Service class does not run - multithreading

Question

I have the following section of JavaFX that implements Service class:
public void processingImage() {
Task<Void> track = new Task<Void>() {
#Override
protected Void call() throws Exception {
while (true) {
if (flag == false) {
if (someCondition) {
flag = true;
CommunicateServer.sendObject = new Object[2];
CommunicateServer.sendObject[0] = 6;
CommunicateServer.sendObject[1] = "hello";
myService.start();
flag = false;
System.out.println("this line does not print");
}
}
return null;
}
};
Thread th1 = new Thread(track);
th1.setDaemon(true);
th1.start();
}
And the MyService class is implemented as:
private class MyService extends Service<Void> {
#Override
protected Task<Void> createTask() {
return new Task<Void>() {
#Override
protected Void call() throws Exception {
CommunicateServer.callSendObject(CommunicateServer.sendObject, true);
response = CommunicateServer.getObject();
System.out.println("this print should have been many times but only executed once!!!!");
return null;
}
};
}
}
My problem is although I expect the code to print this line does not print, the code actually does not print this. Moreover, the line this print should have been many times but only executed once!!!! is printed only once although I think it should have been printed many times. I don't know how to fix this problem. Any help or suggestion will be met with gratitude.

Answer 1

It's not really clear what you expect your code to do, but Service.start() should be called from the FX Application Thread. Since you are calling it from a background thread, this may be throwing an exception, preventing you reaching the System.out.println(...) statement.
Moreover, the service must be in the READY state to receive the call to start(), so on the second execution (if there is one), since the service has not been reset, you will get an IllegalArgumentException, exiting the call() method in the task defined in processingImage(). Hence your service will execute at most once.