Handling and Raising events

[Kent]

I have a Synchronizer class. I want it to raise an event every X seconds if
conditions Y & Z are True. Here's what I have already:

public class Synchronizer implements ActionListener
{
timer Synchr; //swing timer

public Synchronizer(int interval)
{
timer Synchr = new timer(interval, this);
}
/**
When the Y & Z set to true, the class will allow timer events to pass.
*/
public void actionPerformed(ActionEvent e)
{
if (Y && Z)
{
raiseEvent();
}
}
/**
I want to raise my own events.
*/
public void raiseEvent()
{
// What goes here?
}
// other methods here... [including some to call raiseEvent()]
boolean Y;
boolean Z;
}

TIA
Kent

[Kent (2)]

Nice name :-)

Your class will need to maintain a set of event listeners. These listeners
should be configurable via methods such as:

void addActionListener(ActionListener listener);

ActionListener removeActionListener(ActionListener listener);

Assume the listeners are in a private ArrayList called actionListeners:

private void raiseEvent() {
ActionEvent event = ...; //construct appropriate event here

for (int i = 0; i < actionListeners.size(); ++i) {
((ActionListener) actionListeners.get(i)).actionPerformed(event);
//invoke each actionPerformed() method on every listener
}
}

Notice I declared raiseEvent() as private. This is because your class should
be responsible for invoking this not anyone else.

Hope that helps,
Kent

"Kent" <file_delete@hotmail.com> wrote:
>I have a Synchronizer class. I want it to raise an event every X seconds
if
>conditions Y & Z are True. Here's what I have already:
>
>public class Synchronizer implements ActionListener
>{
> timer Synchr; //swing timer
>
> public Synchronizer(int interval)
> {
> timer Synchr = new timer(interval, this);
> }
>/**
> When the Y & Z set to true, the class will allow timer events to pass.
>*/
> public void actionPerformed(ActionEvent e)
> {
> if (Y && Z)
> {
> raiseEvent();
> }
> }
>/**
> I want to raise my own events.
>*/
> public void raiseEvent()
> {
> // What goes here?
> }
>// other methods here... [including some to call raiseEvent()]
> boolean Y;
> boolean Z;
>}
>
>TIA
>Kent
>
>

[Kent]

Thanks. I'm sorta used to it ;-)

What I envisioned was having my class, an animation/model, work in either a
single-step mode or in continuous play mode. When in continuous play mode,
the animation would be based on the output of a timer. When in single-step
mode, it would advance based on clicks of a button. If I capture these
events in a 'sychronizer' class, the 'sychronizer' class would contain the
logic to decide whether the timer events got passed on or whether the button
events did. I reasoned that the easy way to do this was to listen for these
events and raise my own 'sychronizer' event when appropriate. Then my
animation just needed to play/advance one step/event that it received from
the 'sychronizer' class; No 'play mode; logic in the animation.

I guess that I'm stuck on this: how**exactly** do I raise an event? Do you
have a simple example of raising an event?

Kent

"Kent (2)" <kb@essential.com.au> wrote in message
news:3deabc9a$1@tnews.web.devx.com...
>
> Nice name :-)
>
> Your class will need to maintain a set of event listeners. These listeners
> should be configurable via methods such as:
>
> void addActionListener(ActionListener listener);
>
> ActionListener removeActionListener(ActionListener listener);
>
> Assume the listeners are in a private ArrayList called actionListeners:
>
> private void raiseEvent() {
> ActionEvent event = ...; //construct appropriate event here
>
> for (int i = 0; i < actionListeners.size(); ++i) {
> ((ActionListener) actionListeners.get(i)).actionPerformed(event);
> //invoke each actionPerformed() method on every listener
> }
> }
>
> Notice I declared raiseEvent() as private. This is because your class
should
> be responsible for invoking this not anyone else.
>
> Hope that helps,
> Kent
>
> "Kent" <file_delete@hotmail.com> wrote:
> >I have a Synchronizer class. I want it to raise an event every X seconds
> if
> >conditions Y & Z are True. Here's what I have already:
> >
> >public class Synchronizer implements ActionListener
> >{
> > timer Synchr; //swing timer
> >
> > public Synchronizer(int interval)
> > {
> > timer Synchr = new timer(interval, this);
> > }
> >/**
> > When the Y & Z set to true, the class will allow timer events to pass.
> >*/
> > public void actionPerformed(ActionEvent e)
> > {
> > if (Y && Z)
> > {
> > raiseEvent();
> > }
> > }
> >/**
> > I want to raise my own events.
> >*/
> > public void raiseEvent()
> > {
> > // What goes here?
> > }
> >// other methods here... [including some to call raiseEvent()]
> > boolean Y;
> > boolean Z;
> >}
> >
> >TIA
> >Kent
> >
> >
>

[Kent]

An event is nothing more than a method call really. As you say, your Synchronizer
class will need to know whether to raise events via the timer or via a user-initiated
action (ie. button click). No matter why the event is being raised it should
be raised in the same fashion.

