JavaFX, Is there any callback for Platform.runlater()? - javafx

Question

My application adds multiple Runnable on FX thread, by calling Platform.runlater method, then, I want to do some calculations only when there is no additional Runnable is in the FX Platform queue.
But I don't know the right way, is there any event or callback mechanism to get the right time?
Currently I force the application thread to sleep randomly MILLISECONDS.

Answer 1

This is a bad idea from the start since you do not know what other code uses Platform.runLater. Also you should not rely on such implementation details; for all you know the queue could never be empty.
However you could post those Runnables using a custom class that keeps track of the number of Runnables and notifies you when all are done:
public class UpdateHandler {
private final AtomicInteger count;
private final Runnable completionHandler;
public UpdateHandler(Runnable completionHandler, Runnable... initialTasks) {
if (completionHandler == null || Stream.of(initialTasks).anyMatch(Objects::isNull)) {
throw new IllegalArgumentException();
}
count = new AtomicInteger(initialTasks.length);
this.completionHandler = completionHandler;
for (Runnable r : initialTasks) {
startTask(r);
}
}
private void startTask(Runnable runnable) {
Platform.runLater(() -> {
runnable.run();
if (count.decrementAndGet() == 0) {
completionHandler.run();
}
});
}
public void Runnable runLater(Runnable runnable) {
if (runnable == null) {
throw new IllegalArgumentException();
}
count.incrementAndGet();
startTask(runnable);
}
}