jcsp.awt
Class ActiveLabel

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Label
              |
              +--jcsp.awt.ActiveLabel

All Implemented Interfaces:

Accessible, CSProcess, ImageObserver, MenuContainer, Serializable

public class ActiveLabel

extends Label

implements CSProcess

java.awt.Label with a channel interface.

Process Diagram

                           _________________
                          |                 |
                          |                 | componentEvent
                          |                 |----->-----
                          |                 | (java.awt.event.ComponentEvent)
                          |                 |
                          |                 | focusEvent
                          |                 |----->-----
                          |                 | (java.awt.event.FocusEvent)
                          |                 |
                configure |                 | keyEvent
               ----->-----|   ActiveLabel   |----->-----
  (ActiveLabel.Configure) |                 | (java.awt.event.KeyEvent)
                          |                 |
                          |                 | mouseEvent
                          |                 |----->-----
                          |                 | (java.awt.event.MouseEvent)
                          |                 |
                          |                 | mouseMotionEvent
                          |                 |----->-----
                          |                 | (java.awt.event.MouseEvent)
                          |_________________|  
 

Description

ActiveLabel is a process extension of java.awt.Label 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 channel is settable from a constructor. Event channels can be added to notify the occurrence of any type of Event 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 myMouseEvent =
     One2OneChannel.create (new OverWriteOldestBuffer (n));
 
   final ActiveLabel myLabel = new ActiveLabel ("Look at Me");
   myContainer.addMouseEventChannel (myMouseEvent);
 

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 on the ActiveLabel to the value of the String
	Boolean	If this is the Boolean.TRUE object, the label is made active If this is the Boolean.FALSE object, the label is made inactive Other Boolean objects are ignored
	ActiveLabel.Configure	Invoke the user-defined Configure.configure method on the label.
Output Channels
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 jcsp.lang.*;
 import jcsp.util.*;
 import jcsp.awt.*;
 
 public class ActiveLabelExample {
 
   public static void main (String argv[]) {
 
     final Frame root = new Frame ("ActiveLabel Example");
 
     final int nLabels = 8;
     final int countdown = 10;
 
     final One2OneChannel[] configureLabel = One2OneChannel.create (nLabels);
 
     final ActiveLabel[] label = new ActiveLabel[nLabels];
     for (int i = 0; i < label.length; i++) {
       label[i] = new ActiveLabel (configureLabel[i], "==>  " + countdown + "  <==");
       label[i].setAlignment (Label.CENTER);
     }
 
     final One2OneChannel configureButton = new One2OneChannel ();
     final One2OneChannel event = One2OneChannel.create (new OverWriteOldestBuffer (10));
 
     final ActiveButton button = new ActiveButton (configureButton, event, "Start");
 
     root.setSize (300, 200);
     root.setLayout (new GridLayout (3, 3));
     for (int i = 0; i < nLabels + 1; i++) {
       if (i < 4) {
         root.add (label[i]);
       } else if (i == 4) {
         root.add (button);
       } else if (i > 4) {
         root.add (label[i - 1]);
       }
     }
     root.setVisible (true);
 
     new Parallel (
       new CSProcess[] {
         new Parallel (label),
         button,
         new CSProcess () {
           public void run () {
             final long second = 1000;
             CSTimer tim = new CSTimer ();
             Alternative alt = new Alternative (new Guard[] {event, tim});
             event.read ();              // wait for the start signal
             configureButton.write ("Restart");
             int count = countdown;
             long timeout = tim.read () + second;
             while (count > 0) {
               tim.setAlarm (timeout);
               switch (alt.priSelect ()) {
                 case 0:                 // reset signal
                   event.read ();        // clear the reset
                   timeout = tim.read () + second;
                   count = countdown;
                 break;
                 case 1:                 // timeout signal
                   timeout += second;
                   count--;
                 break;
               }
               final String newLabel = "==>  " + count + "  <==";
               for (int i = 0; i < nLabels; i++) {
                 configureLabel[i].write (newLabel);
               }
             }
             root.setVisible (false);
             System.exit (0);
           }
         }
       }
     ).run ();
 
   }
 
 }
 

Author:

P.D.Austin and P.H.Welch

See Also:

Label, ComponentEvent, FocusEvent, KeyEvent, MouseEvent, OverWriteOldestBuffer, Serialized Form

Inner Class Summary

static interface

ActiveLabel.Configure This enables general configuration of this component.

Inner classes inherited from class java.awt.Label

Label.AccessibleAWTLabel

Inner classes inherited from class java.awt.Component

Component.AccessibleAWTComponent

Fields inherited from class java.awt.Label

CENTER, LEFT, RIGHT

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

ActiveLabel()
Constructs a new ActiveLabel with no label or configuration channel.

ActiveLabel(ChannelInput configure)
Constructs a new ActiveLabel with no initial label.

ActiveLabel(ChannelInput configure, String s)
Constructs a new ActiveLabel.

ActiveLabel(String s)
Constructs a new ActiveLabel with no configuration channel.

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 ActiveLabel.

Methods inherited from class java.awt.Label

addNotify, getAccessibleContext, getAlignment, getText, paramString, setAlignment, setText

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, getListeners, 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, processEvent, 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

ActiveLabel

public ActiveLabel()

Constructs a new ActiveLabel with no label or configuration channel.

ActiveLabel

public ActiveLabel(String s)

Constructs a new ActiveLabel with no configuration channel.

Parameters:

s - the initial string displayed on the label.

ActiveLabel

public ActiveLabel(ChannelInput configure)

Constructs a new ActiveLabel with no initial label.

Parameters:

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

ActiveLabel

public ActiveLabel(ChannelInput configure,
                   String s)

Constructs a new ActiveLabel.

Parameters:

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

s - the initial string displayed on the label.

Method Detail

setConfigureChannel

public void setConfigureChannel(ChannelInput configure)

Sets the configuration channel for this ActiveLabel. 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