/*******************************************************************************
* Copyright 2013 Geoscience Australia
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
******************************************************************************/
package au.gov.ga.earthsci.common.databinding;
import java.util.HashMap;
import java.util.Map;
import org.eclipse.core.databinding.observable.list.IListChangeListener;
import org.eclipse.core.databinding.observable.list.IObservableList;
import org.eclipse.core.databinding.observable.list.ListChangeEvent;
import org.eclipse.core.databinding.observable.list.ListDiffEntry;
import org.eclipse.core.databinding.observable.masterdetail.IObservableFactory;
/**
* Class that observes a list property of an input, using an
* {@link IObservableFactory} to create the observer. Also recusively observes
* the list property of each of the input's list elements, and each of those
* element's list elements, and so on.
* <p/>
* User can register {@link ITreeChangeListener}s to listen for changes to the
* tree data structure.
*
* @author Michael de Hoog (michael.dehoog@ga.gov.au)
*/
public class ObservableListTreeSupport<E>
{
private TreeChangeListenerList<E> listeners = new TreeChangeListenerList<E>();
private final Map<E, IObservableList<E>> elementToObservable = new HashMap<E, IObservableList<E>>();
private final IObservableFactory<E, IObservableList<E>> observableFactory;
private E input;
/**
* Constructor.
*
* @param observableFactory
* Factory that creates observers on a list property of
* <code>E</code>.
*/
public ObservableListTreeSupport(final IObservableFactory<E, IObservableList<E>> observableFactory)
{
this.observableFactory = observableFactory;
}
/**
* Removes all observers from the input. Calls {@link #setInput(Object)}
* with a <code>null</code> argument.
*/
public void dispose()
{
setInput(null);
}
/**
* @return The root object being observed.
*/
public E getInput()
{
return input;
}
/**
* Set the root object to observe.
* <p/>
* All observers are removed from any previous input and its children, and
* the listeners are notified of the removals with
* {@link ITreeChangeListener#elementRemoved(Object)}.
* <p/>
* Observers are then added to the new input and any children, and the
* listeners are notified of the adds with
* {@link ITreeChangeListener#elementAdded(Object)}.
* <p/>
* Passing a <code>null</code> input means that all listens are removed from
* the previous input.
*
* @param input
* Input to observe
*/
public void setInput(E input)
{
if (this.input == input)
{
return;
}
if (this.input != null)
{
removed(this.input);
}
this.input = input;
if (this.input != null)
{
added(this.input);
}
}
/**
* Add a listener to listen to structural changes to the observed input
* hierarchy.
*
* @param listener
* Listener to add
*/
public void addListener(ITreeChangeListener<E> listener)
{
listeners.add(listener);
}
/**
* Remove an added listener.
*
* @param listener
* Listener to remove
*/
public void removeListener(ITreeChangeListener<E> listener)
{
listeners.remove(listener);
}
private void added(E input)
{
listeners.elementAdded(input);
IObservableList<E> observable = observableFactory.createObservable(input);
elementToObservable.put(input, observable);
observable.addListChangeListener(listChangeListener);
for (E element : observable)
{
added(element);
}
}
private void removed(E input)
{
listeners.elementRemoved(input);
IObservableList<E> observable = elementToObservable.remove(input);
if (observable != null)
{
observable.removeListChangeListener(listChangeListener);
for (E element : observable)
{
removed(element);
}
observable.dispose();
}
}
private final IListChangeListener<E> listChangeListener = new IListChangeListener<E>()
{
@Override
public void handleListChange(ListChangeEvent<E> event)
{
for (ListDiffEntry<? extends E> entry : event.diff.getDifferencesAsList())
{
E element = entry.getElement();
if (entry.isAddition())
{
added(element);
}
else
{
removed(element);
}
}
}
};
}