org.jrydberg.bindings.client.AbstractBinding.java Source code

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Here is the source code for org.jrydberg.bindings.client.AbstractBinding.java

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/**
 * Copyright 2010 Johan Rydberg
 *
 * 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.jrydberg.bindings.client;

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

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.HandlerManager;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.user.client.ui.HasValue;

/**
 * @author jrydberg
 * 
 */
public class AbstractBinding<S, T> implements Property<T>, PropertyChangeListener {

    private final HandlerManager handlerManager = new HandlerManager(this);

    private HasValue<S> sourceBox;

    private S cachedSource;

    private T cachedValue;

    private HandlerRegistration handlerRegistration;

    private final ValueChangeHandler<S> valueChangeHandler = new ValueChangeHandler<S>() {
        public void onValueChange(ValueChangeEvent<S> event) {
            onSourceChange(true);
        }
    };

    public AbstractBinding(HasValue<S> sourceBox) {
        setSourceBox(sourceBox);
    }

    protected S getSource() {
        return cachedSource;
    }

    protected void setSource(S source) {
        this.cachedSource = source;
    }

    protected String getPropertyName() {
        return null;
    }

    protected void setSourceBox(HasValue<S> sourceBox) {
        if (this.sourceBox != sourceBox) {
            if (this.sourceBox != null) {
                handlerRegistration.removeHandler();
            }
            this.sourceBox = sourceBox;
            if (sourceBox != null) {
                handlerRegistration = sourceBox.addValueChangeHandler(valueChangeHandler);
                onSourceChange(false);
            }
        }
    }

    HandlerRegistration propertyHandler;

    private void onSourceChange(boolean fireEvents) {
        S oldCachedSource = cachedSource;
        cachedSource = sourceBox.getValue();

        if (oldCachedSource != cachedSource) {
            if (getPropertyName() != null) {
                if (oldCachedSource instanceof HasProperties) {
                    ((HasProperties) oldCachedSource).removePropertyChangeListener(getPropertyName(), this);
                }
                if (cachedSource instanceof HasProperties) {
                    ((HasProperties) cachedSource).addPropertyChangeListener(getPropertyName(), this);
                }
            }
        }

        T oldCachedValue = cachedValue;
        cachedValue = this.getValue();
        if (cachedValue != oldCachedValue && fireEvents) {
            ValueChangeEvent.fire(this, cachedValue);
        }
    }

    @Override
    public void propertyChange(PropertyChangeEvent event) {
        onSourceChange(true);
    }

    /*
     * (non-Javadoc)
     * 
     * @see com.google.gwt.user.client.ui.HasValue#setValue(java.lang.Object,
     * boolean)
     */
    @Override
    public void setValue(T value, boolean fireEvents) {
        this.setValue(value);
        if (fireEvents) {
            ValueChangeEvent.fire(this, value);
        }
    }

    /*
     * (non-Javadoc)
     * 
     * @seecom.google.gwt.event.logical.shared.HasValueChangeHandlers#
     * addValueChangeHandler
     * (com.google.gwt.event.logical.shared.ValueChangeHandler)
     */
    @Override
    public HandlerRegistration addValueChangeHandler(ValueChangeHandler<T> handler) {
        return handlerManager.addHandler(ValueChangeEvent.getType(), handler);
    }

    /*
     * (non-Javadoc)
     * 
     * @see
     * com.google.gwt.event.shared.HasHandlers#fireEvent(com.google.gwt.event.
     * shared.GwtEvent)
     */
    @Override
    public void fireEvent(GwtEvent<?> event) {
        handlerManager.fireEvent(event);
    }

    /*
     * (non-Javadoc)
     * 
     * @see com.google.gwt.user.client.ui.HasValue#getValue()
     */
    @Override
    public T getValue() {
        // TODO Auto-generated method stub
        return null;
    }

    /*
     * (non-Javadoc)
     * 
     * @see com.google.gwt.user.client.ui.HasValue#setValue(java.lang.Object)
     */
    @Override
    public void setValue(T value) {
        // TODO Auto-generated method stub

    }

}