I’m looking for a way to stop a “process” or a “thread”. i have a method in mxj which is called when i change the value of a number box in max, and this method executes a drawing-thread to draw something which can, sometimes, be slow. (if a change the value very fast in max, the method doesn’t have time to compute everytime)

So, i’d like, that, when the method is called, it tests to see if the drawing-thread is already running (from a previous method call), and if it’s the case, that it delete the thread and restart it. i’m not sure how to do that. first i managed to create a thread inside my method, with :

public void redraw_because_value_changed( int value_from_max ) {
…
( new Thread() { public void run() {
…// the drawing stuff …
}}).start();
}

This works fine, but will create many threads if the drawing is slow while i change the value in max, causing slow down. But then i tried to name the thread, and delete it before restarting a new one, and first, this works a little, but when i change my value very fast in max5, it crashes. :

Thread curveThread;

public void redraw_because_value_changed( int value_from_max ) {
…
curveThread = null ;
( curveThread = new Thread() { public void run() {
…// the drawing stuff …
}}).start();
}

I not sure to understand well how to manage this. In the “flies.java” example, there’s an other example on managing threads, but i can’t figure out how it works plus the need in “flies” is different.

Thanks a lot for any help.

Alexandre.

to me this problem is more related to general threading issues than to
mxj programming. I think the Sun Tutorial on concurrency,

http://java.sun.com/docs/books/tutorial/essential/concurrency/index.html

would be a good starting point for you. In my opinion, it will be far
enough at this point for you to read it just until the end of the first
big paragraph (called Thread Objects).

Hope this helps,
Adam

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Alexandre wrote:
> Hi,
>
> I’m looking for a way to stop a “process” or a “thread”. i have a method in mxj which is called when i change the value of a number box in max, and this method executes a drawing-thread to draw something which can, sometimes, be slow. (if a change the value very fast in max, the method doesn’t have time to compute everytime)
>
> So, i’d like, that, when the method is called, it tests to see if the drawing-thread is already running (from a previous method call), and if it’s the case, that it delete the thread and restart it. i’m not sure how to do that. first i managed to create a thread inside my method, with :
>
> public void redraw_because_value_changed( int value_from_max ) {
> …
> ( new Thread() { public void run() {
> …// the drawing stuff …
> }}).start();
> }
>
> This works fine, but will create many threads if the drawing is slow while i change the value in max, causing slow down. But then i tried to name the thread, and delete it before restarting a new one, and first, this works a little, but when i change my value very fast in max5, it crashes. :
>
>
> Thread curveThread;
>
> public void redraw_because_value_changed( int value_from_max ) {
> …
> curveThread = null ;
> ( curveThread = new Thread() { public void run() {
> …// the drawing stuff …
> }}).start();
> }
>
>
> I not sure to understand well how to manage this. In the “flies.java” example, there’s an other example on managing threads, but i can’t figure out how it works plus the need in “flies” is different.
>
>
> Thanks a lot for any help.
>
> Alexandre.
>
>
>

You may find this information helpful:

http://java.sun.com/javase/6/docs/technotes/guides/concurrency/threadPrimitiveDeprecation.html

Also, on the Max side, you should consider using a speedlim object between your number box and mxj.

In fact, looking completly at your links, it’s looking like there no way to stop a thread without testing inside itself, with methods like “Thread.interrupted” or “catch (InterruptedException e)”:

“What if a thread goes a long time without invoking a method that throws InterruptedException? Then it must periodically invoke Thread.interrupted, which returns true if an interrupt has been received.” ( http://java.sun.com/docs/books/tutorial/essential/concurrency/interrupt.html )

mmh.. This stop() method from “java.lang.Thread” , is now deprecated for complicated reasons. So, if i have to test from inside my loops, to continue or to “break”, i just can use effectivly a kind of “runAgain” booleen, defined in the class (or “volatile”?.. an other concept to learn for me), which can ask the thread to stop. (when the booleen is tested at each end of my heavy-drawing-loop) Without any need to bother myself with new methods with which i’m not confortable with.

But, is it really sure that there no way to stop a thread without introducing testing stuff periodically in the thread itself ?

Well, i might post this question to a java forum, but for now, i just realised that a big part of my drawing time was, actually, the call of com.cycling74.jitter.JitterMatrix.copyBufferedImage : 100 milliseconds!… (for a 1200*700 image)
I posted a new topic for this new problem.

Thanks,
Alexandre

Yes – the reason stop() was deprecated was partly because the only way
of telling if it’s safe to stop a thread is from within.

–
Owen

> mmh.. This stop() method from “java.lang.Thread” , is now deprecated
> for complicated reasons.

Complicated, but quite important: if you start writing multithreaded
code you’ll have to understand semaphores. In other words, threading
is subtle and quick to anger. But if you keep it simple and keep a
clear head, it’s manageable.

– N.

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