org.jcsp.awt
Class ActiveCheckboxMenuItem

java.lang.Object
  java.awt.MenuComponent
      java.awt.MenuItem
          java.awt.CheckboxMenuItem
              org.jcsp.awt.ActiveCheckboxMenuItem

All Implemented Interfaces:

ItemSelectable, Serializable, Accessible, CSProcess

public class ActiveCheckboxMenuItem
extends CheckboxMenuItem
implements CSProcess

java.awt.CheckboxMenuItem with a channel interface.

Process Diagram

Description

ActiveCheckboxMenuItem is a process extension of java.awt.CheckboxMenuItem 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 ActiveCheckboxMenuItem is selected. 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 myCheckboxMenuItemEvent = Channel.one2one (new OverWriteOldestBuffer (n));
 
   final ActiveCheckboxMenuItem myCheckboxMenuItem =
     new ActiveCheckboxMenuItem (null, myCheckboxMenuItemEvent.out (), "Choose Me");
 

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 ActiveCheckboxMenuItem to the value of the String
	java.awt.MenuShortcut	Sets the MenuShortcut for the ActiveCheckboxMenuItem
	Boolean	If this is the Boolean.TRUE object, the checkboxMenuItem is made active If this is the Boolean.FALSE object, the checkboxMenuItem is made inactive Other Boolean objects are ignored
	ActiveCheckboxMenuItem.Configure	Invoke the user-defined Configure.configure method on the checkboxMenuItem.
Output Channels
event	java.awt.ItemEvent	The generated java.awt.ItemEvent is written down this channel (when the checkboxMenuItem is selected or deslected)
actionEvent	ActionEvent	See the addActionEventChannel method.

Example

 import java.awt.*;
 import java.awt.event.*;
 import org.jcsp.lang.*;
 import org.jcsp.util.*;
 import org.jcsp.awt.*;
 
 public class ActiveCheckboxMenuItemExample {
 
   public static void main (String argv[]) {
 
     final ActiveClosingFrame activeClosingFrame =
       new ActiveClosingFrame ("ActiveCheckboxMenuItem Example");
 
     final ActiveFrame frame = activeClosingFrame.getActiveFrame ();
 
     final MenuBar menuBar = new MenuBar ();
     frame.setMenuBar (menuBar);
 
     final Menu fileMenu = new Menu ("File");
     final Menu langMenu = new Menu ("Language");
     menuBar.add (fileMenu);
     menuBar.add (langMenu);
 
     final String[] fileOptions = {"Hello World", "Rocket Science", "CSP",
                                   "Monitors", "Ignore Me", "Goodbye World"};
     final String[] langOptions = {"occam-pi", "Java", "Smalltalk", "Algol-60",
                                   "Pascal", "Haskell", "SML", "Lisp"};
 
     final Any2OneChannel event[] = Channel.any2oneArray (2, new OverWriteOldestBuffer (10));
 
     final ActiveMenuItem[] fileMenuItem =
       new ActiveMenuItem[fileOptions.length];
     for (int i = 0; i < fileOptions.length; i++) {
       fileMenuItem[i] = new ActiveMenuItem (null, event[0].out (), fileOptions[i]);
       fileMenu.add (fileMenuItem[i]);
     }
 
     final ActiveCheckboxMenuItem[] langCheckboxMenuItem =
       new ActiveCheckboxMenuItem[langOptions.length];
     for (int i = 0; i < langOptions.length; i++) {
       langCheckboxMenuItem[i] =
         new ActiveCheckboxMenuItem (null, event[1].out (), langOptions[i]);
       langMenu.add (langCheckboxMenuItem[i]);
     }
 
     frame.setSize (300, 200);
     frame.setBackground (Color.green);
     frame.setVisible (true);
 
     new Parallel (
       new CSProcess[] {
         activeClosingFrame,
         new Parallel (fileMenuItem),
         new Parallel (langCheckboxMenuItem),
         new CSProcess () {
           public void run () {
             boolean running = true;
             while (running) {
               final String s = (String) event[0].in ().read ();
               System.out.println ("File ==> `" + s + "' selected ...");
               running = (s != fileOptions[fileOptions.length - 1]);
             }
             frame.setVisible (false);
             System.exit (0);
           }
         },
         new CSProcess () {
           public void run () {
             while (true) {
               final ItemEvent e = (ItemEvent) event[1].in ().read ();
               final String item = (String) e.getItem ();
               System.out.print ("Language ==> `" + item);
               if (e.getStateChange () == ItemEvent.SELECTED) {
                 System.out.println ("' selected ...");
               } else {
                 System.out.println ("' deselected ...");
               }
             }
           }
         }
       }
     ).run ();
 
   }
 
 }
 

Author:

P.D. Austin and P.H. Welch

See Also:

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

Nested Class Summary

static interface

ActiveCheckboxMenuItem.Configure This enables general configuration of this component.

