuration and event channels.

ActiveCheckbox(ChannelInput configure, ChannelOutput event, String s, boolean state, CheckboxGroup group)
Constructs an ActiveCheckbox in the CheckboxGroup group with the label s, initial state and configuration and event channels.

ActiveCheckbox(String s)
Constructs an ActiveCheckbox with the label s, initial state false and no configuration or event channels.

ActiveCheckbox(String s, boolean state)
Constructs an ActiveCheckbox with the label s, initial state and no configuration or event channels.

ActiveCheckbox(String s, boolean state, CheckboxGroup group)
Constructs an ActiveCheckbox in the CheckboxGroup group with the label s, initial state and no configuration or event channels.

Method Summary

void	addComponentEventChannel(ChannelOutput componentEvent) Add a new channel to this component that will be used to notify that a ComponentEvent has occurred.
void	addFocusEventChannel(ChannelOutput focusEvent) Add a new channel to this component that will be used to notify that a FocusEvent has occurred.
void	addKeyEventChannel(ChannelOutput keyEvent) Add a new channel to this component that will be used to notify that a KeyEvent has occurred.
void	addMouseEventChannel(ChannelOutput mouseEvent) Add a new channel to this component that will be used to notify that a MouseEvent has occurred.
void	addMouseMotionEventChannel(ChannelOutput mouseMotionEvent) Add a new channel to this component that will be used to notify that a MouseMotionEvent has occurred.
void	run() The main body of this process.
void	setConfigureChannel(ChannelInput configure) Sets the configuration channel for this ActiveCheckbox.

Methods inherited from class java.awt.Checkbox

addItemListener, addNotify, getAccessibleContext, getCheckboxGroup, getLabel, getListeners, getSelectedObjects, getState, paramString, processEvent, processItemEvent, removeItemListener, setCheckboxGroup, setLabel, setState

Methods inherited from class java.awt.Component

action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addPropertyChangeListener, addPropertyChangeListener, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, deliverEvent, disable, disableEvents, dispatchEvent, doLayout, enable, enable, enableEvents, enableInputMethods, firePropertyChange, getAlignmentX, getAlignmentY, getBackground, getBounds, getBounds, getColorModel, getComponentAt, getComponentAt, getComponentOrientation, getCursor, getDropTarget, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getInputContext, getInputMethodRequests, getLocale, getLocation, getLocation, getLocationOnScreen, getMaximumSize, getMinimumSize, getName, getParent, getPeer, getPreferredSize, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, invalidate, isDisplayable, isDoubleBuffered, isEnabled, isFocusTraversable, isLightweight, isOpaque, isShowing, isValid, isVisible, keyDown, keyUp, layout, list, list, list, list, list, locate, location, lostFocus, minimumSize, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paint, paintAll, postEvent, preferredSize, prepareImage, prepareImage, print, printAll, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, reshape, resize, resize, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setFont, setForeground, setLocale, setLocation, setLocation, setName, setSize, setSize, setVisible, show, show, size, toString, transferFocus, update, validate

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ActiveCheckbox

public ActiveCheckbox()

Constructs an ActiveCheckbox with no label, initial state false and no configuration or event channels.

ActiveCheckbox

public ActiveCheckbox(String s)

Constructs an ActiveCheckbox with the label s, initial state false and no configuration or event channels.

Parameters:

s - the label displayed on the ActiveCheckbox.

ActiveCheckbox

public ActiveCheckbox(String s,
                      boolean state)

Constructs an ActiveCheckbox with the label s, initial state and no configuration or event channels.

Parameters:

s - the label displayed on the ActiveCheckbox.

state - the initial state of the ActiveCheckbox (true => on, false => off).

ActiveCheckbox

public ActiveCheckbox(String s,
                      boolean state,
                      CheckboxGroup group)

Constructs an ActiveCheckbox in the CheckboxGroup group with the label s, initial state and no configuration or event channels.

Parameters:

s - the label displayed on the ActiveCheckbox.

state - the initial state of the ActiveCheckbox. (true => on, false => off)

group - the CheckboxGroup for the ActiveCheckbox.

ActiveCheckbox

public ActiveCheckbox(ChannelInput configure,
                      ChannelOutput event)

Constructs an ActiveCheckbox with no label, initial state false and configuration and event channels.

