echopoint
Class Timer

java.lang.Object
  nextapp.echo.Component
      echopoint.Timer

All Implemented Interfaces:

ReflectionSetter, java.io.Serializable

public class Timer

extends nextapp.echo.Component

implements ReflectionSetter

The Timer class is a Component that causes an action to occur at a predefined rate.
Each Timer has a list of ActionListeners and a delay ( the time between actionPerfomed() calls).
When delay milliseconds have passed, a Timer sends the actionPerformed() message to its listeners.
This cycle repeats until stop() is called, or halts immediately if the Timer is configured to send its message just once.
Note that this is a very coarse timer. The timer is run on the client and the timeout must travel back to the server before any other code can be notified of this event. Therefore the granuality of the timer cannot be gaurunteed, as it depends on the client speed and the network speed between the client and server.
This class is mostly useful for causing the client to update without having to have the user click on anything.
You can only have one effective Timer on a Window at a time. This is because once the lowest delay timer has popped, any screen updates will cause all Timers on that Window to be reset to their respective starting delays, regardless of how much time has passed since the last event happened on a given timer.
The reason the Timer is fired on the client rather than via a thread on the server, is to help support many clients (thousands). Each client is running their own timers, using their own processing power. If a single thread was created for all Timers (or worse one per client) then the system would eventually grind to a halt.

Author:

Brad Baker

See Also:

Serialized Form

Field Summary

static java.lang.String

TIMER_CHANGED_PROPERTY

Fields inherited from class nextapp.echo.Component

BACKGROUND_CHANGED_PROPERTY, CHILDREN_CHANGED_PROPERTY, ENABLED_CHANGED_PROPERTY, FONT_CHANGED_PROPERTY, FOREGROUND_CHANGED_PROPERTY, IDENTIFIER_CHANGED_PROPERTY, listenerList, LOCALE_CHANGED_PROPERTY, MODEL_CHANGED_PROPERTY, STYLE_BACKGROUND, STYLE_FONT, STYLE_FOREGROUND, UPDATE_PROPERTY, VISIBLE_CHANGED_PROPERTY

Constructor Summary

Timer()
Creates a Timer that will notify its listeners every 1000 milliseconds.

Timer(int delay)
Creates a Timer that will notify its listeners every delay milliseconds.

Timer(int delay, nextapp.echo.event.ActionListener actionListener)
Creates a Timer that will notify its listeners every delay milliseconds.

Method Summary

void	addActionListener(nextapp.echo.event.ActionListener l) Adds an ActionListener to the Timer.
void	fireActionPerformed(nextapp.echo.event.ActionEvent e) Notifies all listeners that have registered for this event type.
java.lang.String	getActionCommand()
int	getDelay()
int	getInitialDelay()
boolean	hasFired()
boolean	isRepeats() Returns true if the Timer will send a actionPerformed() message to its listeners multiple times.
boolean	isRunning()
void	removeActionListener(nextapp.echo.event.ActionListener l) Removes an ActionListener from the Timer.
void	restart() Restarts a Timer, canceling any pending firings, and causing it to fire with its initial dely.
java.lang.Object	set(java.lang.reflect.Field field, java.lang.Object newValue) Called to save the old value of a field, set in a new value and return the old value of a field.
void	setActionCommand(java.lang.String newValue) Sets the Timer's action command.
void	setDelay(int newValue) Sets the Timer's delay, the number of milliseconds between successive actionPerfomed() messages to its listeners This methods fires a PropertyChangeEvent with a getPropertyName() value of Timer.TIMER_CHANGED_PROPERTY
void	setInitialDelay(int newValue) Sets the Timer's initial delay.
void	setRepeats(boolean newValue) Instructs the Timer to send actionPerformed() to its listeners only once, and then stop.
void	start() Starts the Timer, causing it to send actionPerformed() messages to its listeners.
void	stop() Stops the Timer, causing it to stop sending actionPerformed() messages to its listeners.

