Module javafx.base
Package javafx.beans.binding

Class DoubleBinding

java.lang.Object
javafx.beans.binding.NumberExpressionBase
javafx.beans.binding.DoubleExpression
javafx.beans.binding.DoubleBinding
All Implemented Interfaces:
Binding<Number>, NumberBinding, NumberExpression, Observable, ObservableDoubleValue, ObservableNumberValue, ObservableValue<Number>
public abstract class DoubleBinding
extends DoubleExpression
implements NumberBinding
Base class that provides most of the functionality needed to implement a Binding of a double value.

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

Below is a simple example of a DoubleBinding calculating the square- root of a ObservableNumberValue moo. 

 
 final ObservableDoubleValue moo = ...;

 DoubleBinding foo = new DoubleBinding() {

     {
         super.bind(moo);
     }

     @Override
     protected double computeValue() {
         return Math.sqrt(moo.getValue());
     }
 };
Following is the same example with implementations for the optional methods Binding.getDependencies() and Binding.dispose(). 
 
 final ObservableDoubleValue moo = ...;

 DoubleBinding foo = new DoubleBinding() {

     {
         super.bind(moo);
     }

     @Override
     protected double computeValue() {
         return Math.sqrt(moo.getValue());
     }

     @Override
     public ObservableList<?> getDependencies() {
         return FXCollections.singletonObservableList(moo);
     }

     @Override
     public void dispose() {
         super.unbind(moo);
     }
 };
Since:
JavaFX 2.0
See Also:
Binding, NumberBinding, DoubleExpression

  • Constructor Details

    • DoubleBinding

      public DoubleBinding()
      Creates a default DoubleBinding.

  • Method Details

    • 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<Number>

    • getDependencies

      public ObservableList<?> getDependencies()
      A default implementation of getDependencies() that returns an empty ObservableList.
      Specified by:
      getDependencies in interface Binding<Number>
      Returns:
      an empty ObservableList

    • get

      public final double 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 ObservableDoubleValue
      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.

    • computeValue

      protected abstract double computeValue()
      Calculates the current value of this binding.

      Classes extending DoubleBinding have to provide an implementation of computeValue.

      Returns:
      the current value

    • toString

      public String toString()
      Returns a string representation of this DoubleBinding object.
      Overrides:
      toString in class Object
      Returns:
      a string representation of this DoubleBinding object.