What you need to decide is whether you will use a built-in event type (ActionEvent
is a good candidate) or define your own. Listeners of your event should implement
an interface (ActionListener corresponds to the ActionEvent) and your Synchronizer
should maintain a list of listeners. The only listener in your case will
be the animating class so it knows when to update the animation.

To actually 'raise' or 'post' an event all you do is create an instance of
ActionEvent and call a method on each listener. This method is defined in
the ActionListener interface and takes an argument of type ActionEvent.

So when do you raise the event? Well, your Synchronizer class should track
whether the timer is being used or is 'paused'. If it is being used then
the event should be posted every time the timer is 'up'. If it isn't being
used, you should have a method in your public interface that allows the event
to be explicitly posted. You may want to set up your ActionEvent object slightly
differently in each case to indicate why /how the event was raised.

BTW, you can see examples of event raising and what-not in the JDK source.
Just look at the swing code for javax.swing.AbstractButton for example.

Regards,
Kent


"Kent" <file_delete@hotmail.com> wrote:
>Thanks. I'm sorta used to it ;-)
>
>What I envisioned was having my class, an animation/model, work in either
a
>single-step mode or in continuous play mode. When in continuous play mode,
>the animation would be based on the output of a timer. When in single-step
>mode, it would advance based on clicks of a button. If I capture these
>events in a 'sychronizer' class, the 'sychronizer' class would contain the
>logic to decide whether the timer events got passed on or whether the button
>events did. I reasoned that the easy way to do this was to listen for these
>events and raise my own 'sychronizer' event when appropriate. Then my
>animation just needed to play/advance one step/event that it received from
>the 'sychronizer' class; No 'play mode; logic in the animation.
>
>I guess that I'm stuck on this: how**exactly** do I raise an event? Do you
>have a simple example of raising an event?
>
>Kent
>
>"Kent (2)" <kb@essential.com.au> wrote in message
>news:3deabc9a$1@tnews.web.devx.com...
>>
>> Nice name :-)
>>
>> Your class will need to maintain a set of event listeners. These listeners
>> should be configurable via methods such as:
>>
>> void addActionListener(ActionListener listener);
>>
>> ActionListener removeActionListener(ActionListener listener);
>>
>> Assume the listeners are in a private ArrayList called actionListeners:
>>
>> private void raiseEvent() {
>> ActionEvent event = ...; //construct appropriate event here
>>
>> for (int i = 0; i < actionListeners.size(); ++i) {
>> ((ActionListener) actionListeners.get(i)).actionPerformed(event);
>> //invoke each actionPerformed() method on every listener
>> }
>> }
>>
>> Notice I declared raiseEvent() as private. This is because your class
>should
>> be responsible for invoking this not anyone else.
>>
>> Hope that helps,
>> Kent
>>
>> "Kent" <file_delete@hotmail.com> wrote:
>> >I have a Synchronizer class. I want it to raise an event every X seconds
>> if
>> >conditions Y & Z are True. Here's what I have already:
>> >
>> >public class Synchronizer implements ActionListener
>> >{
>> > timer Synchr; //swing timer
>> >
>> > public Synchronizer(int interval)
>> > {
>> > timer Synchr = new timer(interval, this);
>> > }
>> >/**
>> > When the Y & Z set to true, the class will allow timer events to pass.
>> >*/
>> > public void actionPerformed(ActionEvent e)
>> > {
>> > if (Y && Z)
>> > {
>> > raiseEvent();
>> > }
>> > }
>> >/**
>> > I want to raise my own events.
>> >*/
>> > public void raiseEvent()
>> > {
>> > // What goes here?
>> > }
>> >// other methods here... [including some to call raiseEvent()]
>> > boolean Y;
>> > boolean Z;
>> >}
>> >
>> >TIA
>> >Kent
>> >
>> >
>>
>
>
>