frysk.rt
Class UpdatingDisplayValue

java.lang.Object
  frysk.rt.DisplayValue
      frysk.rt.UpdatingDisplayValue

public class UpdatingDisplayValue
extends DisplayValue

An UpdatingDisplayValue is nearly identical to a DisplayValue, except that an UpdatingDisplayValue is provided with additional information that enables it to automatically refresh itself whenever the task given to it changes state. Objects can be notified of updates by using the addObserver method.

Nested Class Summary

private class	UpdatingDisplayValue.LockObserver
private class	UpdatingDisplayValue.TermObserver

Field Summary

private boolean	enabled
private SteppingEngine	engine
private UpdatingDisplayValue.LockObserver	lock
private List	observers
private byte[]	oldValue
private UpdatingDisplayValue.TermObserver	term

Fields inherited from class frysk.rt.DisplayValue

frameIdentifier, myTask, myVar, num, varLabel

Constructor Summary

UpdatingDisplayValue(String name, Task task, FrameIdentifier fIdent, SteppingEngine eng, int id)
Crate a new UpdatingDisplayValue

Method Summary

void	addObserver(DisplayValueObserver obs) Adds an observer to listen for changes to this DisplayValue
protected boolean	arrayChanged(byte[] newArray)
void	disable() Disables the display, stopping all notification of changes to the underlying expression.
void	enable() Re-enables the display, resuming notification of events to all observers
boolean	equals(Object other)
boolean	isEnabled() Check if this display is enabled or not.
protected void	notifyObserversAvailable()
protected void	notifyObserversDisabled()
protected void	notifyObserversUnavailableOutOfScope()
protected void	notifyObserversUnavailableTaskResumed()
protected void	notifyObserversValueChanged()
void	refresh() Updates the display to refect the new variable value
boolean	removeObserver(DisplayValueObserver obs) Removes the given observer from the list of observers

Methods inherited from class frysk.rt.DisplayValue

getFrameIdentifier, getId, getName, getTask, getValue, isAvailable

Methods inherited from class java.lang.Object

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

Field Detail

engine

private SteppingEngine engine

observers

private List observers

oldValue

private byte[] oldValue

lock

private UpdatingDisplayValue.LockObserver lock

term

private UpdatingDisplayValue.TermObserver term

enabled

private boolean enabled

Constructor Detail

UpdatingDisplayValue

UpdatingDisplayValue(String name,
                     Task task,
                     FrameIdentifier fIdent,
                     SteppingEngine eng,
                     int id)

Crate a new UpdatingDisplayValue

Parameters:

name - The name of the variable to track

task - The task from which to track the variable

fIdent - The frame identifier corresponding to the scope from which the variable should be read

eng - The stepping engine to monitor for changes in execution state

id - The unique id for this display

Method Detail

refresh

public void refresh()

Description copied from class: DisplayValue

Updates the display to refect the new variable value

Overrides:

refresh in class DisplayValue

addObserver

public void addObserver(DisplayValueObserver obs)

Adds an observer to listen for changes to this DisplayValue

Parameters:

obs - The new observer to be notified

removeObserver

public boolean removeObserver(DisplayValueObserver obs)

Removes the given observer from the list of observers

Parameters:

obs - The observer to remove

Returns:

True if obs was found and removed, false otherwise

equals

public boolean equals(Object other)

Overrides:

equals in class Object

disable

public void disable()

Disables the display, stopping all notification of changes to the underlying expression.

enable

public void enable()

Re-enables the display, resuming notification of events to all observers

isEnabled

public boolean isEnabled()

Check if this display is enabled or not. A disabled display will not send any notifications regarding changes to the value of the watched expression.

Returns:

True iff this display is enabled, false otherwise

notifyObserversAvailable

protected void notifyObserversAvailable()

notifyObserversUnavailableTaskResumed

protected void notifyObserversUnavailableTaskResumed()

notifyObserversValueChanged

protected void notifyObserversValueChanged()

notifyObserversUnavailableOutOfScope

protected void notifyObserversUnavailableOutOfScope()

notifyObserversDisabled

protected void notifyObserversDisabled()

arrayChanged

protected boolean arrayChanged(byte[] newArray)