IllegalStateException on an observable list

[Jonathan Giles]

This is a common mistake. You must, inside the onChanged method, loop 
through the changes as such:

while (changes.next()) {
    // put your for loop here
}

I agree the exception is not clear - I would love to see an improved 
error message in the exception to clarify what people need to do.

-- Jonathan

On 22/10/2012 8:37 a.m., Tom Eugelink wrote:
> I have two observable lists; one containing appointments, the other 
> containing selected appointments. If an appointment is removed from 
> the first list, it also must be removed from the second. For this I 
> setup a listener on the first list to handle this:
>
>         // when appointments are removed, they can't be selected anymore
>         appointments.addListener(new 
> ListChangeListener<Agenda.Appointment>()
>         {
>             @Override
>             public void 
> onChanged(javafx.collections.ListChangeListener.Change<? extends 
> Appointment> changes)
>             {
>                 for (Appointment lAppointment : changes.getRemoved())
>                 {
>                     selectedAppointments.remove(lAppointment);
>                 }
>             }
>         });
>
> when constructing the control I get the following exception on the 
> getRemoved() call.
>
> Caused by: java.lang.IllegalStateException
>     at 
> com.sun.javafx.collections.NonIterableChange.checkState(NonIterableChange.java:101)
>     at 
> com.sun.javafx.collections.NonIterableChange$SimpleAddChange.getRemoved(NonIterableChange.java:158)
>     at jfxtras.labs.scene.control.Agenda$1.onChanged(Agenda.java:108)
>     at 
> com.sun.javafx.collections.ListListenerHelper$SingleChange.fireValueChangedEvent(ListListenerHelper.java:134)
>     at 
> com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:48)
>     at 
> com.sun.javafx.collections.ObservableListWrapper.callObservers(ObservableListWrapper.java:97)
>     at 
> com.sun.javafx.collections.ObservableListWrapper.addAll(ObservableListWrapper.java:171)
>     at 
> com.sun.javafx.collections.ObservableListWrapper.addAll(ObservableListWrapper.java:160)
>     at 
> com.sun.javafx.collections.ObservableListWrapper.addAll(ObservableListWrapper.java:309)
>     at 
> jfxtras.labs.scene.control.AgendaTrial1.start(AgendaTrial1.java:122)
>     at 
> com.sun.javafx.application.LauncherImpl$5.run(LauncherImpl.java:319)
>     at 
> com.sun.javafx.application.PlatformImpl$5.run(PlatformImpl.java:206)
>     at 
> com.sun.javafx.application.PlatformImpl$4.run(PlatformImpl.java:173)
>     at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
>     at 
> com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:29)
>     at 
> com.sun.glass.ui.win.WinApplication$2$1.run(WinApplication.java:62)
>     ... 1 more
>
> Can someone explain why? And how to work around that?
>
> Tom
>
>