Class ObjectBinding<T>

java.lang.Object

javafx.beans.binding.ObjectExpression<T>

javafx.beans.binding.ObjectBinding<T>

Type Parameters:: T - the type of the wrapped Object

All Implemented Interfaces:: Binding<T>, Observable, ObservableObjectValue<T>, ObservableValue<T>

public abstract class ObjectBinding<T> extends ObjectExpression<T> implements Binding<T>

Base class that provides most of the functionality needed to implement a 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:

Constructor Summary

Constructor	Description
`ObjectBinding()`	Creates a default `ObjectBinding`.

Method Summary

Modifier and Type	Method	Description
`void`	`addListener(InvalidationListener listener)`	Adds an `InvalidationListener` which will be notified whenever the `Observable` becomes invalid.
`void`	`addListener(ChangeListener<? super T> listener)`	Adds a `ChangeListener` which will be notified whenever the value of the `ObservableValue` changes.
`protected boolean`	`allowValidation()`	Checks if the binding is allowed to become valid.
`protected final 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.
`final T`	`get()`	Returns the result of `computeValue()`.
`ObservableList<?>`	`getDependencies()`	A default implementation of `getDependencies()` that returns an empty `ObservableList`.
`final void`	`invalidate()`	Mark a binding as invalid.
`protected final boolean`	`isObserved()`	Checks if the binding has at least one listener registered on it.
`final boolean`	`isValid()`	Checks if a binding is valid.
`protected void`	`onInvalidating()`	Called when this binding becomes invalid.
`void`	`removeListener(InvalidationListener listener)`	Removes the given listener from the list of listeners, that are notified whenever the value of the `Observable` 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.
`String`	`toString()`	Returns a string representation of this `ObjectBinding` object.
`protected final void`	`unbind(Observable... dependencies)`	Stop observing the dependencies for changes.

Methods declared in class javafx.beans.binding.ObjectExpression

asString, asString, asString, getValue, isEqualTo, isEqualTo, isNotEqualTo, isNotEqualTo, isNotNull, isNull, objectExpression

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods declared in interface javafx.beans.Observable

subscribe

Methods declared in interface javafx.beans.value.ObservableValue

flatMap, getValue, map, orElse, subscribe, subscribe, when

Constructor Details

ObjectBinding

public ObjectBinding()

Creates a default ObjectBinding.

Method Details

addListener

public void addListener(InvalidationListener listener)

Description copied from interface: Observable

Adds an 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.

Specified by:

addListener in interface Observable

Parameters:

listener - The listener to register

See Also:

removeListener

public void removeListener(InvalidationListener listener)

Description copied from interface: Observable

Removes the given listener from the list of listeners, that are notified whenever the value of the 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.

Specified by:

removeListener in interface Observable

Parameters:

listener - The listener to remove

See Also:

addListener

public void addListener(ChangeListener<? super T> listener)

Description copied from interface: ObservableValue

Adds a 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.

Specified by:

addListener in interface ObservableValue<T>

Parameters:

listener - The listener to register

See Also:

removeListener

public void removeListener(ChangeListener<? super T> listener)

Description copied from interface: ObservableValue

Removes the given listener from the list of listeners that are notified whenever the value of the ObservableValue changes.

Specified by:

removeListener in interface ObservableValue<T>

Parameters:

listener - The listener to remove

See Also:

bind

protected final void bind(Observable... dependencies)

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

protected final void unbind(Observable... dependencies)

Stop observing the dependencies for changes.

Parameters:: dependencies - the dependencies to stop observing

dispose

public void dispose()

A default implementation of dispose() that is empty.

Specified by:: dispose in interface Binding<T>

getDependencies

public ObservableList<?> getDependencies()

A default implementation of getDependencies() that returns an empty ObservableList.

Specified by:: getDependencies in interface Binding<T>
Returns:: an empty ObservableList

get

public final T get()

Returns the result of 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().

Specified by:: get in interface ObservableObjectValue<T>
Returns:: the current value

onInvalidating

protected void onInvalidating()

Called when this binding becomes invalid. Can be overridden by extending classes to react to the invalidation. 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 the Binding next time it is request.

Specified by:: invalidate in interface Binding<T>

isValid

public final boolean isValid()

Description copied from interface: Binding

Checks if a binding is valid.

Specified by:: isValid in interface Binding<T>
Returns:: true if the Binding is valid, false otherwise

isObserved

protected final boolean isObserved()

Checks if the binding has at least one listener registered on it. This is useful for subclasses which want to conserve resources when not observed.

Returns:: true if this binding currently has one or more listeners registered on it, otherwise false
Since:: 19

allowValidation

protected boolean allowValidation()

Checks if the binding is allowed to become valid. Overriding classes can prevent a binding from becoming valid. This is useful in subclasses which do not always listen for invalidations of their dependencies and prefer to recompute the current value instead. This can also be useful if caching of the current computed value is not desirable.

The default implementation always allows bindings to become valid.

Returns:: true if this binding is allowed to become valid, otherwise false
Since:: 19

computeValue

protected abstract T computeValue()

Calculates the current value of this binding.

Classes extending ObjectBinding have to provide an implementation of computeValue.

Returns:: the current value

toString

public String toString()

Returns a string representation of this ObjectBinding object.

Overrides:: toString in class Object
Returns:: a string representation of this ObjectBinding object.

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Documentation extracted from JavaFX API Documentation.
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