/*
* Copyright 2010 Google 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 it.freedomotic.gwtclient.client.widgets;
import com.google.gwt.event.dom.client.ScrollEvent;
import com.google.gwt.event.dom.client.ScrollHandler;
import com.google.gwt.user.cellview.client.AbstractPager;
import com.google.gwt.user.client.ui.ScrollPanel;
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.
*/
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 ScrollPanel scrollable = new ScrollPanel();
/**
* Construct a new {@link ShowMorePagerPanel}.
*/
public ShowMorePagerPanel() {
initWidget(scrollable);
// Do not let the scrollable take tab focus.
scrollable.getElement().setTabIndex(-1);
// Handle scroll events.
scrollable.addScrollHandler(new ScrollHandler() {
public void onScroll(ScrollEvent event) {
// If scrolling up, ignore the event.
int oldScrollPos = lastScrollPos;
lastScrollPos = scrollable.getVerticalScrollPosition();
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());
display.setVisibleRange(0, newPageSize);
}
}
});
}
/**
* 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() {
}
}