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Class jcsp.awt.ActiveButton

java.lang.Object
   |
   +----java.awt.Component
           |
           +----java.awt.Button
                   |
                   +----jcsp.awt.ActiveButton

public class ActiveButton
extends Button
implements CSProcess

Process Diagram

External View

             ________________
  configure |                | event
 ----->-----|  ActiveButton  |--->---
            |________________|

Internal View

             __________________________________________
            |  ____________      ____________________  |
  configure | |            |    |                    | | event
 ----->-------|  Configure |    | ActionEventHandler |----->---
            | |____________|    |____________________| |
            |                                          |
            |                             ActiveButton |
            |__________________________________________|

Description

An ActiveButton is a sub class of Button which uses Channels for event notification and configuration.

If the event Channel is not a null reference an new ActionEventHandler is created with the Channel and is registered as ActionListener with the ActiveButton and has its actionPerformed() method invoked when ActionEvents are generated. Any events generated when the ActionEventHandler is blocked writing to the event Channel are ignored so that the main Java Event Thread is not blocked. The output from the ActionEventHanlder is connected to the event Channel causing an Object to be sent down the Channel when the Button is pressed.

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

To configure the Button 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	Change the label on the Button to the value of the String
configure	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	String	The label on the ActiveButton

Example

 import java.awt.*;
 import jcsp.lang.*;
 import jcsp.awt.*;
 public class ButtonExample extends Frame {
   public ButtonExample() {
     super("Button Example");
     final Channel close = new One2OneChannel();
     ActiveButton b = new ActiveButton(null, close, "Close");
     add(b);
     setVisible(true);
     new Parallel(new CSProcess[] {
       b,
       new CSProcess() {
         public void run() {
           close.read();
           setVisible(false);
           System.exit(0);
         }
       }
     }).run();
   }
   public static void main(String argv[]) {
     new ButtonExample();
   }
 }

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

par: The Parallel construct containing the processes to be executed by this CSProcess.

ActiveButton(): Constructs a new Button with no label, no configuration Channel and no event Channel.
ActiveButton(ChannelInput, ChannelOutput): Constructs a new Button with no label, the configuration Channel configure and the event Channel event.
ActiveButton(ChannelInput, ChannelOutput, String): Constructs a new Button with the label s, the configuration Channel configure and the event Channel event.
ActiveButton(String): Constructs a new Button with the label s, no configuration Channel and no event Channel.

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.

par

 protected Parallel par

The Parallel construct containing the processes to be executed by this CSProcess.

ActiveButton

 public ActiveButton()

Constructs a new Button with no label, no configuration Channel and no event Channel.

ActiveButton

 public ActiveButton(String s)

Constructs a new Button with the label s, no configuration Channel and no event Channel.

Parameters:: s - The label displayed on the ActiveButton

ActiveButton

 public ActiveButton(ChannelInput configure,
                     ChannelOutput event)

Constructs a new Button with no label, 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.

ActiveButton

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

Constructs a new Button with the label s, 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.; s - The label displayed on the ActiveButton

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.