org.jboss.errai.common.client.ui.ValueChangeManager.java Source code

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Here is the source code for org.jboss.errai.common.client.ui.ValueChangeManager.java

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/**
 * Copyright (C) 2016 Red Hat, Inc. and/or its affiliates.
 *
 * 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 org.jboss.errai.common.client.ui;

import com.google.gwt.event.dom.client.ChangeEvent;
import com.google.gwt.event.dom.client.ChangeHandler;
import com.google.gwt.event.logical.shared.HasValueChangeHandlers;
import com.google.gwt.event.logical.shared.ValueChangeEvent;
import com.google.gwt.event.logical.shared.ValueChangeHandler;
import com.google.gwt.event.shared.GwtEvent;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.user.client.ui.HasValue;
import com.google.gwt.user.client.ui.Widget;

/**
 * Utility class for managing widgets implementing {@link HasValue}.
 *
 * @author Max Barkley <mbarkley@redhat.com>
 */
public class ValueChangeManager<T, W extends Widget & HasValue<T>> implements HasValueChangeHandlers<T> {

    private boolean valueChangeHandlerInitialized;
    private final W widget;

    public ValueChangeManager(final W widget) {
        this.widget = widget;
    }

    @Override
    public void fireEvent(final GwtEvent<?> event) {
        widget.fireEvent(event);
    }

    @Override
    public HandlerRegistration addValueChangeHandler(final ValueChangeHandler<T> handler) {
        if (!valueChangeHandlerInitialized) {
            valueChangeHandlerInitialized = true;
            widget.addDomHandler(new ChangeHandler() {
                @Override
                public void onChange(ChangeEvent event) {
                    ValueChangeEvent.fire(widget, widget.getValue());
                }
            }, ChangeEvent.getType());
        }
        return widget.addHandler(handler, ValueChangeEvent.getType());
    }

}