com.arcbees.gquery.tooltip.client.contactcell.ShowMorePagerPanel.java Source code

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Here is the source code for com.arcbees.gquery.tooltip.client.contactcell.ShowMorePagerPanel.java

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/**
 * Copyright 2014 ArcBees Inc.
 *
 * 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 com.arcbees.gquery.tooltip.client.contactcell;

import com.arcbees.gquery.tooltip.client.Tooltip;
import com.google.gwt.event.dom.client.ScrollEvent;
import com.google.gwt.event.dom.client.ScrollHandler;
import com.google.gwt.query.client.GQuery;
import com.google.gwt.user.cellview.client.AbstractPager;
import com.google.gwt.user.client.ui.FlowPanel;
import com.google.gwt.user.client.ui.SimplePanel;
import com.google.gwt.user.client.ui.Widget;
import com.google.gwt.view.client.HasRows;

/**
 * A scrolling pager that automatically increases the range every time the
 * scroll bar reaches the bottom.
 * <p/>
 * Code coming from GWT showcase. We just add code to destroy all tooltips when range change in order to release
 * resources and avoid ghodt tooltip
 */
public class ShowMorePagerPanel extends AbstractPager {
    /**
     * The default increment size.
     */
    private static final int DEFAULT_INCREMENT = 20;
    /**
     * The increment size.
     */
    private int incrementSize = DEFAULT_INCREMENT;
    /**
     * The last scroll position.
     */
    private int lastScrollPos = 0;
    /**
     * The scrollable panel.
     */
    private final SimplePanel scrollable = new SimplePanel();

    /**
     * Construct a new {@link ShowMorePagerPanel}.
     */
    public ShowMorePagerPanel() {
        init();

        // Handle scroll events.
        scrollable.addDomHandler(new ScrollHandler() {
            public void onScroll(ScrollEvent event) {
                // If scrolling up, ignore the event.
                int oldScrollPos = lastScrollPos;
                lastScrollPos = scrollable.getElement().getScrollTop();
                if (oldScrollPos >= lastScrollPos) {
                    return;
                }

                HasRows display = getDisplay();
                if (display == null) {
                    return;
                }
                int maxScrollTop = scrollable.getWidget().getOffsetHeight() - scrollable.getOffsetHeight();
                if (lastScrollPos >= maxScrollTop) {
                    // We are near the end, so increase the page size.
                    int newPageSize = Math.min(display.getVisibleRange().getLength() + incrementSize,
                            display.getRowCount());
                    //all children will be replaced, ensure to destroy existing tooltip in order to avoid ghost
                    // tooltips
                    GQuery.$(".tooltipable", (Widget) display).as(Tooltip.Tooltip).destroy();
                    display.setVisibleRange(0, newPageSize);
                }
            }
        }, ScrollEvent.getType());
    }

    /**
     * Get the number of rows by which the range is increased when the scrollbar
     * reaches the bottom.
     *
     * @return the increment size
     */
    public int getIncrementSize() {
        return incrementSize;
    }

    @Override
    public void setDisplay(HasRows display) {
        assert display instanceof Widget : "display must extend Widget";
        scrollable.setWidget((Widget) display);
        super.setDisplay(display);
    }

    /**
     * Set the number of rows by which the range is increased when the scrollbar
     * reaches the bottom.
     *
     * @param incrementSize the incremental number of rows
     */
    public void setIncrementSize(int incrementSize) {
        this.incrementSize = incrementSize;
    }

    @Override
    protected void onRangeOrRowCountChanged() {
    }

    private void init() {
        FlowPanel p = new FlowPanel();
        p.add(scrollable);
        scrollable.addStyleName("pager");
        initWidget(p);
    }
}