Top Description Fields Constructors Methods
javafx.beans.binding

public abstract Class ObjectBinding<T>

extends ObjectExpression<T>
implements Binding<T>
Class Inheritance
All Implemented Interfaces
javafx.beans.binding.Binding, javafx.beans.value.ObservableValue, javafx.beans.Observable
Known Direct Subclasses
javafx.beans.binding.When.ObjectCondition, com.sun.javafx.binding.LazyObjectBinding, com.sun.javafx.binding.SelectBinding.AsObject
Type Parameters
<T>
the type of the wrapped Object
Imports
javafx.beans.InvalidationListener, .Observable, javafx.beans.value.ChangeListener, javafx.collections.FXCollections, .ObservableList, com.sun.javafx.binding.BindingHelperObserver, .ExpressionHelper
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
Binding, javafx.beans.binding.ObjectExpression

Field Summary

Modifier and TypeField and Description
private ExpressionHelper<T>
helper

private boolean
observed

private BindingHelperObserver
observer

Invalidation listener used for observing dependencies.

private boolean
valid

private T
value

Constructor Summary

AccessConstructor and Description
public
ObjectBinding()

Creates a default ObjectBinding.

Method Summary

Modifier and TypeMethod and Description
public void
addListener(InvalidationListener
The listener to register
listener)

Implements javafx.beans.Observable.addListener.

Adds an InvalidationListener which will be notified whenever the Observable becomes invalid.

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

Implements javafx.beans.value.ObservableValue.addListener.

Adds a ChangeListener which will be notified whenever the value of the ObservableValue changes.

protected boolean

Returns:

true if this binding is allowed to become valid, otherwise false
allowValidation()

Checks if the binding is allowed to become valid.

protected final void
bind(Observable...
the dependencies to observe
dependencies)

Start observing the dependencies for changes.

protected abstract T

Returns:

the current value
computeValue()

Calculates the current value of this binding.

public void
dispose()

Implements javafx.beans.binding.Binding.dispose.

A default implementation of dispose() that is empty.

public final T

Returns:

the current value
get()

Implements javafx.beans.value.ObservableObjectValue.get.

Returns the result of computeValue().

public ObservableList<?>

Returns:

an empty ObservableList
getDependencies()

Implements javafx.beans.binding.Binding.getDependencies.

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

public final void
invalidate()

Implements javafx.beans.binding.Binding.invalidate.

Mark a binding as invalid.

protected final boolean

Returns:

true if this binding currently has one or more listeners registered on it, otherwise false
isObserved()

Checks if the binding has at least one listener registered on it.

public final boolean
isValid()

Implements javafx.beans.binding.Binding.isValid.

Checks if a binding is valid.

protected void
onInvalidating()

Called when this binding becomes invalid.

public void
removeListener(InvalidationListener
The listener to remove
listener)

Implements javafx.beans.Observable.removeListener.

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

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

Implements javafx.beans.value.ObservableValue.removeListener.

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

public String

Returns:

a string representation of this ObjectBinding object.
toString()

Overrides java.lang.Object.toString.

Returns a string representation of this ObjectBinding object.

protected final void
unbind(Observable...
the dependencies to stop observing
dependencies)

Stop observing the dependencies for changes.

Inherited from javafx.beans.binding.ObjectExpression:
asStringasStringasStringgetValueisEqualToisEqualToisNotEqualToisNotEqualToisNotNullisNullobjectExpression

Field Detail

helperback to summary
private ExpressionHelper<T> helper
observedback to summary
private boolean observed
observerback to summary
private BindingHelperObserver observer

Invalidation listener used for observing dependencies. This is never cleared once created as there is no way to determine when all dependencies that were previously bound were removed in one or more calls to unbind(Observable...).

validback to summary
private boolean valid
valueback to summary
private T value

Constructor Detail

ObjectBindingback to summary
public ObjectBinding()

Creates a default ObjectBinding.

Method Detail

addListenerback to summary
public void addListener(InvalidationListener listener)

Implements javafx.beans.Observable.addListener.

Doc from javafx.beans.Observable.addListener.

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.

Parameters
listener:InvalidationListener

The listener to register

Annotations
@Override
addListenerback to summary
public void addListener(ChangeListener<? super T> listener)

Implements javafx.beans.value.ObservableValue.addListener.

Doc from javafx.beans.value.ObservableValue.addListener.

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.

Parameters
listener:ChangeListener<? super T>

The listener to register

Annotations
@Override
allowValidationback to summary
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:boolean

true if this binding is allowed to become valid, otherwise false

Since
19
bindback to summary
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:Observable[]

the dependencies to observe

computeValueback to summary
protected abstract T computeValue()

Calculates the current value of this binding.

Classes extending ObjectBinding have to provide an implementation of computeValue.

Returns:T

the current value

disposeback to summary
public void dispose()

Implements javafx.beans.binding.Binding.dispose.

A default implementation of dispose() that is empty.

Annotations
@Override
getback to summary
public final T get()

Implements javafx.beans.value.ObservableObjectValue.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().

Returns:T

the current value

Annotations
@Override
getDependenciesback to summary
public ObservableList<?> getDependencies()

Implements javafx.beans.binding.Binding.getDependencies.

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

Returns:ObservableList<?>

an empty ObservableList

Annotations
@Override
invalidateback to summary
public final void invalidate()

Implements javafx.beans.binding.Binding.invalidate.

Doc from javafx.beans.binding.Binding.invalidate.

Mark a binding as invalid. This forces the recalculation of the value of the Binding next time it is request.

Annotations
@Override
isObservedback to summary
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:boolean

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

Since
19
isValidback to summary
public final boolean isValid()

Implements javafx.beans.binding.Binding.isValid.

Doc from javafx.beans.binding.Binding.isValid.

Checks if a binding is valid.

Returns:boolean

true if the Binding is valid, false otherwise

Annotations
@Override
onInvalidatingback to summary
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.

removeListenerback to summary
public void removeListener(InvalidationListener listener)

Implements javafx.beans.Observable.removeListener.

Doc from javafx.beans.Observable.removeListener.

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.

Parameters
listener:InvalidationListener

The listener to remove

Annotations
@Override
removeListenerback to summary
public void removeListener(ChangeListener<? super T> listener)

Implements javafx.beans.value.ObservableValue.removeListener.

Doc from javafx.beans.value.ObservableValue.removeListener.

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.

Parameters
listener:ChangeListener<? super T>

The listener to remove

Annotations
@Override
toStringback to summary
public String toString()

Overrides java.lang.Object.toString.

Returns a string representation of this ObjectBinding object.

Returns:String

a string representation of this ObjectBinding object.

Annotations
@Override
unbindback to summary
protected final void unbind(Observable... dependencies)

Stop observing the dependencies for changes.

Parameters
dependencies:Observable[]

the dependencies to stop observing