public abstract class DoubleBinding extends DoubleExpression implements NumberBinding
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 javafx.beans.value.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);
}
};
Binding
,
NumberBinding
,
DoubleExpression
Modifier and Type | Field and Description |
---|---|
private <any> |
helper |
private BindingHelperObserver |
observer |
private boolean |
valid |
private double |
value |
Constructor and Description |
---|
DoubleBinding() |
Modifier and Type | Method and Description |
---|---|
void |
addListener(<any> listener) |
void |
addListener(InvalidationListener listener) |
protected void |
bind(Observable... dependencies)
Start observing the dependencies for changes.
|
protected abstract double |
computeValue()
Calculates the current value of this binding.
|
void |
dispose()
A default implementation of
dispose() that is empty. |
double |
get()
Returns the result of
computeValue() . |
<any> |
getDependencies()
A default implementation of
getDependencies() that returns an
empty javafx.collections.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(<any> listener) |
void |
removeListener(InvalidationListener listener) |
java.lang.String |
toString()
Returns a string representation of this
DoubleBinding object. |
protected void |
unbind(Observable... dependencies)
Stop observing the dependencies for changes.
|
add, asObject, divide, doubleExpression, doubleExpression, doubleValue, floatValue, getValue, intValue, longValue, multiply, negate, subtract
asString, asString, asString, greaterThan, greaterThanOrEqualTo, isEqualTo, isEqualTo, isNotEqualTo, isNotEqualTo, lessThan, lessThanOrEqualTo, numberExpression
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
add, asString, asString, asString, divide, greaterThan, greaterThanOrEqualTo, isEqualTo, isEqualTo, isNotEqualTo, isNotEqualTo, lessThan, lessThanOrEqualTo, multiply, negate, subtract
private double value
private boolean valid
private BindingHelperObserver observer
private <any> helper
public void addListener(InvalidationListener listener)
public void removeListener(InvalidationListener listener)
public void addListener(<any> listener)
public void removeListener(<any> listener)
protected final void bind(Observable... dependencies)
dependencies
- the dependencies to observeprotected final void unbind(Observable... dependencies)
dependencies
- the dependencies to stop observingpublic void dispose()
dispose()
that is empty.public <any> getDependencies()
getDependencies()
that returns an
empty javafx.collections.ObservableList
.getDependencies
in interface Binding<java.lang.Number>
ObservableList
public final double get()
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()
.protected void onInvalidating()
public final void invalidate()
Binding
Binding
next time it is request.invalidate
in interface Binding<java.lang.Number>
public final boolean isValid()
Binding
protected abstract double computeValue()
Classes extending DoubleBinding
have to provide an implementation
of computeValue
.
public java.lang.String toString()
DoubleBinding
object.toString
in class java.lang.Object
DoubleBinding
object.