Module javafx.base

Package javafx.beans.binding

Class BooleanBinding

java.lang.Object

javafx.beans.binding.BooleanExpression

javafx.beans.binding.BooleanBinding

All Implemented Interfaces:

Binding<Boolean>, Observable, ObservableBooleanValue, ObservableValue<Boolean>

public abstract class BooleanBinding
extends BooleanExpression
implements Binding<Boolean>

Base class that provides most of the functionality needed to implement a Binding of a boolean value.

BooleanBinding provides a simple invalidation-scheme. An extending class can register dependencies by calling bind(Observable...). If One of the registered dependencies becomes invalid, this BooleanBinding 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, BooleanExpression

Constructor Summary

Constructors

Constructor	Description
BooleanBinding()	Sole constructor

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 Boolean> listener)	Adds a ChangeListener which will be notified whenever the value of the ObservableValue changes.
protected void	bind(Observable... dependencies)	Start observing the dependencies for changes.
protected abstract boolean	computeValue()	Calculates the current value of this binding.
void	dispose()	A default implementation of dispose() that is empty.
boolean	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(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 Boolean> 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 BooleanBinding object.
protected void	unbind(Observable... dependencies)	Stop observing the dependencies for changes.

Methods inherited from class javafx.beans.binding.BooleanExpression

and, asObject, asString, booleanExpression, booleanExpression, getValue, isEqualTo, isNotEqualTo, not, or

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

Constructor Detail

BooleanBinding

public BooleanBinding()

Sole constructor

Method Detail

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:

Observable.removeListener(InvalidationListener)

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:

Observable.addListener(InvalidationListener)

addListener

public void addListener(ChangeListener<? super Boolean> 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<Boolean>

Parameters:

listener - The listener to register

See Also:

ObservableValue.removeListener(ChangeListener)

removeListener

public void removeListener(ChangeListener<? super Boolean> 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.

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 ObservableValue<Boolean>

Parameters:

listener - The listener to remove

See Also:

ObservableValue.addListener(ChangeListener)

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<Boolean>

getDependencies

public ObservableList<?> getDependencies()

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

Specified by:

getDependencies in interface Binding<Boolean>

Returns:

an empty ObservableList

get

public final boolean 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 ObservableBooleanValue

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 the Binding next time it is request.

Specified by:

invalidate in interface Binding<Boolean>

isValid

public final boolean isValid()

Description copied from interface: Binding

Checks if a binding is valid.

Specified by:

isValid in interface Binding<Boolean>

Returns:

true if the Binding is valid, false otherwise

computeValue

protected abstract boolean computeValue()

Calculates the current value of this binding.

Classes extending BooleanBinding have to provide an implementation of computeValue.

Returns:

the current value

toString

public String toString()

Returns a string representation of this BooleanBinding object.

Overrides:

toString in class Object

Returns:

a string representation of this BooleanBinding object.