Prev: Calling .NET exec from Java
Next: configure Spring to use jax-ws endpoint to consume XML then produce JSON
From: Marcin Rodzik on 7 May 2010 04:42
Being aware of what has been said http://ow.ly/1I50n http://ow.ly/1I50J
I'd like to ask explicitly: what should I do if I want to display some
information to the user in a Swing GUI app using a JDialog? I know
dialogs are event-driven so that execution of the thread which
requested displaying the dialog stops, but other currently fired
events are still handled.

The thing I don't know and I'd like to is: should I create a Runnable
object and schedule it for execution:

SwingUtilities.invokeAndWait(new Runnable() {
@Override
public void run() {
/* display the dialog here */
}
});

or:

I can simply write the code like this:

JOptionPane.showMessageDialog(parent, msg, title, messageType);

without the SwingUtilities stuff and Swing will handle the code
correctly anyway? I used to follow the first option but now I doubt if
it makes any sense.

regards,
Marcin
From: Lew on 7 May 2010 10:55
Marcin Rodzik wrote:
> Being aware of what has been said <http://ow.ly/1I50nhttp://ow.ly/1I50J>
> I'd like to ask explicitly: what should I do if I want to display some
> information to the user in a Swing GUI app using a JDialog? I know
> dialogs are event-driven so that execution of the thread which
> requested displaying the dialog stops, but other currently fired
> events are still handled.
>
> The thing I don't know and I'd like to is: should I create a Runnable
> object and schedule it for execution:
>
> SwingUtilities.invokeAndWait(new Runnable() {
>   @Override
>   public void run() {
>     /* display the dialog here */
>   }
>
> });
>

Usually the JDialog is raised in response to an event already on the
dispatch thread, but using invokeAndWait() or invokeLater() is fine if
you're already on the EDT.

I don't know why you'd prefer invokeAndWait() over invokeLater().

> or:
>
> I can simply write the code like this:
>
> JOptionPane.showMessageDialog(parent, msg, title, messageType);
>
> without the SwingUtilities stuff and Swing will handle the code
> correctly anyway?
>

Only if you're already on the EDT to start with, otherwise it's a bad
idea.

> I used to follow the first option but now I doubt if
> it makes any sense.
>

Depends on whether you really mean for the caller to wait for the
dialog.

--
Lew

From: John B. Matthews on 7 May 2010 12:25
In article
<1cc05fba-94dd-4ee1-8e67-0e04d303cb7f(a)i9g2000yqi.googlegroups.com>,
Marcin Rodzik <marteno_rodia(a)o2.pl> wrote:

> I know dialogs are event-driven so that execution of the thread which
> requested displaying the dialog stops, but other currently fired
> events are still handled.

Perhaps I misunderstand, but this seems incorrect. A modal dialog
blocks the caller's ability to post new user generated events to the
event dispatch thread (EDT), but the EDT itself continues to process
events. Based on this clarification,

<http://groups.google.com/group/comp.lang.java.programmer/msg/c6ddf50e2b6e1fa1>

this program would seem to be a counter-example:

<http://groups.google.com/group/comp.lang.java.programmer/msg/d95da1f8f9af2339>

> I can simply write the code like this:
>
> JOptionPane.showMessageDialog(parent, msg, title, messageType);
>
> without the SwingUtilities stuff and Swing will handle the code
> correctly anyway?

I would advocate this simpler approach, subject to the caveats adduced
by Lew in a related response.

--
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>
From: Daniel Pitts on 10 May 2010 17:24
On 5/7/2010 1:42 AM, Marcin Rodzik wrote:
> Being aware of what has been said http://ow.ly/1I50n http://ow.ly/1I50J
> I'd like to ask explicitly: what should I do if I want to display some
> information to the user in a Swing GUI app using a JDialog? I know
> dialogs are event-driven so that execution of the thread which
> requested displaying the dialog stops, but other currently fired
> events are still handled.
>
> The thing I don't know and I'd like to is: should I create a Runnable
> object and schedule it for execution:
>
> SwingUtilities.invokeAndWait(new Runnable() {
> @Override
> public void run() {
> /* display the dialog here */
> }
> });
>
> or:
>
> I can simply write the code like this:
>
> JOptionPane.showMessageDialog(parent, msg, title, messageType);
>
> without the SwingUtilities stuff and Swing will handle the code
> correctly anyway? I used to follow the first option but now I doubt if
> it makes any sense.
SwingUtilities is old, use java.awt.EventQueue instead.

Yes, if you are not on the dispatch queue, you should use invokeAndWait
or invokeLater.


--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>
From: Daniel Pitts on 10 May 2010 17:28
On 5/7/2010 7:55 AM, Lew wrote:
> Marcin Rodzik wrote:
>> Being aware of what has been said<http://ow.ly/1I50nhttp://ow.ly/1I50J>
>> I'd like to ask explicitly: what should I do if I want to display some
>> information to the user in a Swing GUI app using a JDialog? I know
>> dialogs are event-driven so that execution of the thread which
>> requested displaying the dialog stops, but other currently fired
>> events are still handled.
>>
>> The thing I don't know and I'd like to is: should I create a Runnable
>> object and schedule it for execution:
>>
>> SwingUtilities.invokeAndWait(new Runnable() {
>> @Override
>> public void run() {
>> /* display the dialog here */
>> }
>>
>> });
>>
>
> Usually the JDialog is raised in response to an event already on the
> dispatch thread, but using invokeAndWait() or invokeLater() is fine if
> you're already on the EDT.
>
> I don't know why you'd prefer invokeAndWait() over invokeLater().
invokeAndWait must *not* be called from the EDT.
One would prefer invokeAndWait if the caller wants to be sure the event
is fully processed before continuing.
> Depends on whether you really mean for the caller to wait for the
> dialog.
Which is a common (if misguided) idiom.

In view code, it makes sense, but if you put it in model/controller
code, you are likely to run into huge problems later.

--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>
 |  Next  |  Last
Pages: 1 2
Prev: Calling .NET exec from Java
Next: configure Spring to use jax-ws endpoint to consume XML then produce JSON