org.sakaiproject.sitestats.tool.wicket.components.AjaxLazyLoadFragment.java Source code

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Here is the source code for org.sakaiproject.sitestats.tool.wicket.components.AjaxLazyLoadFragment.java

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/**
 * $URL$
 * $Id$
 *
 * Copyright (c) 2006-2009 The Sakai Foundation
 *
 * Licensed under the Educational Community 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.opensource.org/licenses/ECL-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.sakaiproject.sitestats.tool.wicket.components;

import org.apache.wicket.AttributeModifier;
import org.apache.wicket.Component;
import org.apache.wicket.request.cycle.RequestCycle;
import org.apache.wicket.ajax.AbstractDefaultAjaxBehavior;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.ajax.attributes.AjaxRequestAttributes;
import org.apache.wicket.ajax.AjaxChannel;
import org.apache.wicket.markup.head.IHeaderResponse;
import org.apache.wicket.markup.head.OnDomReadyHeaderItem;
import org.apache.wicket.markup.html.basic.Label;
import org.apache.wicket.markup.html.panel.Fragment;
import org.apache.wicket.markup.html.panel.Panel;
import org.apache.wicket.model.Model;

/**
 * @author Nuno Fernandes
 */
public abstract class AjaxLazyLoadFragment extends Panel {
    private static final long serialVersionUID = 1L;

    // State:
    // 0:add loading component
    // 1:loading component added, waiting for ajax replace
    // 2:ajax replacement completed
    private byte state = 0;

    /**
     * @param id
     */
    public AjaxLazyLoadFragment(final String id) {
        super(id);
        setOutputMarkupId(true);

        final AbstractDefaultAjaxBehavior behavior = new AbstractDefaultAjaxBehavior() {
            @Override
            protected void respond(AjaxRequestTarget target) {
                Fragment fragment = getLazyLoadFragment("content");
                AjaxLazyLoadFragment.this.replace(fragment.setRenderBodyOnly(true));
                target.add(AjaxLazyLoadFragment.this);
                setState((byte) 2);
            }

            @Override
            public void renderHead(Component component, IHeaderResponse response) {
                response.render(OnDomReadyHeaderItem.forScript(getCallbackScript().toString()));
                super.renderHead(component, response);
            }

            @Override
            protected void updateAjaxAttributes(AjaxRequestAttributes attributes) {
                super.updateAjaxAttributes(attributes);

                attributes.setChannel(new AjaxChannel(getId()));
            }

            @Override
            public boolean isEnabled(Component component) {
                return state < 2;
            }
        };
        add(behavior);

    }

    @Override
    protected void onBeforeRender() {
        if (state == 0) {
            final Component loadingComponent = getLoadingComponent("content");
            add(loadingComponent.setRenderBodyOnly(true));
            setState((byte) 1);
        }
        super.onBeforeRender();
    }

    /**
     * @param markupId The frgment markupid.
     * @return The fragment that must be lazy created.
     */
    public abstract Fragment getLazyLoadFragment(String markupId);

    /**
     * @param markupId The components markupid.
     * @return The component to show while the real component is being created.
     */
    public Component getLoadingComponent(String markupId) {
        Label indicator = new Label(markupId,
                "<img src=\"" + RequestCycle.get().urlFor(AbstractDefaultAjaxBehavior.INDICATOR, null) + "\"/>");
        indicator.setEscapeModelStrings(false);
        indicator.add(new AttributeModifier("title", new Model("...")));
        return indicator;
    }

    private void setState(byte state) {
        if (this.state != state) {
            addStateChange();
        }
        this.state = state;
    }

}