com.jgoodies.binding.list

Class ListModelHolder

Implemented Interfaces:
ListModel, Observable, Serializable
Known Direct Subclasses:
SelectionInListModel

public class ListModelHolder
extends Model
implements ListModel

A ListModel implementation that delegates to a ListModel held by a ValueModel.

Imporant Note: If you change the ListModel instance, either by calling #setListModel(ListModel) or by setting a new value to the underlying list holder, you must ensure that the list holder throws a PropertyChangeEvent whenever the instance changes. This event is used to remove a ListDataListener from the old ListModel instance and is later used to add it to the new ListModel instance. It is easy to violate this constraint, just because Java's standard PropertyChangeSupport helper class that is used by many beans, checks a changed property value via #equals, not ==. For example, if you change the SelectionInList's list model from an empty list L1 to another empty list instance L2, the PropertyChangeSupport won't generate a PropertyChangeEvent, and so, the SelectionInList won't know about the change, which may lead to unexpected behavior.

This class provides public convenience methods for firing ListDataEvents, see the methods #fireContentsChanged, #fireIntervalAdded, and #fireIntervalRemoved. These are automatically invoked if the list holder holds a ListModel that fires these events. If on the other hand the underlying List or ListModel does not fire a required ListDataEvent, you can use these methods to notify presentations about a change. It is recommended to avoid sending duplicate ListDataEvents; hence check if the underlying ListModel fires the necessary events or not. Typically an underlying ListModel will fire the add and remove events; but often it'll lack an event if the (selected) contents has changed.

The current class name "ListModelHolder" and accessor #getListModelHolder may confuse users: what's the difference between the class (a ListModel) and its list model holder (a ValueModel)?

TODO: Find a better name and provide a transition to the new class name. I consider using "IndirectListModel" as the new name.

Version:
$Revision: 1.14 $
Author:
Karsten Lentzsch
Since:
1.1
See Also:
ListHolder, SelectionInListModel

Field Summary

static String
PROPERTYNAME_LIST_MODEL
The name of the bound read-write listModel property.
static String
PROPERTYNAME_LIST_MODEL_HOLDER
The name of the bound read-write listModelHolder property.
protected ListDataListener
listDataChangeHandler
Holds the change handler that fires changes is the ListModel changes.
protected ListModel
listModel
Holds a copy of the listModelHolder's value.

Constructor Summary

ListModelHolder()
Constructs a ListModelHolder with an empty initial ArrayListModel.
ListModelHolder(ListModel listModel)
Constructs a ListModelHolder on the given ListModel.
ListModelHolder(ValueModel listModelHolder)
Constructs a ListModelHolder on the given ListModel.

Method Summary

void
addListDataListener(ListDataListener l)
Adds a listener to the list that's notified each time a change to the data model occurs.
protected ListDataListener
createListDataChangeHandler()
Creates and returns the ListDataListener used to observe changes in the underlying ListModel.
void
fireContentsChanged(int index0, int index1)
Notifies all registered ListDataListeners that the contents of one or more list elements has changed.
void
fireIntervalAdded(int index0, int index1)
Notifies all registered ListDataListeners that one or more elements have been added to this SelectionInList's List/ListModel.
void
fireIntervalRemoved(int index0, int index1)
Notifies all registered ListDataListeners that one or more elements have been removed from this SelectionInList's List/ListModel.
protected void
fireListChanged(int oldLastIndex, int newLastIndex)
Notifies all registered ListDataListeners that this ListModel has changed from an old list to a new list content.
Object
getElementAt(int index)
Returns the value at the specified index.
ListDataListener[]
getListDataListeners()
Returns an array of all the list data listeners registered on this SelectionInList.
ListModel
getListModel()
Returns the contents of the list model holder.
ValueModel
getListModelHolder()
Returns the ValueModel that holds the ListModel we delegate to.
int
getSize()
Returns the length of the list, 0 if the list model is null.
protected int
getSize(ListModel aListOrNull)
Returns the lists size or 0 if the list is null.
boolean
isEmpty()
Checks and answers if the ListModel is empty or null.
void
release()
Removes the internal listener from the list model holder.
void
removeListDataListener(ListDataListener l)
Removes a listener from the list that's notified each time a change to the data model occurs.
void
setListModel(ListModel newListModel)
Sets the given list model as value of the list holder.
void
setListModelHolder(ValueModel newListModelHolder)
Sets a new ListModel holder.
protected void
updateListModel(ListModel oldListModel, ListModel newListModel)
Removes the list data change handler from the old list in case it is not null and adds it to new one in case it is a not null.

