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Class jcsp.awt.ActiveList

java.lang.Object
   |
   +----java.awt.Component
           |
           +----java.awt.List
                   |
                   +----jcsp.awt.ActiveList

public class ActiveList
extends List
implements CSProcess

Process Diagram

External View

             ____________
  configure |            | event
 ----->-----| ActiveList |--->---
            |____________|

Internal View

             ________________________________________
            |  ____________      __________________  |
  configure | |            |    |                  | | event
 ----->-------|  Configure |    | ItemEventHandler |----->---
            | |____________|    |__________________| |
            |                                        |
            |                             ActiveList |
            |________________________________________|

Description

An ActiveList is a sub class of List which uses Channels for event notification and configuration.

If the event Channel is not a null reference an new ItemEventHandler is created with the Channel and registered as ItemListener with the ActiveList and has its itemStateChanged() method invoked when ItemEvents are generated. Any events generated when the ItemEventHandler is blocked writing to the event Channel are ignored so that the main Java Event Thread is not blocked. The output from the ItemEventHanlder is connected to the event Channel causing an Object to be sent down the Channel when the List is selected.

NOTE: As the component generates two Objects for each event the event Channel must be a One2OneChannel.

It is also possible to register Channels to be used to notify the occurrence of other types of Event that the List generates. This can be done by calling one of the addXXXXEventChannel() methods.

To configure the List messages can be sent down the configure channel. If the configure Channel is not a null reference a new Configure is created. The configure process sits in an infinite loop which reads from the configure Channel and configures the component based on the Object received (see table below for details).

Channel Protocols

Input Channels
configure	String	Sets the selected item in this List menu to be the item whose name is equal to the specified string. If more than one item matches (is equal to) the specified string, the one with the smallest index is selected.
	Integer	Sets the selected item in this List menu to be the item at the specified position.
	Boolean	If the Boolean Object refers to the Boolean.TRUE instance the button is made active If the Boolean Object refers to the Boolean.FALSE instance the button is made inactive If the Boolean Object refers to any other Boolean instance the message is discarded
Output Channels
event	Boolean followed by Integer	This component sends two Objects for each event. The first is a Boolean which will be true if the event was for selection false if it was for deselection. The second is an Integer representing the item that changed.

Example

 import java.awt.*;
 import jcsp.lang.*;
 import jcsp.awt.*;
 public class ListExample extends Frame {
   public ListExample() {
     super("List Example");
     final Channel close = new One2OneChannel();
     ActiveList c = new ActiveList(null, close);
     c.add("Ignore Me");
     c.add("Close Window");
     add(c);
     setVisible(true);
     new Parallel(new CSProcess[] {
       c,
       new CSProcess() {
         public void run() {
           close.read();
           Integer i = (Integer)close.read();
           if (i.intValue() == 1) {
             setVisible(false);
             System.exit(0);
           }
         }
       }
     }).run();
   }
   public static void main(String argv[]) {
     new ListExample();
   }
 }

Author:: P.D.Austin
See Also:: ItemEventHandler

ActiveList(): Constructs a List with no configuration Channel and no event Channel.
ActiveList(ChannelInput, ChannelOutput): Constructs a List with the configuration Channel configure and the event Channel event.
ActiveList(ChannelInput, ChannelOutput, int): Constructs a List with the configuration Channel configure and the event Channel event with the specified number of visible lines.
ActiveList(ChannelInput, ChannelOutput, int, boolean): Constructs a List with the configuration Channel configure and the event Channel event with the specified number of visible lines.
ActiveList(int): Constructs a List with no configuration Channel and no event Channel with the specified number of visible lines.
ActiveList(int, boolean): Constructs a List with no configuration Channel and no event Channel with the specified number of visible lines.

addComponentEventChannel(ChannelOutput): Add a new Channel to the Component which will be used to notify that a ComponentEvent has occurred on the component.
addFocusEventChannel(ChannelOutput): Add a new Channel to the Component which will be used to notify that a FocusEvent has occurred on the component.
addKeyEventChannel(ChannelOutput): Add a new Channel to the Component which will be used to notify that a KeyEvent has occurred on the component.
addMouseEventChannel(ChannelOutput): Add a new Channel to the Component which will be used to notify that a MouseEvent has occurred on the component.
addMouseMotionEventChannel(ChannelOutput): Add a new Channel to the Component which will be used to notify that a MouseMotionEvent has occurred on the component.
run(): The main body of this process.

ActiveList

 public ActiveList()

Constructs a List with no configuration Channel and no event Channel.

ActiveList

 public ActiveList(int rows)

Constructs a List with no configuration Channel and no event Channel with the specified number of visible lines.

Parameters:: rows - the number of items to show.

ActiveList

 public ActiveList(int rows,
                   boolean multipleMode)

Constructs a List with no configuration Channel and no event Channel with the specified number of visible lines. If the value of multipleMode is true, then the user can select multiple items from the list. If it is false, only one item at a time can be selected.

Parameters:: rows - the number of items to show.; multipleMode - if true, then multiple selections are allowed; otherwise, only one item can be selected at a time.

ActiveList

 public ActiveList(ChannelInput configure,
                   ChannelOutput event)

Constructs a List with the configuration Channel configure and the event Channel event.

Parameters:: configure - The Channel configuration events should be sent down. Can be null if no configuration is required.; event - The Channel events will be notified down when the button is pressed. Can be null if events are going to be ignored.

ActiveList

 public ActiveList(ChannelInput configure,
                   ChannelOutput event,
                   int rows)

Constructs a List with the configuration Channel configure and the event Channel event with the specified number of visible lines.

Parameters:: configure - The Channel configuration events should be sent down. Can be null if no configuration is required.; event - The Channel events will be notified down when the button is pressed. Can be null if events are going to be ignored.; rows - the number of items to show.

ActiveList

 public ActiveList(ChannelInput configure,
                   ChannelOutput event,
                   int rows,
                   boolean multipleMode)

Constructs a List with the configuration Channel configure and the event Channel event with the specified number of visible lines. If the value of multipleMode is true, then the user can select multiple items from the list. If it is false, only one item at a time can be selected.

Parameters:: configure - The Channel configuration events should be sent down. Can be null if no configuration is required.; event - The Channel events will be notified down when the button is pressed. Can be null if events are going to be ignored.; rows - the number of items to show.; multipleMode - if true, then multiple selections are allowed; otherwise, only one item can be selected at a time.

addComponentEventChannel

 public void addComponentEventChannel(ChannelOutput componentEvent)

Add a new Channel to the Component which will be used to notify that a ComponentEvent has occurred on the component. 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 reference passed is null no action will be taken. Otherwise a new ComponentEventHanlder will be generated for the Channel so that each Channel operates independently of the others.