/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.wicket.extensions.ajax.markup.html;
import org.apache.wicket.Component;
import org.apache.wicket.ajax.AbstractDefaultAjaxBehavior;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.ajax.attributes.AjaxRequestAttributes;
import org.apache.wicket.markup.head.IHeaderResponse;
import org.apache.wicket.markup.head.JavaScriptHeaderItem;
import org.apache.wicket.markup.html.basic.Label;
import org.apache.wicket.markup.html.panel.Panel;
import org.apache.wicket.model.IModel;
import org.apache.wicket.request.IRequestHandler;
import org.apache.wicket.request.cycle.RequestCycle;
import org.apache.wicket.request.handler.resource.ResourceReferenceRequestHandler;
/**
* A panel where you can lazy load another panel. This can be used if you have a panel/component
* that is pretty heavy in creation and you first want to show the user the page and then replace
* the panel when it is ready.
*
* @author jcompagner
*
* @since 1.3
*/
public abstract class AjaxLazyLoadPanel extends Panel
{
private static final long serialVersionUID = 1L;
/**
* The component id which will be used to load the lazily loaded component.
*/
public static final String LAZY_LOAD_COMPONENT_ID = "content";
// state,
// 0:add loading component
// 1:loading component added, waiting for ajax replace
// 2:ajax replacement completed
private byte state = 0;
/**
* Constructor
*
* @param id
*/
public AjaxLazyLoadPanel(final String id)
{
this(id, null);
}
/**
* Constructor
*
* @param id
* @param model
*/
public AjaxLazyLoadPanel(final String id, final IModel<?> model)
{
super(id, model);
setOutputMarkupId(true);
add(new AbstractDefaultAjaxBehavior()
{
private static final long serialVersionUID = 1L;
@Override
protected void respond(final AjaxRequestTarget target)
{
if (state < 2)
{
Component component = getLazyLoadComponent(LAZY_LOAD_COMPONENT_ID);
AjaxLazyLoadPanel.this.replace(component);
setState((byte)2);
}
target.add(AjaxLazyLoadPanel.this);
}
@Override
protected void updateAjaxAttributes(AjaxRequestAttributes attributes)
{
super.updateAjaxAttributes(attributes);
AjaxLazyLoadPanel.this.updateAjaxAttributes(attributes);
}
@Override
public void renderHead(final Component component, final IHeaderResponse response)
{
super.renderHead(component, response);
if (state < 2)
{
CharSequence js = getCallbackScript(component);
handleCallbackScript(response, js, component);
}
}
});
}
protected void updateAjaxAttributes(AjaxRequestAttributes attributes)
{
attributes.setEventNames("domready");
}
/**
* Allows subclasses to change the callback script if needed.
*
* @param response
* @param callbackScript
* @param component
*/
protected void handleCallbackScript(final IHeaderResponse response,
final CharSequence callbackScript, final Component component)
{
response.render(JavaScriptHeaderItem.forScript(callbackScript, "lazy-load-" + component.getMarkupId()));
}
/**
* @see org.apache.wicket.Component#onBeforeRender()
*/
@Override
protected void onBeforeRender()
{
if (state == 0)
{
add(getLoadingComponent(LAZY_LOAD_COMPONENT_ID));
setState((byte)1);
}
super.onBeforeRender();
}
/**
*
* @param state
*/
private void setState(final byte state)
{
this.state = state;
getPage().dirty();
}
/**
*
* @param markupId
* The components markupid.
* @return The component that must be lazy created. You may call setRenderBodyOnly(true) on this
* component if you need the body only.
*/
public abstract Component getLazyLoadComponent(String markupId);
/**
* @param markupId
* The components markupid.
* @return The component to show while the real component is being created.
*/
public Component getLoadingComponent(final String markupId)
{
IRequestHandler handler = new ResourceReferenceRequestHandler(
AbstractDefaultAjaxBehavior.INDICATOR);
return new Label(markupId, "<img alt=\"Loading...\" src=\"" +
RequestCycle.get().urlFor(handler) + "\"/>").setEscapeModelStrings(false);
}
}