T
- the type of the wrapped Object
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.
Binding
,
ObjectExpression
Constructor and Description |
---|
ObjectBinding() |
Modifier and Type | Method and Description |
---|---|
void |
addListener(ChangeListener<? super T> listener)
Adds a
ChangeListener which will be notified whenever the value
of the ObservableValue changes. |
void |
addListener(InvalidationListener listener)
Adds an
InvalidationListener which will be notified whenever the
Observable becomes invalid. |
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 of
dispose() that is empty. |
T |
get()
Returns the result of
computeValue() . |
ObservableList<?> |
getDependencies()
A default implementation of
getDependencies() that returns an
empty ObservableList . |
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(ChangeListener<? super T> listener)
Removes the given listener from the list of listeners, that are notified
whenever the value of the
ObservableValue changes. |
void |
removeListener(InvalidationListener listener)
Removes the given listener from the list of listeners, that are notified
whenever the value of the
Observable becomes invalid. |
String |
toString()
Returns a string representation of this
ObjectBinding object. |
protected void |
unbind(Observable... dependencies)
Stop observing the dependencies for changes.
|
asString, asString, asString, getValue, isEqualTo, isEqualTo, isNotEqualTo, isNotEqualTo, isNotNull, isNull, objectExpression
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
getValue
public void addListener(InvalidationListener listener)
Observable
InvalidationListener
which will be notified whenever the
Observable
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 different Observables
.
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 calling removeListener
after use or to use an instance of
WeakInvalidationListener
avoid this situation.
addListener
in interface Observable
listener
- The listener to registerObservable.removeListener(InvalidationListener)
public void removeListener(InvalidationListener listener)
Observable
Observable
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.
removeListener
in interface Observable
listener
- The listener to removeObservable.addListener(InvalidationListener)
public void addListener(ChangeListener<? super T> listener)
ObservableValue
ChangeListener
which will be notified whenever the value
of the ObservableValue
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 different ObservableValues
.
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 calling removeListener
after use or to use an instance of
WeakChangeListener
avoid this situation.
addListener
in interface ObservableValue<T>
listener
- The listener to registerObservableValue.removeListener(ChangeListener)
public void removeListener(ChangeListener<? super T> listener)
ObservableValue
ObservableValue
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.
removeListener
in interface ObservableValue<T>
listener
- The listener to removeObservableValue.addListener(ChangeListener)
protected final void bind(Observable... dependencies)
dependencies
- the dependencies to observeprotected final void unbind(Observable... dependencies)
dependencies
- the dependencies to stop observingpublic void dispose()
dispose()
that is empty.public ObservableList<?> getDependencies()
getDependencies()
that returns an
empty ObservableList
.getDependencies
in interface Binding<T>
ObservableList
public final T get()
computeValue()
. The method
computeValue()
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 of get()
.get
in interface ObservableObjectValue<T>
protected void onInvalidating()
public final void invalidate()
Binding
Binding
next time it is request.invalidate
in interface Binding<T>
public final boolean isValid()
Binding
protected abstract T computeValue()
Classes extending ObjectBinding
have to provide an implementation
of computeValue
.
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