Methods inherited from class com.jgoodies.binding.beans.Model

addPropertyChangeListener, addPropertyChangeListener, addVetoableChangeListener, addVetoableChangeListener, equals, fireMultiplePropertiesChanged, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, fireVetoableChange, getPropertyChangeListeners, getPropertyChangeListeners, getVetoableChangeListeners, getVetoableChangeListeners, removePropertyChangeListener, removePropertyChangeListener, removeVetoableChangeListener, removeVetoableChangeListener

Field Details

PROPERTYNAME_LIST_MODEL

public static final String PROPERTYNAME_LIST_MODEL
The name of the bound read-write listModel property.

PROPERTYNAME_LIST_MODEL_HOLDER

public static final String PROPERTYNAME_LIST_MODEL_HOLDER
The name of the bound read-write listModelHolder property.

listDataChangeHandler

protected final ListDataListener listDataChangeHandler
Holds the change handler that fires changes is the ListModel changes.

listModel

protected ListModel listModel
Holds a copy of the listModelHolder's value. Used as the old ListModel when the listModelHolder's value changes. Required because a ValueModel may use null as old value, but this ListModelHolder must know about the old and the new ListModel.

Constructor Details

ListModelHolder

public ListModelHolder()
Constructs a ListModelHolder with an empty initial ArrayListModel.

ListModelHolder

public ListModelHolder(ListModel listModel)
Constructs a ListModelHolder on the given ListModel.
Parameters:
listModel - the initial ListModel

ListModelHolder

public ListModelHolder(ValueModel listModelHolder)
Constructs a ListModelHolder on the given ListModel.

Constraints: 1) The listModelHolder must hold instances of ListModel and 2) must report a value change whenever the value's identity changes. Note that many bean properties don't fire a PropertyChangeEvent if the old and new value are equal - and so would break this constraint. If you provide a ValueHolder, enable its identityCheck feature during construction. If you provide an adapted bean property from a bean that extends the JGoodies Model class, you can enable the identity check feature in the methods #firePropertyChange by setting the trailing boolean parameter to true.

Parameters:
listModelHolder - provides the ListModel

Method Details

addListDataListener

public final void addListDataListener(ListDataListener l)
Adds a listener to the list that's notified each time a change to the data model occurs.
Parameters:
l - the ListDataListener to be added

createListDataChangeHandler

protected ListDataListener createListDataChangeHandler()
Creates and returns the ListDataListener used to observe changes in the underlying ListModel. It is re-registered in #updateListModel.
Returns:
the ListDataListener that handles changes in the underlying ListModel

fireContentsChanged

public final void fireContentsChanged(int index0,
                                      int index1)
Notifies all registered ListDataListeners that the contents of one or more list elements has changed. The changed elements are specified by the closed interval index0, index1 -- the end points are included. Note that index0 need not be less than or equal to index1.
Parameters:
index0 - one end of the new interval
index1 - the other end of the new interval
See Also:
ListModel, ListDataListener, ListDataEvent

fireIntervalAdded

public final void fireIntervalAdded(int index0,
                                    int index1)
Notifies all registered ListDataListeners that one or more elements have been added to this SelectionInList's List/ListModel. The new elements are specified by a closed interval index0, index1 -- the end points are included. Note that index0 need not be less than or equal to index1.
Parameters:
index0 - one end of the new interval
index1 - the other end of the new interval
See Also:
ListModel, ListDataListener, ListDataEvent

