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java.lang.Objectjava.beans.PropertyChangeSupport
com.jgoodies.binding.beans.ExtendedPropertyChangeSupport
public final class ExtendedPropertyChangeSupport
Differs from its superclass PropertyChangeSupport
in that it can
check for changed values using #equals
or ==
.
Useful if you want to ensure that a PropertyChangeEvent
is fired
if the old and new value are not the same but if they are equal.
The Java Bean Specification recommends to not throw a PropertyChangeEvent if the old and new value of a bound Bean property are equal (see chapter 7.4.4). This can reduce the number of events fired and helps avoid loops. Nevertheless a bound property may fire an event if the old and new value are equal.
An example for a condition where the identity check ==
is required and the #equals
test fails is class
SelectionInList
. If the contained
ListModel
changes its value, an internal listener is removed
from the old value and added to the new value. The listener must be
moved from the old instance to the new instance even if these are equal.
The PropertyChangeSupport
doesn't fire a property change event
if such a ListModel
is implemented as a List
.
This is because instances of List
are equal if and only if
all list members are equal and if they are in the same sequence.
This class provides two means to fire an event if the old and new
value are equal but not the same. First, you enable the identity check
in constructor ExtendedPropertyChangeSupport(Object, boolean)
.
By default all calls to #firePropertyChange
will then
check the identity, not the equality. Second, you can invoke
firePropertyChange(PropertyChangeEvent, boolean)
or
firePropertyChange(String, Object, Object, boolean)
and
enable or disable the identity check for this call only.
TODO: (Issue #5) Use WeakReferences to refer to registered listeners.
TODO: (Issue #6) Add an optional check for valid property name when adding a listener for a specific property.
TODO: (Issue #7) Add an optional strict check for existing property names when firing a named property change.
TODO: (Issue #8) Add an option to ensure that update notifications are performed in the event dispatch thread. In case a bean is changed in a thread other than the event dispatch thread, such a feature would help complying with Swing's single thread rule.
TODO: (Issue #11) Consider adding an option that saves update notifications if 'checkIdentity' is true but the value types can be compared safely via #equals, for example Strings, Booleans and Numbers.
PropertyChangeSupport
,
PropertyChangeEvent
,
PropertyChangeListener
,
Object.equals(Object)
,
List.equals(Object)
,
Serialized FormConstructor Summary | |
---|---|
ExtendedPropertyChangeSupport(Object sourceBean)
Constructs an ExtendedPropertyChangeSupport object. |
|
ExtendedPropertyChangeSupport(Object sourceBean,
boolean checkIdentityDefault)
Constructs an ExtendedPropertyChangeSupport object
with the specified default test method for differences between
the old and new property values. |
Method Summary | |
---|---|
void |
firePropertyChange(PropertyChangeEvent evt)
Fires the specified PropertyChangeEvent to any registered listeners. |
void |
firePropertyChange(PropertyChangeEvent evt,
boolean checkIdentity)
Fires an existing PropertyChangeEvent to any registered listeners. |
void |
firePropertyChange(String propertyName,
Object oldValue,
Object newValue)
Reports a bound property update to any registered listeners. |
void |
firePropertyChange(String propertyName,
Object oldValue,
Object newValue,
boolean checkIdentity)
Reports a bound property update to any registered listeners. |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
---|
public ExtendedPropertyChangeSupport(Object sourceBean)
ExtendedPropertyChangeSupport
object.
sourceBean
- The bean to be given as the source for any events.public ExtendedPropertyChangeSupport(Object sourceBean, boolean checkIdentityDefault)
ExtendedPropertyChangeSupport
object
with the specified default test method for differences between
the old and new property values.
sourceBean
- The object provided as the source for any generated events.checkIdentityDefault
- true enables the identity check by defaultMethod Detail |
---|
public void firePropertyChange(PropertyChangeEvent evt)
#equals
vs. ==
)
to determine whether the event's old and new values are different.
No event is fired if old and new value are the same.
firePropertyChange
in class PropertyChangeSupport
evt
- The PropertyChangeEvent object.PropertyChangeSupport.firePropertyChange(PropertyChangeEvent)
public void firePropertyChange(String propertyName, Object oldValue, Object newValue)
#equals
vs. ==
)
to determine whether the event's old and new values are different.
No event is fired if old and new value are the same.
firePropertyChange
in class PropertyChangeSupport
propertyName
- The programmatic name of the property
that was changed.oldValue
- The old value of the property.newValue
- The new value of the property.PropertyChangeSupport.firePropertyChange(String, Object, Object)
public void firePropertyChange(PropertyChangeEvent evt, boolean checkIdentity)
==
or #equals
.
No event is fired if old and new value are the same.
evt
- The PropertyChangeEvent object.checkIdentity
- true to check differences using ==
false to use #equals
.public void firePropertyChange(String propertyName, Object oldValue, Object newValue, boolean checkIdentity)
true
an event is fired in all
other cases. If this parameter is false
, an event is fired
if old and new values are not equal.
propertyName
- The programmatic name of the property
that was changed.oldValue
- The old value of the property.newValue
- The new value of the property.checkIdentity
- true to check differences using ==
false to use #equals
.
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