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Class jcsp.awt.ActiveApplet

java.lang.Object
   |
   +----java.awt.Component
           |
           +----java.awt.Container
                   |
                   +----java.awt.Panel
                           |
                           +----java.applet.Applet
                                   |
                                   +----jcsp.awt.ActiveApplet

public abstract class ActiveApplet
extends Applet
implements CSProcess

Process Diagram

  ________________
 |                |
 |  ActiveApplet  |
 |________________|

Description

The ActiveApplet is a sub class of Applet which controls a ProcessNetwork of CSProcess's. A ProcessNetwork is created to execute the run() method of the ActiveApplet, this enables the ActiveApplet to suspend the CSProcess's created by the sub classes when the stop() method is invoked, resume them when start() is invoked and stop them when stop() is invoked.

NOTE: Unlike most other CSProcess's the ActiveApplet uses a ProcessNetwork to execute the run() method asynchronously, therefore the ActiveApplet does not need to be part of a Parallel construct.

A Parallel construct is constructed as a protected variable which is used to execute the CSProcess's defined by this class and by sub classes in parallel. The run method of this class simply sets the Parallel construct running and will not complete unless all the CSProcess's terminate. Applets sub classing this class should call par.addProcess() to add any CSProcess's they which to be executed.

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

When creating a new ActiveApplet the init() method should be overridden to define the components to be displayed and the CSProcess's to be executed. Finally the ProcessNetwork must be started using network.start().

NOTE: If network.start() is called before further calls to par.addProcess() the CSProcess's added after will not be executed.

Channel Protocols

Input Channels

Output Channels

Example

 import jcsp.lang.*;
 import jcsp.awt.*;
 public class AppletExample extends ActiveApplet {
   public void init() {
     setLayout(new FlowLayout());
     final Channel event = new One2OneChannel();
     final Channel label = new One2OneChannel();
     ActiveButton b = new ActiveButton(event, "Click Me");
     add(b);
     ActiveLabel l = new ActiveLabel(label)
     add(l);
     par.addProcess(new CSProcess[] {
       b,
       l,
       new CSProcess() {
         public void run() {
           int clickCount = 0;
           while (true) {
             event.read();
             label.write("Clicked " + clickCount " times");
           }
         }
       }
     });
     network.start(); // Must be called to start the processes running
   }
 }

Author:: P.D.Austin

network: The ProcessNetwork used to control the execution of this CSProcess.
par: The Parallel construct containing the processes to be executed by this CSProcess.

ActiveApplet(): Called when the Applet is first initialised, this method will create a new ProcessNetwork to run this process in.

addComponentEventChannel(ChannelOutput): Add a new Channel to the Component which will be used to notify that a ComponentEvent has occurred on the component.
addContainerEventChannel(ChannelOutput): Add a new Channel to the Container which will be used to notify that a ContainerEvent has occurred on the Container.
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.
destroy(): Called when the Applet needs to be destroyed.
run(): The main body of this process.
start(): Called when the Applet is made visible.
stop(): Called when the Applet is made not visible.

par

 protected Parallel par

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

network

 protected ProcessNetwork network

The ProcessNetwork used to control the execution of this CSProcess.

ActiveApplet

 public ActiveApplet()

Called when the Applet is first initialised, this method will create a new ProcessNetwork to run this process in. This method will wait to be notified by the run() process. Sub classes should not override this method and must call notify in the run() method when the process network has been created, but before the infinite loop is created.

NOTE: If subclasses override this method they must call super.init().

destroy

 public void destroy()

Called when the Applet needs to be destroyed. This method will stop the ProcessNetwork causing all the CSProcess's to stop.

NOTE: If subclasses override this method they must call super.destory().

Overrides:: destroy in class Applet

start

 public void start()

Called when the Applet is made visible. This method will resume the ProcessNetwork causing all the CSProcess's to resume execution.

NOTE: If subclasses override this method they must call super.start().

Overrides:: start in class Applet

stop

 public void stop()

Called when the Applet is made not visible. This method will suspend the ProcessNetwork causing all the CSProcess's to suspend execution.

NOTE: If subclasses override this method they must call super.stop().

Overrides:: stop in class Applet

addContainerEventChannel

 public void addContainerEventChannel(ChannelOutput containerEvent)

Add a new Channel to the Container which will be used to notify that a ContainerEvent has occurred on the Container. This should be used instead of registering a ContainerListener with the Container. 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 ContainerEventHanlder will be generated for the Channel so that each Channel operates independently of the others.