org.jcsp.awt
Class ActiveMenuItem

java.lang.Object
  java.awt.MenuComponent
      java.awt.MenuItem
          org.jcsp.awt.ActiveMenuItem

All Implemented Interfaces:

Serializable, Accessible, CSProcess

public class ActiveMenuItem
extends MenuItem
implements CSProcess

java.awt.MenuItem with a channel interface.

Process Diagram

Description

ActiveMenuItem is a process extension of java.awt.MenuItem with channels for run-time configuration and event notification. The event channel should be connected to an application-specific server process (instead of registering a passive object as a Listener to this component).

The configure and event channels are settable from a constructor. The event channel delivers the current label on the ActiveMenuItem whenever it is selected. 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 the event channel and configure the component -- no deadlock can occur.

IMPORTANT: it is essential that a (non-null) event channel from this process is 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 myMenuItemEvent = Channel.one2one (new OverWriteOldestBuffer (n));
 
   final ActiveMenuItem myMenuItem =
     new ActiveMenuItem (null, myMenuItemEvent.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 ActiveMenuItem to the value of the String
	java.awt.MenuShortcut	Sets the MenuShortcut for the ActiveMenuItem
	Boolean	If this is the Boolean.TRUE object, the menuItem is made active If this is the Boolean.FALSE object, the menuItem is made inactive Other Boolean objects are ignored
	ActiveMenuItem.Configure	Invoke the user-defined Configure.configure method on the menuItem.
Output Channels
event	String	The label on the ActiveMenuItem (when the item is selected)

Example

 import java.awt.*;
 import org.jcsp.lang.*;
 import org.jcsp.util.*;
 import org.jcsp.awt.*;
 
 public class ActiveMenuItemExample {
 
   public static void main (String argv[]) {
 
     final ActiveClosingFrame activeClosingFrame =
       new ActiveClosingFrame ("ActiveMenuItem 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 ActiveMenuItem[] langMenuItem = new ActiveMenuItem[langOptions.length];
     for (int i = 0; i < langOptions.length; i++) {
       langMenuItem[i] = new ActiveMenuItem (null, event[1].out (), langOptions[i]);
       langMenu.add (langMenuItem[i]);
     }
 
     frame.setSize (300, 200);
     frame.setBackground (Color.green);
     frame.setVisible (true);
 
     new Parallel (
       new CSProcess[] {
         activeClosingFrame,
         new Parallel (fileMenuItem),
         new Parallel (langMenuItem),
         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 String s = (String) event[1].in ().read ();
               System.out.println ("Language ==> `" + s + "' selected ...");
             }
           }
         }
       }
     ).run ();
 
   }
 
 }
 

Author:

P.D. Austin and P.H. Welch

See Also:

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

Nested Class Summary

static interface

ActiveMenuItem.Configure This enables general configuration of this component.

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

MenuItem.AccessibleAWTMenuItem

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

MenuComponent.AccessibleAWTMenuComponent

Constructor Summary

ActiveMenuItem()
Constructs a new ActiveMenuItem with no label and no shortcut and no configuration or event channels.

ActiveMenuItem(ChannelInput configure, ChannelOutput event)
Constructs a new ActiveMenuItem with no label and no shortcut.

ActiveMenuItem(ChannelInput configure, ChannelOutput event, String s)
Constructs a new ActiveMenuItem with no shortcut.

ActiveMenuItem(ChannelInput configure, ChannelOutput event, String s, MenuShortcut ms)
Constructs a new ActiveMenuItem.

ActiveMenuItem(String s)
Constructs a new ActiveMenuItem with no shortcut and no configuration or event channels.

ActiveMenuItem(String s, MenuShortcut ms)
Constructs a new ActiveMenuItem with no configuration or event channels.

Method Summary

void	run() The main body of this process.
void	setConfigureChannel(ChannelInput configure) Sets the configuration channel for this ActiveMenuItem.

Methods inherited from class java.awt.MenuItem

addActionListener, addNotify, deleteShortcut, disable, disableEvents, enable, enable, enableEvents, getAccessibleContext, getActionCommand, getActionListeners, getLabel, getListeners, getShortcut, isEnabled, paramString, processActionEvent, processEvent, 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

ActiveMenuItem

public ActiveMenuItem()

Constructs a new ActiveMenuItem with no label and no shortcut and no configuration or event channels.

ActiveMenuItem

public ActiveMenuItem(String s)

Constructs a new ActiveMenuItem with no shortcut and no configuration or event channels.

Parameters:

s - the initial label displayed on the menuItem.

ActiveMenuItem

public ActiveMenuItem(String s,
                      MenuShortcut ms)

Constructs a new ActiveMenuItem with no configuration or event channels.

Parameters:

s - the initial label displayed on the menuItem.

ms - the MenuShortcut for the menuItem.

ActiveMenuItem

public ActiveMenuItem(ChannelInput configure,
                      ChannelOutput event)

Constructs a new ActiveMenuItem with no label and no shortcut.

Parameters:

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

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

ActiveMenuItem

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

Constructs a new ActiveMenuItem with no shortcut.

Parameters:

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

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

s - the initial label displayed on the menuItem.

ActiveMenuItem

public ActiveMenuItem(ChannelInput configure,
                      ChannelOutput event,
                      String s,
                      MenuShortcut ms)

Constructs a new ActiveMenuItem.

Parameters:

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

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

s - the initial label displayed on the menuItem.

ms - the MenuShortcut for the menuItem.

Method Detail

setConfigureChannel

public void setConfigureChannel(ChannelInput configure)

Sets the configuration channel for this ActiveMenuItem. 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.

run

public void run()

The main body of this process.

Specified by:

run in interface CSProcess