javafx.beans.binding.Binding Maven / Gradle / Ivy
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package javafx.beans.binding;
import javafx.beans.value.ObservableValue;
import javafx.collections.ObservableList;
/**
* A {@code Binding} calculates a value that depends on one or more sources. The
* sources are usually called the dependency of a binding. A binding observes
* its dependencies for changes and updates its value automatically.
*
* While a dependency of a binding can be anything, it is almost always an
* implementation of {@link javafx.beans.value.ObservableValue}. {@code Binding}
* implements {@code ObservableValue} allowing to use it in another binding.
* With that one can assemble very complex bindings from simple bindings.
*
* All bindings in the JavaFX runtime are calculated lazily. That means, if
* a dependency changes, the result of a binding is not immediately
* recalculated, but it is marked as invalid. Next time the value of an invalid
* binding is requested, it is recalculated.
*
* It is recommended to use one of the base classes defined in this package
* (e.g. {@link DoubleBinding}) to define a custom binding, because these
* classes already provide most of the needed functionality. See
* {@link DoubleBinding} for an example.
*
* @param the type of the wrapped value
* @see DoubleBinding
*
* @since JavaFX 2.0
*/
public interface Binding extends ObservableValue {
/**
* Checks if a binding is valid.
*
* @return {@code true} if the {@code Binding} is valid, {@code false}
* otherwise
*/
boolean isValid();
/**
* Mark a binding as invalid. This forces the recalculation of the value of
* the {@code Binding} next time it is request.
*/
void invalidate();
/**
* Returns the dependencies of a binding in an unmodifiable
* {@link javafx.collections.ObservableList}. The implementation is
* optional. The main purpose of this method is to support developers during
* development. It allows to explore and monitor dependencies of a binding
* during runtime.
*
* Because this method should not be used in production code, it is
* recommended to implement this functionality as sparse as possible. For
* example if the dependencies do not change, each call can generate a new
* {@code ObservableList}, avoiding the necessity to store the result.
*
* @return an unmodifiable {@code} ObservableList of the dependencies
*/
ObservableList getDependencies();
/**
* Signals to the {@code Binding} that it will not be used anymore and any
* references can be removed. A call of this method usually results in the
* binding stopping to observe its dependencies by unregistering its
* listener(s). The implementation is optional.
*
* All bindings in our implementation use instances of
* {@link javafx.beans.WeakInvalidationListener}, which means usually
* a binding does not need to be disposed. But if you plan to use your
* application in environments that do not support {@code WeakReferences}
* you have to dispose unused {@code Bindings} to avoid memory leaks.
*/
void dispose();
}