- Type Parameters:
T
- the type of the wrappedObject
- All Implemented Interfaces:
Binding<T>
,Observable
,ObservableObjectValue<T>
,ObservableValue<T>
public abstract class ObjectBinding<T> extends ObjectExpression<T> implements Binding<T>
Binding
of an Object
.
ObjectBinding
provides a simple invalidation-scheme. An extending
class can register dependencies by calling bind(Observable...)
.
If One of the registered dependencies becomes invalid, this
ObjectBinding
is marked as invalid. With
unbind(Observable...)
listening to dependencies can be stopped.
To provide a concrete implementation of this class, the method
computeValue()
has to be implemented to calculate the value of this
binding based on the current state of the dependencies. It is called when
get()
is called for an invalid binding.
See DoubleBinding
for an example how this base class can be extended.
- Since:
- JavaFX 2.0
- See Also:
Binding
,ObjectExpression
-
Constructor Summary
Constructors Constructor Description ObjectBinding()
Creates a defaultObjectBinding
. -
Method Summary
Modifier and Type Method Description void
addListener(InvalidationListener listener)
Adds anInvalidationListener
which will be notified whenever theObservable
becomes invalid.void
addListener(ChangeListener<? super T> listener)
Adds aChangeListener
which will be notified whenever the value of theObservableValue
changes.protected void
bind(Observable... dependencies)
Start observing the dependencies for changes.protected abstract T
computeValue()
Calculates the current value of this binding.void
dispose()
A default implementation ofdispose()
that is empty.T
get()
Returns the result ofcomputeValue()
.ObservableList<?>
getDependencies()
A default implementation ofgetDependencies()
that returns an emptyObservableList
.void
invalidate()
Mark a binding as invalid.boolean
isValid()
Checks if a binding is valid.protected void
onInvalidating()
The method onInvalidating() can be overridden by extending classes to react, if this binding becomes invalid.void
removeListener(InvalidationListener listener)
Removes the given listener from the list of listeners, that are notified whenever the value of theObservable
becomes invalid.void
removeListener(ChangeListener<? super T> listener)
Removes the given listener from the list of listeners that are notified whenever the value of theObservableValue
changes.String
toString()
Returns a string representation of thisObjectBinding
object.protected void
unbind(Observable... dependencies)
Stop observing the dependencies for changes.Methods inherited from class javafx.beans.binding.ObjectExpression
asString, asString, asString, getValue, isEqualTo, isEqualTo, isNotEqualTo, isNotEqualTo, isNotNull, isNull, objectExpression
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods inherited from interface javafx.beans.value.ObservableValue
getValue
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Constructor Details
-
ObjectBinding
public ObjectBinding()Creates a defaultObjectBinding
.
-
-
Method Details
-
addListener
Description copied from interface:Observable
Adds anInvalidationListener
which will be notified whenever theObservable
becomes invalid. If the same listener is added more than once, then it will be notified more than once. That is, no check is made to ensure uniqueness.Note that the same actual
InvalidationListener
instance may be safely registered for differentObservables
.The
Observable
stores a strong reference to the listener which will prevent the listener from being garbage collected and may result in a memory leak. It is recommended to either unregister a listener by callingremoveListener
after use or to use an instance ofWeakInvalidationListener
avoid this situation.- Specified by:
addListener
in interfaceObservable
- Parameters:
listener
- The listener to register- See Also:
Observable.removeListener(InvalidationListener)
-
removeListener
Description copied from interface:Observable
Removes the given listener from the list of listeners, that are notified whenever the value of theObservable
becomes invalid.If the given listener has not been previously registered (i.e. it was never added) then this method call is a no-op. If it had been previously added then it will be removed. If it had been added more than once, then only the first occurrence will be removed.
- Specified by:
removeListener
in interfaceObservable
- Parameters:
listener
- The listener to remove- See Also:
Observable.addListener(InvalidationListener)
-
addListener
Description copied from interface:ObservableValue
Adds aChangeListener
which will be notified whenever the value of theObservableValue
changes. If the same listener is added more than once, then it will be notified more than once. That is, no check is made to ensure uniqueness.Note that the same actual
ChangeListener
instance may be safely registered for differentObservableValues
.The
ObservableValue
stores a strong reference to the listener which will prevent the listener from being garbage collected and may result in a memory leak. It is recommended to either unregister a listener by callingremoveListener
after use or to use an instance ofWeakChangeListener
avoid this situation.- Specified by:
addListener
in interfaceObservableValue<T>
- Parameters:
listener
- The listener to register- See Also:
ObservableValue.removeListener(ChangeListener)
-
removeListener
Description copied from interface:ObservableValue
Removes the given listener from the list of listeners that are notified whenever the value of theObservableValue
changes.If the given listener has not been previously registered (i.e. it was never added) then this method call is a no-op. If it had been previously added then it will be removed. If it had been added more than once, then only the first occurrence will be removed.
- Specified by:
removeListener
in interfaceObservableValue<T>
- Parameters:
listener
- The listener to remove- See Also:
ObservableValue.addListener(ChangeListener)
-
bind
Start observing the dependencies for changes. If the value of one of the dependencies changes, the binding is marked as invalid.- Parameters:
dependencies
- the dependencies to observe
-
unbind
Stop observing the dependencies for changes.- Parameters:
dependencies
- the dependencies to stop observing
-
dispose
public void dispose()A default implementation ofdispose()
that is empty. -
getDependencies
A default implementation ofgetDependencies()
that returns an emptyObservableList
.- Specified by:
getDependencies
in interfaceBinding<T>
- Returns:
- an empty
ObservableList
-
get
Returns the result ofcomputeValue()
. The methodcomputeValue()
is only called if the binding is invalid. The result is cached and returned if the binding did not become invalid since the last call ofget()
.- Specified by:
get
in interfaceObservableObjectValue<T>
- Returns:
- the current value
-
onInvalidating
protected void onInvalidating()The method onInvalidating() can be overridden by extending classes to react, if this binding becomes invalid. The default implementation is empty. -
invalidate
public final void invalidate()Description copied from interface:Binding
Mark a binding as invalid. This forces the recalculation of the value of theBinding
next time it is request.- Specified by:
invalidate
in interfaceBinding<T>
-
isValid
public final boolean isValid()Description copied from interface:Binding
Checks if a binding is valid. -
computeValue
Calculates the current value of this binding.Classes extending
ObjectBinding
have to provide an implementation ofcomputeValue
.- Returns:
- the current value
-
toString
Returns a string representation of thisObjectBinding
object.
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