Methods inherited from class nextapp.echo.Component

add, add, addHierarchyListener, addPropertyChangeListener, applyStyle, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getBackground, getComponent, getComponentCount, getComponents, getEchoInstance, getFont, getForeground, getIdentifier, getLocale, getParent, indexOf, init, isAncestorOf, isEnabled, isRegistered, isShowing, isVisible, remove, remove, removeAll, removeHierarchyListener, removePropertyChangeListener, setBackground, setEnabled, setFont, setForeground, setIdentifier, setLocale, setVisible, update, validate

Methods inherited from class java.lang.Object

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

Field Detail

TIMER_CHANGED_PROPERTY

public static final java.lang.String TIMER_CHANGED_PROPERTY

See Also:

Constant Field Values

Constructor Detail

Timer

public Timer()

Creates a Timer that will notify its listeners every 1000 milliseconds.

Timer

public Timer(int delay)

Creates a Timer that will notify its listeners every delay milliseconds.

Timer

public Timer(int delay,
             nextapp.echo.event.ActionListener actionListener)

Creates a Timer that will notify its listeners every delay milliseconds.

Method Detail

addActionListener

public void addActionListener(nextapp.echo.event.ActionListener l)

Adds an ActionListener to the Timer.

Parameters:

l - The ActionListener to be added.

fireActionPerformed

public void fireActionPerformed(nextapp.echo.event.ActionEvent e)

Notifies all listeners that have registered for this event type.

Parameters:

e - The ActionEvent to send.

getActionCommand

public java.lang.String getActionCommand()

Returns:

the action command for the Timer

getDelay

public int getDelay()

Returns:

The delay in milliseconds of the Timer.

getInitialDelay

public int getInitialDelay()

Returns:

The initial delay in milliseconds of the Timer.

hasFired

public boolean hasFired()

Returns:

true if the Timer has fired before

isRepeats

public boolean isRepeats()

Returns true if the Timer will send a actionPerformed() message to its listeners multiple times.

isRunning

public boolean isRunning()

Returns:

true of the Timer is running.

removeActionListener

public void removeActionListener(nextapp.echo.event.ActionListener l)

Removes an ActionListener from the Timer.

Parameters:

l - The ActionListener to be removed.

restart

public void restart()

Restarts a Timer, canceling any pending firings, and causing it to fire with its initial dely.

setActionCommand

public void setActionCommand(java.lang.String newValue)

Sets the Timer's action command.

Parameters:

newValue - The new action command for this timer.

setDelay

public void setDelay(int newValue)

Sets the Timer's delay, the number of milliseconds between successive actionPerfomed() messages to its listeners
This methods fires a PropertyChangeEvent with a getPropertyName() value of Timer.TIMER_CHANGED_PROPERTY

setInitialDelay

public void setInitialDelay(int newValue)

Sets the Timer's initial delay. This will be used for the first "ringing" of the Timer only. Subsequent ringings will be spaced using the delay property.
This methods fires a PropertyChangeEvent with a getPropertyName() value of Timer.TIMER_CHANGED_PROPERTY

setRepeats

public void setRepeats(boolean newValue)

Instructs the Timer to send actionPerformed() to its listeners only once, and then stop.
This methods fires a PropertyChangeEvent with a getPropertyName() value of Timer.TIMER_CHANGED_PROPERTY

start

public void start()

Starts the Timer, causing it to send actionPerformed() messages to its listeners.

stop

public void stop()

Stops the Timer, causing it to stop sending actionPerformed() messages to its listeners.

set

public java.lang.Object set(java.lang.reflect.Field field,
                            java.lang.Object newValue)
                     throws java.lang.Exception

Description copied from interface: ReflectionSetter

Called to save the old value of a field, set in a new value and return the old value of a field. This interface allows a field set operation to be "delegated" back into the class that has permission to perform the field set.

 public Object set(Field f, Object newValue) throws Exception {
      Object oldValue = f.get(this);
      f.set(this,newValue);
      return oldValue;
 }
 

Specified by:

set in interface ReflectionSetter

Parameters:

field - - the field to be set

newValue - - the new value to be set

Returns:

the oldValue of the field

Throws:

java.lang.Exception

See Also:

ReflectionSetter.set(Field, Object)