Problem with java swing button and loop

Question

Problem with java swing button and loop
I�m using VAJ 4.0. and I�m doing normal GUI application. I have next problem.
I have in the same class two jswing buttons named start (ivjGStart) and stop (ivjGStop) and private static int field named Status where initial value is 0. This buttons should work something like this:
When I click on start button it must do next:
Start button must set disenabled and Stop button must set enabled and selected. Field status is set to 1, because this is a condition in next procedure in some loop. And then procedure named IzvajajNeprekinjeno() is invoked.
And when I click on stop button it must do next:
Start button must set enabled and selected and Stop button must set disenabled.
Field status is set to 0.
This works everything fine without loop �do .. while� inside the procedure IzvajajNeprekinjeno(). But when used this loop the start button all the time stay (like) pressed. And this means that a can�t stop my loop.
There is java code, so you can get better picture:
/** start button */
public void gStart_ActionEvents() {
try {
ivjGStart.setEnabled(false);
ivjGStop.setEnabled(true);
ivjGStop.setSelected(true);
getJTextPane1().setText("Program is running ...");
Status = 1;
} catch (Exception e) {}
/** stop button */
public void gStop_ActionEvents() {
try {
ivjGStart.setEnabled(true);
ivjGStart.setSelected(true);
ivjGStop.setEnabled(false);
getJTextPane1().setText("Program is NOT running ...");
Status = 0;
} catch (Exception e) {
/** procedure IzvajajNeprekinjeno() */
public void IzvajajNeprekinjeno() {  //RunLoop
try {
int zamik = 2000; //delay
do {
Thread.sleep(zamik);
PreberiDat(); //procedure
} while (Status == 1);
} catch (Exception e) {
So, I'm asking what I have to do, that start button will not all the time stay pressed? Or some other aspect of solving this problem.
Any help will be appreciated.
Best regards,
Tomi

Answer 1

This is a multi thread problem. When you start the gui, it is running in one thread. Lets call that GUI_Thread so we know what we are talking about.
Since java is task-based this will happen if you do like this:
1. Button "Start" is pressed. Thread running: GUI_Thread
2. Event gStart_ActionEvents() called. Thread running: GUI_Thread
3. Method IzvajajNeprekinjeno() called. Thread running: GUI_Thread
4. Sleep in method IzvajajNeprekinjeno() on thread GUI_Thread
5. Call PreberiDat(). Thread running: GUI_Thread
6. Check status. If == 1, go tho 4. Thread running: GUI_Thread.
Since the method IzvajajNeprekinjeno() (what does that mean?) and the GUI is running in the same thread and the event that the Start button has thrown isn't done yet, the program will go on in the IzvajajNeprekinjeno() method forever and never let you press the Stop-button.
What you have to do is do put either the GUI in a thread of its own or start a new thread that will do the task of the IzvajajNeprekinjeno() method.
http://java.sun.com/docs/books/tutorial/uiswing/index.html
This tutorial explains how to build a multi threaded gui.
/Lime