javafx - FX assessing if ListView is empty using different change listeners -

i want assess whether listview empty disable or enable submit button. in essence, when listview has no content button disabled , when has 1 or more elements enabled.

i've managed achieve using listchangelistener, using code such as:

vp.addlistchangelistener(change -> {         change.next();           if (change.getlist().size() == 0 && change.wasremoved() || change.getlist().size() == 1 && change.wasadded()) {             bp.togglesubmitavailability("submit");         }     }); 

where method addlistchangelistener follows:

public void addlistchangelistener(listchangelistener<name> listener) {     names.addlistener(listener); } 

what ideally wanted use traditional changelistener , listen 1 of properties associated listview. example, thought may work:

vp.additemslistener((observable, oldvalue, newvalue) -> {          if (newvalue.size() == 0 && oldvalue.size() > 0 || newvalue.size() == 1 && oldvalue.size() == 0) {             bp.togglesubmitavailability("submit");         }     }); 

where method additemslistener follows (and attaches listener itemsproperty):

public void additemslistener(changelistener<observablelist<name>> listener) {         listview.itemsproperty().addlistener(listener);     } 

however, reason, when add items listview, or add items observablelist attached it, property not being changed, nothing happening - triggers itemsproperty of listview change, , if approach not work, there way did listchangelistener utilising property associated listview (in reasonably elegant way of course)?

the itemsproperty() property holds list itself; listeners registered notified if call listview.setitems(...), (i.e. if list reference changed) not notified if modify content of list contains (i.e. if listview.getitems().add(...)).

the bindings class provides isempty(observablelist) method can use here:

button.disableproperty().bind(bindings.isempty(listview.getitems())); 

or equivalently, listener:

bindings.isempty(listview.getitems()).addlistener(     (obs, wasempty, isnowempty) -> button.setdisable(isnowempty)); 

so implement method this:

public void addemptylistlistener(changelistener<boolean> listener) {     bindings.isempty(listview.getitems()).addlistener(listener); } 

and do

vp.addemptylistlistener((obs, wasempty, isnowempty) -> {     // ... });