How to get all listeners to an observable value? I could extend the class and override addListener
and removeListener
methods to store them in a set. But the set should already be stored somehow inside observable value. How could I get that set?
I find a way around it, you can't get direct access to the Listeners list but if you use a debugger(I use IntelliJ) you can see it if you look inside your ObservableProprty like this:(I hope this is clear enough)
another way:(You're a smart guy, you'll know how to fit into your case)
//SimpleFloatProperty we want to find its Listeners
FloatPropertyBase f=ampPS.currentProperty();
Object value;
ChangeListener[] list;
ChangeListener changeListener=null;
Field field = null;
try {
field = FloatPropertyBase.class.getDeclaredField("helper");
field.setAccessible(true);
value = field.get(f);
try {
field = value.getClass().getDeclaredField("listener");
field.setAccessible(true);
changeListener =(WeakChangeListener)field.get(value);
}catch (NoSuchFieldException e) {
e.printStackTrace();
}
try {
field = value.getClass().getDeclaredField("changeListeners");
field.setAccessible(true);
list =(ChangeListener[])field.get(value);
}catch (NoSuchFieldException e) {
e.printStackTrace();
}
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
the result:
(Notice the difference between 1 listener or more than 1)
I I'm adding Example for several types of values
public static ChangeListener[] getChangeListeners(ObservableValue observableValue){
Object value;
ChangeListener[] list=null;
ChangeListener changeListener=null;
Field field = null;
try {
if(observableValue instanceof SimpleFloatProperty ){
field = FloatPropertyBase.class.getDeclaredField("helper");
}
else if(observableValue instanceof SimpleBooleanProperty ){
field = BooleanPropertyBase.class.getDeclaredField("helper");
}
else if(observableValue instanceof SimpleIntegerProperty ){
field = IntegerPropertyBase.class.getDeclaredField("helper");
}
field.setAccessible(true);
value = field.get(observableValue);
try {
field = value.getClass().getDeclaredField("listener");
field.setAccessible(true);
changeListener =(ChangeListener)field.get(value);
}catch (NoSuchFieldException e) {
//e.printStackTrace();
}
try {
field = value.getClass().getDeclaredField("changeListeners");
field.setAccessible(true);
list =(ChangeListener[])field.get(value);
}catch (NoSuchFieldException e) {
//e.printStackTrace();
}
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
if(list!=null){
return list;
}
else {
ChangeListener[] changeListeners = new ChangeListener[1];
changeListeners[0]=changeListener;
return changeListeners;
}
}
and I call it:
SimpleBooleanProperty booleanProperty = new SimpleBooleanProperty(true);
SimpleFloatProperty simpleFloatProperty = new SimpleFloatProperty(0);
SimpleIntegerProperty simpleIntegerProperty = new SimpleIntegerProperty(1);
booleanProperty.addListener(changeListener);
simpleFloatProperty.addListener(changeListener);
simpleIntegerProperty.addListener(changeListener);
simpleIntegerProperty.addListener(changeListener);
System.out.println(getChangeListeners(booleanProperty).length);
System.out.println(getChangeListeners(simpleFloatProperty).length);
System.out.println(getChangeListeners(simpleIntegerProperty).length);
the result:
so I do get warnings, but the job is done!
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With