Parameters:

configure - the channel for configuration events -- can be null if no configuration is required.

event - the ItemEvent will be output when the choice is exercised -- can be null if no notification is required.

ActiveCheckbox

public ActiveCheckbox(ChannelInput configure,
                      ChannelOutput event,
                      String s)

Constructs a ActiveCheckbox with the label s, initial state false and configuration and event channels.

Parameters:

configure - the channel for configuration events -- can be null if no configuration is required.

event - the ItemEvent will be output when the choice is exercised -- can be null if no notification is required.

s - the label displayed on the ActiveCheckbox.

ActiveCheckbox

public ActiveCheckbox(ChannelInput configure,
                      ChannelOutput event,
                      String s,
                      boolean state)

Constructs an ActiveCheckbox with the label s, initial state and configuration and event channels.

Parameters:

configure - the channel for configuration events -- can be null if no configuration is required.

event - the ItemEvent will be output when the choice is exercised -- can be null if no notification is required.

s - the label displayed on the ActiveCheckbox.

state - the initial state of the ActiveCheckbox. (true => on, false => off)

ActiveCheckbox

public ActiveCheckbox(ChannelInput configure,
                      ChannelOutput event,
                      String s,
                      boolean state,
                      CheckboxGroup group)

Constructs an ActiveCheckbox in the CheckboxGroup group with the label s, initial state and configuration and event channels.

Parameters:

configure - the channel for configuration events -- can be null if no configuration is required.

event - the ItemEvent will be output when the choice is exercised -- can be null if no notification is required.

s - the label displayed on the ActiveCheckbox.

state - the initial state of the ActiveCheckbox. (true => on, false => off)

group - the CheckboxGroup for the ActiveCheckbox.

Method Detail

setConfigureChannel

public void setConfigureChannel(ChannelInput configure)

Sets the configuration channel for this ActiveCheckbox. This method overwrites any configuration channel set in the constructor.

Parameters:

configure - the channel for configuration events -- can be null if no configuration is required.

addComponentEventChannel

public void addComponentEventChannel(ChannelOutput componentEvent)

Add a new channel to this component that will be used to notify that a ComponentEvent has occurred. This should be used instead of registering a ComponentListener with the component. It is possible to add more than one channel by calling this method multiple times If the channel passed is null, no action will be taken.

NOTE: This method must be called before this process is run.

Parameters:

componentEvent - the channel down which to send ComponentEvents.

addFocusEventChannel

public void addFocusEventChannel(ChannelOutput focusEvent)

Add a new channel to this component that will be used to notify that a FocusEvent has occurred. This should be used instead of registering a FocusListener with the component. It is possible to add more than one channel by calling this method multiple times If the channel passed is null, no action will be taken.

NOTE: This method must be called before this process is run.

Parameters:

focusEvent - the channel down which to send FocusEvents.

addKeyEventChannel

public void addKeyEventChannel(ChannelOutput keyEvent)

Add a new channel to this component that will be used to notify that a KeyEvent has occurred. This should be used instead of registering a KeyListener with the component. It is possible to add more than one channel by calling this method multiple times If the channel passed is null, no action will be taken.

NOTE: This method must be called before this process is run.

Parameters:

keyEvent - the channel down which to send KeyEvents.

addMouseEventChannel

public void addMouseEventChannel(ChannelOutput mouseEvent)

Add a new channel to this component that will be used to notify that a MouseEvent has occurred. This should be used instead of registering a MouseListener with the component. It is possible to add more than one channel by calling this method multiple times If the channel passed is null, no action will be taken.

NOTE: This method must be called before this process is run.

Parameters:

mouseEvent - the channel down which to send MouseEvents.

addMouseMotionEventChannel

public void addMouseMotionEventChannel(ChannelOutput mouseMotionEvent)

Add a new channel to this component that will be used to notify that a MouseMotionEvent has occurred. This should be used instead of registering a MouseMotionListener with the component. It is possible to add more than one channel by calling this method multiple times If the channel passed is null, no action will be taken.

NOTE: This method must be called before this process is run.

Parameters:

mouseMotionEvent - the channel down which to send MouseMotionEvents.

run

public void run()

The main body of this process.

Specified by:

run in interface CSProcess