net.dontdrinkandroot.wicket.behavior.ajax.ScrollToBottomBehavior.java Source code

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Here is the source code for net.dontdrinkandroot.wicket.behavior.ajax.ScrollToBottomBehavior.java

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/**
 * Copyright (C) 2012-2014 Philip W. Sorst <philip@sorst.net>
 * and individual contributors as indicated
 * by the @authors tag.
 *
 * 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 net.dontdrinkandroot.wicket.behavior.ajax;

import org.apache.wicket.Component;
import org.apache.wicket.Page;
import org.apache.wicket.WicketRuntimeException;
import org.apache.wicket.ajax.AbstractDefaultAjaxBehavior;
import org.apache.wicket.ajax.attributes.AjaxCallListener;
import org.apache.wicket.ajax.attributes.AjaxRequestAttributes;
import org.apache.wicket.markup.head.IHeaderResponse;
import org.apache.wicket.markup.head.JavaScriptHeaderItem;

//TODO: This works only for pages at the moment
public abstract class ScrollToBottomBehavior extends AbstractDefaultAjaxBehavior {

    private final int offset;

    private static final String ACTIVE_PREFIX = "scollToBottomActive";

    public ScrollToBottomBehavior(int offset) {

        this.offset = offset;
    }

    @Override
    public void renderHead(Component component, IHeaderResponse response) {

        super.renderHead(component, response);

        String componentSelector;
        if (component instanceof Page) {
            componentSelector = "window";
        } else {
            componentSelector = String.format("'#%s'", component.getMarkupId());
        }

        StringBuffer scriptBuffer = new StringBuffer();
        scriptBuffer.append(String.format("var %s = true;", this.getActiveVarName(component)));
        scriptBuffer.append(String.format("$(%s).scroll(function () {", componentSelector));
        scriptBuffer.append(
                String.format("if (%s && $(%s).scrollTop() >= $(document).height() - $(%s).height() - %d) {",
                        this.getActiveVarName(component), componentSelector, componentSelector, this.offset));
        scriptBuffer.append(String.format("%s = false;", this.getActiveVarName(component)));
        scriptBuffer.append(this.getCallbackScript());
        scriptBuffer.append("}");
        scriptBuffer.append("});");

        response.render(JavaScriptHeaderItem.forScript(scriptBuffer, "scrollToBottom"));
    }

    @Override
    protected void updateAjaxAttributes(AjaxRequestAttributes attributes) {

        super.updateAjaxAttributes(attributes);
        attributes.getAjaxCallListeners().add(new AjaxCallListener() {

            @Override
            public CharSequence getSuccessHandler(Component component) {

                return String.format("%s = true;",
                        ScrollToBottomBehavior.this.getActiveVarName(ScrollToBottomBehavior.this.getComponent()));
            }
        });
    }

    private String getActiveVarName(Component component) {

        return ScrollToBottomBehavior.ACTIVE_PREFIX + "_" + component.getPath();
    }

    @Override
    public void onConfigure(Component component) {

        super.onConfigure(component);

        if (!(component instanceof Page)) {
            throw new WicketRuntimeException("Behavior can only be bound to a Page");
        }
    }
}