/*
* WidgetHandlerRegistration.java
*
* Copyright (C) 2009-12 by RStudio, Inc.
*
* Unless you have received this program directly from RStudio pursuant
* to the terms of a commercial license agreement with RStudio, then
* this program is licensed to you under the terms of version 3 of the
* GNU Affero General Public License. This program is distributed WITHOUT
* ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING THOSE OF NON-INFRINGEMENT,
* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Please refer to the
* AGPL (http://www.gnu.org/licenses/agpl-3.0.txt) for more details.
*
*/
package org.rstudio.core.client;
import com.google.gwt.event.logical.shared.AttachEvent;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.user.client.ui.Widget;
/**
* Automatically registers and unregisters a handler as a widget
* becomes attached and detached from the DOM.
*
* To use, create a concrete subclass and override the doRegister
* method to do the actual addHandler call.
*/
public abstract class WidgetHandlerRegistration
{
public WidgetHandlerRegistration(Widget widget)
{
widget.addAttachHandler(new AttachEvent.Handler()
{
@Override
public void onAttachOrDetach(AttachEvent event)
{
unregister();
if (event.isAttached())
register();
}
});
if (widget.isAttached())
register();
}
public void register()
{
registration_ = doRegister();
}
protected abstract HandlerRegistration doRegister();
private void unregister()
{
if (registration_ != null)
{
registration_.removeHandler();
registration_ = null;
}
}
private HandlerRegistration registration_;
}