org.jcsp.awt
Class ActiveTextEnterField

java.lang.Object
  org.jcsp.awt.ActiveTextEnterField

All Implemented Interfaces:

CSProcess

public class ActiveTextEnterField
extends Object
implements CSProcess

A specialisation of ActiveTextField that writes text to the event channel only when ENTER or ESCAPE is pressed.

Process Diagram

Description

ActiveTextEnterField is a process containing an ActiveTextField, configured with channels for event notification and configuration. 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 difference between this class and ActiveTextField is that text is only written to the event channel when ENTER or ESCAPE is pressed on the text field (not on every keystroke). When this happens, the text field is temporarilly disabled for (by default) half a second; this is to give feedback to the user. The disable period can be changed by calling the setDisableTime method before the process is run.

The internal ActiveTextField can be extracted with the getActiveTextField method. Channels can then be added to notify the occurrence of any other type of Event the ActiveFrame generates. This is done by calling its appropriate addXXXEventChannel method (before the process is run). As many channels can be added as are needed.

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 the output channels from this process are always serviced -- otherwise the Java Event Thread will be blocked and the GUI will stop responding. The simplest way to guarantee this is to use channels configured with overwriting buffers. For example:

   final One2OneChannel myTextFieldEvent = Channel.one2one (new OverWriteOldestBuffer (n));
 
   final ActiveTextEnterField myTextEnterField =
     new ActiveTextEnterField (null, myTextFieldEvent.out (), "Edit 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	Set the text in this ActiveTextEnterField to the value of the String
	Boolean	If this is the Boolean.TRUE object, the text field is made active If this is the Boolean.FALSE object, the text field is made inactive Other Boolean objects are ignored
	ActiveTextField.Configure	Invoke the user-defined Configure.configure method on the textField.
	otherwise	Append the toString form of the object to the text in this ActiveTextField.
Output Channels
event	String	The text in the ActiveTextEnterField (whenever ENTER or ESCAPE is pressed)
componentEvent	ComponentEvent	See the getActiveTextField.addComponentEventChannel method.
focusEvent	FocusEvent	See the getActiveTextField.addFocusEventChannel method.
keyEvent	KeyEvent	See the getActiveTextField.addKeyEventChannel method.
mouseEvent	MouseEvent	See the getActiveTextField.addMouseEventChannel method.
mouseMotionEvent	MouseEvent	See the getActiveTextField.addMouseMotionEventChannel method.

Example

 import org.jcsp.lang.*;
 import org.jcsp.util.*;
 import org.jcsp.awt.*;
 import java.awt.*;
 
 public class ActiveTextEnterFieldExample {
 
   public static void main (String argv[]) {
 
     final ActiveClosingFrame frame =
       new ActiveClosingFrame ("ActiveTextEnterField Example");
 
     final Any2OneChannel event = Channel.any2one (new OverWriteOldestBuffer (10));
 
     final String[] string =
       {"Entia Non Sunt Multiplicanda Praeter Necessitatem",
        "Less is More ... More or Less",
        "Everything we do, we do it to you",
        "Race Hazards - What Rice Hozzers?",
        "Cogito Ergo Occam"};
 
     final String goodbye = "Goodbye World";
 
     final ActiveTextEnterField[] activeText =
       new ActiveTextEnterField[string.length];
 
     for (int i = 0; i < string.length; i++) {
       activeText[i] = new ActiveTextEnterField (null, event.out (), string[i]);
     }
 
     Panel panel = new Panel (new GridLayout (string.length, 1));
     for (int i = 0; i < string.length; i++) {
       panel.add (activeText[i].getActiveTextField ());
     }
 
     final Frame realFrame = frame.getActiveFrame ();
     realFrame.setBackground (Color.green);
     realFrame.add (panel);
     realFrame.pack ();
     realFrame.setVisible (true);
 
     new Parallel (
       new CSProcess[] {
         frame,
         new Parallel (activeText),
         new CSProcess () {
           public void run () {
             boolean running = true;
             while (running) {
               String s = (String) event.in ().read ();
               System.out.println (s);
               running = (! s.equals (goodbye));
             }
             realFrame.setVisible (false);
             System.exit (0);
           }
         }
       }
     ).run ();
   }
 
 }
 

Author:

P.D. Austin and P.H. Welch

See Also:

ActiveTextField, TextField, ComponentEvent, FocusEvent, KeyEvent, MouseEvent, OverWriteOldestBuffer

Constructor Summary

ActiveTextEnterField(AltingChannelInput configure, ChannelOutput event)
Constructs a new ActiveTextEnterField with configuration and event channels, but no initial text.

ActiveTextEnterField(AltingChannelInput configure, ChannelOutput event, String s)
Constructs a new ActiveTextEnterField with configuration and event channels, initial text and default width.

ActiveTextEnterField(AltingChannelInput configure, ChannelOutput event, String s, int columns)
Constructs a new ActiveTextEnterField with configuration and event channels, initial text and width.

Method Summary

ActiveTextField	getActiveTextField() This is used to get the ActiveTextField within this component so that it can be configured (using TextField or ActiveTextField methods) or added to some container.
void	run() The main body of this process.
void	setConfigureChannel(AltingChannelInput configure) Sets the configuration channel for this ActiveTextEnterField.
void	setDisableTime(long disableTime) This is used to set the time during which the text field is disabled after an ENTER or ESCAPE has been entered.

Methods inherited from class java.lang.Object

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

Constructor Detail

ActiveTextEnterField

public ActiveTextEnterField(AltingChannelInput configure,
                            ChannelOutput event)

Constructs a new ActiveTextEnterField with configuration and event channels, but no initial text.

Parameters:

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

event - the current text will be output when the ENTER or ESCAPE key is pressed -- can be null if no notification is required.

ActiveTextEnterField

public ActiveTextEnterField(AltingChannelInput configure,
                            ChannelOutput event,
                            String s)

Constructs a new ActiveTextEnterField with configuration and event channels, initial text and default width.

Parameters:

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

event - the current text will be output when the ENTER or ESCAPE key is pressed -- can be null if no notification is required.

s - the initial text displayed in the field.

ActiveTextEnterField

public ActiveTextEnterField(AltingChannelInput configure,
                            ChannelOutput event,
                            String s,
                            int columns)

Constructs a new ActiveTextEnterField with configuration and event channels, initial text and width.

Parameters:

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

event - the current text will be output when the ENTER or ESCAPE key is pressed -- can be null if no notification is required.

s - the initial text displayed in the field.

columns - the width of the field.

Method Detail

setConfigureChannel

public void setConfigureChannel(AltingChannelInput configure)

Sets the configuration channel for this ActiveTextEnterField. 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.

setDisableTime

public void setDisableTime(long disableTime)

This is used to set the time during which the text field is disabled after an ENTER or ESCAPE has been entered.

NOTE: This may only be called before this process is run.

Parameters:

disableTime - the disable time after an ENTER or ESCAPE.

getActiveTextField

public ActiveTextField getActiveTextField()

This is used to get the ActiveTextField within this component so that it can be configured (using TextField or ActiveTextField methods) or added to some container. For example, event channels can be added by invoking getActiveTextField().addXXXEventChannel(...).

NOTE: such configuration must be finished before this process is run.

NOTE: do not use this method to set a configure channel - use an appropriate constructor or setConfigureChannel.

Returns:

the ActiveTextField within this component.

run

public void run()

The main body of this process.

Specified by:

run in interface CSProcess