Nested classes/interfaces inherited from class java.awt.CheckboxMenuItem

CheckboxMenuItem.AccessibleAWTCheckboxMenuItem

Nested classes/interfaces inherited from class java.awt.MenuItem

MenuItem.AccessibleAWTMenuItem

Nested classes/interfaces inherited from class java.awt.MenuComponent

MenuComponent.AccessibleAWTMenuComponent

Constructor Summary

ActiveCheckboxMenuItem()
Constructs a new unchecked ActiveCheckboxMenuItem with no initial label and no configuration or event channels.

ActiveCheckboxMenuItem(ChannelInput configure, ChannelOutput event)
Constructs a new unchecked ActiveCheckboxMenuItem with no initial label.

ActiveCheckboxMenuItem(ChannelInput configure, ChannelOutput event, String s)
Constructs a new unchecked ActiveCheckboxMenuItem.

ActiveCheckboxMenuItem(ChannelInput configure, ChannelOutput event, String s, boolean state)
Constructs a new ActiveCheckboxMenuItem.

ActiveCheckboxMenuItem(String s)
Constructs a new unchecked ActiveCheckboxMenuItem with no configuration or event channels.

ActiveCheckboxMenuItem(String s, boolean state)
Constructs a new ActiveCheckboxMenuItem with no configuration or event channels.

Method Summary

void	addActionEventChannel(ChannelOutput actionEvent) Add a new channel to this component that will be used to notify that an ActionEvent has occurred.
void	run() The main body of this process.
void	setConfigureChannel(ChannelInput configure) Sets the configuration channel for this ActiveCheckboxMenuItem.

Methods inherited from class java.awt.CheckboxMenuItem

addItemListener, addNotify, getAccessibleContext, getItemListeners, getListeners, getSelectedObjects, getState, paramString, processEvent, processItemEvent, removeItemListener, setState

Methods inherited from class java.awt.MenuItem

addActionListener, deleteShortcut, disable, disableEvents, enable, enable, enableEvents, getActionCommand, getActionListeners, getLabel, getShortcut, isEnabled, processActionEvent, removeActionListener, setActionCommand, setEnabled, setLabel, setShortcut

Methods inherited from class java.awt.MenuComponent

dispatchEvent, getFont, getName, getParent, getPeer, getTreeLock, postEvent, removeNotify, setFont, setName, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

ActiveCheckboxMenuItem

public ActiveCheckboxMenuItem()

Constructs a new unchecked ActiveCheckboxMenuItem with no initial label and no configuration or event channels.

ActiveCheckboxMenuItem

public ActiveCheckboxMenuItem(String s)

Constructs a new unchecked ActiveCheckboxMenuItem with no configuration or event channels.

Parameters:

s - the initial label displayed on the checkboxMenuItem.

ActiveCheckboxMenuItem

public ActiveCheckboxMenuItem(String s,
                              boolean state)

Constructs a new ActiveCheckboxMenuItem with no configuration or event channels.

Parameters:

s - the initial label displayed on the checkboxMenuItem.

state - the initial state of the checkboxMenuItem.

ActiveCheckboxMenuItem

public ActiveCheckboxMenuItem(ChannelInput configure,
                              ChannelOutput event)

Constructs a new unchecked ActiveCheckboxMenuItem with no initial label.

Parameters:

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

event - the current label will be output when the checkboxMenuItem is selected -- can be null if no notification is required.

ActiveCheckboxMenuItem

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

Constructs a new unchecked ActiveCheckboxMenuItem.

Parameters:

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

event - the current label will be output when the checkboxMenuItem is selected -- can be null if no notification is required.

s - the initial label displayed on the checkboxMenuItem.

ActiveCheckboxMenuItem

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

Constructs a new ActiveCheckboxMenuItem.

Parameters:

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

event - the current label will be output when the checkboxMenuItem is selected -- can be null if no notification is required.

s - the initial label displayed on the checkboxMenuItem.

state - the initial state of the checkboxMenuItem.

Method Detail

setConfigureChannel

public void setConfigureChannel(ChannelInput configure)

Sets the configuration channel for this ActiveCheckboxMenuItem. 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.

addActionEventChannel

public void addActionEventChannel(ChannelOutput actionEvent)

Add a new channel to this component that will be used to notify that an ActionEvent has occurred. This should be used instead of registering a ActionListener 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:

actionEvent - the channel down which to send ActionEvents.

run

public void run()

The main body of this process.

Specified by:

run in interface CSProcess