| /* |
| * 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 com.google.gwt.sample.showcase.client.content.cell; |
| |
| 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() { |
| } |
| } |