JNI C++ importatn process

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Marcelo - 30 Sep 2005 16:22 GMT

Hi,

I have a problem with my JNI application. Actually the C++ application
that is called from my java program is very very important. Because the
calculations last a lot of the time, I would like to know how to manage
them like as background thread.

I am using a link between GUI and C++, but with this calculation
problem, the GUI gets blocked.

what can I do?

Marcelo

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Andrew Thompson - 30 Sep 2005 16:56 GMT

> I am using a link between GUI and C++, but with this calculation
> problem, the GUI gets blocked.
>
> what can I do?

Hand the call to the JNI code off to a Thread..
<http://www.physci.org/guifaq.jsp#2.1>
..then give the end user a 'progress dialog' (or something)
<http://www.physci.org/guifaq.jsp#2.2>

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Marcelo - 30 Sep 2005 17:39 GMT

because it is inside a GUI
should I use a SwingUtilities ?

javax.swing.SwingUtilities.invokeLater(new Runnable() {
    public void run() {
        greatC++();
    }
});

thanks

Marcelo

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Thomas Fritsch - 30 Sep 2005 18:35 GMT

> because it is inside a GUI
> should I use a SwingUtilities ?
[quoted text clipped - 4 lines]
> }
> });

NOOOO! With SwingUtilities.invokeLater you tell Java to call greatC++()
from the GUI(!) thread. Hence the GUI will be blocked as long as it runs
greatC++().
Instead you want greatC++() to be called by ANOTHER thread. Create a new
Thread and then start it by yourself.
I recommend reading a good text-book (or the Java tutorial) about the
Thread and Runnable stuff.

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Roedy Green - 30 Sep 2005 21:18 GMT

>javax.swing.SwingUtilities.invokeLater(new Runnable() {
>    public void run() {
>        greatC++();
>    }
>});

Definitely not. Everything will come to grinding halt when that great
c task hogs the Swing event thread. You need a NEW background thread
to run your big task on.

See http://mindprod.com/jgloss/thread.html

In particular look at the SwingWorker class.

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Canadian Mind Products, Roedy Green.
http://mindprod.com Again taking new Java programming contracts.

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Marcelo - 03 Oct 2005 12:59 GMT

thanks a lot,

Marcelo

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JNI C++ importatn process

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