org.rstudio.core.client.WidgetHandlerRegistration.java Source code

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Here is the source code for org.rstudio.core.client.WidgetHandlerRegistration.java

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/*
 * 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_;
}