fireIntervalRemoved

public final void fireIntervalRemoved(int index0,
                                      int index1)
Notifies all registered ListDataListeners that one or more elements have been removed from this SelectionInList's List/ListModel. index0 and index1 are the end points of the interval that's been removed. Note that index0 need not be less than or equal to index1.
Parameters:
index0 - one end of the removed interval, including index0
index1 - the other end of the removed interval, including index1
See Also:
ListModel, ListDataListener, ListDataEvent

fireListChanged

protected final void fireListChanged(int oldLastIndex,
                                     int newLastIndex)
Notifies all registered ListDataListeners that this ListModel has changed from an old list to a new list content. If the old and new list size differ, a remove or add event for the removed or added interval is fired. A content change is reported for the interval common to the old and new list.

This method is invoked by #updateList during the transition from an old List(Model) to a new List(Model).

The order of the events fired ensures that after each event the size described by the ListDataEvents equals the ListModel size.

Parameters:
oldLastIndex - the last index of the old list
newLastIndex - the last index of the new list

getElementAt

public final Object getElementAt(int index)
Returns the value at the specified index.
Parameters:
index - the requested index
Returns:
the value at index

getListDataListeners

public final ListDataListener[] getListDataListeners()
Returns an array of all the list data listeners registered on this SelectionInList.
Returns:
all of this model's ListDataListeners, or an empty array if no list data listeners are currently registered

getListModel

public final ListModel getListModel()
Returns the contents of the list model holder.
Returns:
the contents of the list model holder.

getListModelHolder

public final ValueModel getListModelHolder()
Returns the ValueModel that holds the ListModel we delegate to.
Returns:
the ValueModel that holds the ListModel we delegate to.

getSize

public final int getSize()
Returns the length of the list, 0 if the list model is null.
Returns:
the size of the list, 0 if the list model is null

getSize

protected final int getSize(ListModel aListOrNull)
Returns the lists size or 0 if the list is null.
Parameters:
aListOrNull - a List or null
Returns:
the list's size or 0 if the list is null

isEmpty

public final boolean isEmpty()
Checks and answers if the ListModel is empty or null.
Returns:
true if the ListModel is empty or null, false otherwise

release

public void release()
Removes the internal listener from the list model holder. If the current list model is not null, the internal ListDataListener is removed from the list model. This ListModelHolder must not be used after calling #release.

To avoid memory leaks it is recommended to invoke this method, if the list model holder lives much longer than this ListModelHolder. Instead of releasing the ListModelHolder, you typically make the list holder obsolete by releasing the PresentationModel or BeanAdapter that has created the model before.

As an alternative you may use ValueModels that in turn use event listener lists implemented using WeakReference.

Basically this release method performs the reverse operation performed during the ListModelHolder construction.

Since:
1.2

removeListDataListener

public final void removeListDataListener(ListDataListener l)
Removes a listener from the list that's notified each time a change to the data model occurs.
Parameters:
l - the ListDataListener to be removed

setListModel

public final void setListModel(ListModel newListModel)
Sets the given list model as value of the list holder.
Parameters:
newListModel - the list model to be set as new list content

setListModelHolder

public final void setListModelHolder(ValueModel newListModelHolder)
Sets a new ListModel holder. Does nothing if old and new holder are equal. Removes the list change handler from the old holder and adds it to the new one. The list data change handler is re-registered by invoking #updateListModel.

TODO: Check and verify whether the list data registration update can be performed in one step after the listHolder has been changed - instead of remove the list data change handler, then changing the listHolder, and finally adding the list data change handler.

Parameters:
newListModelHolder - the ListModel holder to be set

updateListModel

protected void updateListModel(ListModel oldListModel,
                               ListModel newListModel)
Removes the list data change handler from the old list in case it is not null and adds it to new one in case it is a not null. Also fires a property change for listModel and a ListModel update event.
Parameters:
oldListModel - the old ListModel
newListModel - the new ListModel

Copyright © 2002-2007 JGoodies Karsten Lentzsch. All Rights Reserved.