Java tutorial
/* * 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.cell.client; import com.google.gwt.core.client.GWT; import com.google.gwt.dom.client.Element; import com.google.gwt.dom.client.NativeEvent; import com.google.gwt.i18n.client.LocaleInfo; import com.google.gwt.resources.client.ImageResource; import com.google.gwt.safecss.shared.SafeStyles; import com.google.gwt.safecss.shared.SafeStylesBuilder; import com.google.gwt.safecss.shared.SafeStylesUtils; import com.google.gwt.safehtml.client.SafeHtmlTemplates; import com.google.gwt.safehtml.shared.SafeHtml; import com.google.gwt.safehtml.shared.SafeHtmlBuilder; import com.google.gwt.safehtml.shared.SafeHtmlUtils; import com.google.gwt.user.client.ui.AbstractImagePrototype; import com.google.gwt.user.client.ui.HasVerticalAlignment; import com.google.gwt.user.client.ui.HasVerticalAlignment.VerticalAlignmentConstant; import java.util.Set; /** * A {@link Cell} decorator that adds an icon to another {@link Cell}. * * @param <C> the type that this Cell represents */ public class IconCellDecorator<C> implements Cell<C> { interface Template extends SafeHtmlTemplates { @Template("<div style=\"{0}position:relative;zoom:1;\">{1}<div>{2}</div></div>") SafeHtml outerDiv(SafeStyles padding, SafeHtml icon, SafeHtml cellContents); /** * The wrapper around the image vertically aligned to the bottom. */ @Template("<div style=\"{0}position:absolute;bottom:0px;line-height:0px;\">{1}</div>") SafeHtml imageWrapperBottom(SafeStyles styles, SafeHtml image); /** * The wrapper around the image vertically aligned to the middle. */ @Template("<div style=\"{0}position:absolute;top:50%;line-height:0px;\">{1}</div>") SafeHtml imageWrapperMiddle(SafeStyles styles, SafeHtml image); /** * The wrapper around the image vertically aligned to the top. */ @Template("<div style=\"{0}position:absolute;top:0px;line-height:0px;\">{1}</div>") SafeHtml imageWrapperTop(SafeStyles styles, SafeHtml image); } /** * The default spacing between the icon and the text in pixels. */ private static final int DEFAULT_SPACING = 6; private static Template template; private final Cell<C> cell; private final String direction = LocaleInfo.getCurrentLocale().isRTL() ? "right" : "left"; private final SafeHtml iconHtml; private final int imageWidth; private final SafeStyles outerDivPadding; private final SafeHtml placeHolderHtml; /** * Construct a new {@link IconCellDecorator}. The icon and the content will be * middle aligned by default. * * @param icon the icon to use * @param cell the cell to decorate */ public IconCellDecorator(ImageResource icon, Cell<C> cell) { this(icon, cell, HasVerticalAlignment.ALIGN_MIDDLE, DEFAULT_SPACING); } /** * Construct a new {@link IconCellDecorator}. * * @param icon the icon to use * @param cell the cell to decorate * @param valign the vertical alignment attribute of the contents * @param spacing the pixel space between the icon and the cell */ public IconCellDecorator(ImageResource icon, Cell<C> cell, VerticalAlignmentConstant valign, int spacing) { if (template == null) { template = GWT.create(Template.class); } this.cell = cell; this.iconHtml = getImageHtml(icon, valign, false); this.imageWidth = icon.getWidth() + spacing; this.placeHolderHtml = getImageHtml(icon, valign, true); this.outerDivPadding = SafeStylesUtils .fromTrustedString("padding-" + direction + ": " + imageWidth + "px;"); } public boolean dependsOnSelection() { return cell.dependsOnSelection(); } public Set<String> getConsumedEvents() { return cell.getConsumedEvents(); } public boolean handlesSelection() { return cell.handlesSelection(); } public boolean isEditing(Context context, Element parent, C value) { return cell.isEditing(context, getCellParent(parent), value); } public void onBrowserEvent(Context context, Element parent, C value, NativeEvent event, ValueUpdater<C> valueUpdater) { cell.onBrowserEvent(context, getCellParent(parent), value, event, valueUpdater); } public void render(Context context, C value, SafeHtmlBuilder sb) { SafeHtmlBuilder cellBuilder = new SafeHtmlBuilder(); cell.render(context, value, cellBuilder); sb.append(template.outerDiv(outerDivPadding, isIconUsed(value) ? getIconHtml(value) : placeHolderHtml, cellBuilder.toSafeHtml())); } public boolean resetFocus(Context context, Element parent, C value) { return cell.resetFocus(context, getCellParent(parent), value); } public void setValue(Context context, Element parent, C value) { cell.setValue(context, getCellParent(parent), value); } /** * Get the safe HTML string that represents the icon. Override this method to * change the icon based on the value. * * @param value the value being rendered * @return the HTML string that represents the icon */ protected SafeHtml getIconHtml(C value) { return iconHtml; } /** * Check if the icon should be used for the value. If the icon should not be * used, a placeholder of the same size will be used instead. The default * implementations returns true. * * @param value the value being rendered * @return true to use the icon, false to use a placeholder */ protected boolean isIconUsed(C value) { return true; } /** * Get the HTML representation of an image. Visible for testing. * * @param res the {@link ImageResource} to render as HTML * @param valign the vertical alignment * @param isPlaceholder if true, do not include the background image * @return the rendered HTML */ SafeHtml getImageHtml(ImageResource res, VerticalAlignmentConstant valign, boolean isPlaceholder) { // Get the HTML for the image. SafeHtml image; if (isPlaceholder) { image = SafeHtmlUtils.fromTrustedString("<div></div>"); } else { AbstractImagePrototype proto = AbstractImagePrototype.create(res); image = SafeHtmlUtils.fromTrustedString(proto.getHTML()); } // Create the wrapper based on the vertical alignment. SafeStylesBuilder cssStyles = new SafeStylesBuilder().appendTrustedString(direction + ":0px;"); if (HasVerticalAlignment.ALIGN_TOP == valign) { return template.imageWrapperTop(cssStyles.toSafeStyles(), image); } else if (HasVerticalAlignment.ALIGN_BOTTOM == valign) { return template.imageWrapperBottom(cssStyles.toSafeStyles(), image); } else { int halfHeight = (int) Math.round(res.getHeight() / 2.0); cssStyles.appendTrustedString("margin-top:-" + halfHeight + "px;"); return template.imageWrapperMiddle(cssStyles.toSafeStyles(), image); } } /** * Get the parent element of the decorated cell. * * @param parent the parent of this cell * @return the decorated cell's parent */ private Element getCellParent(Element parent) { return parent.getFirstChildElement().getChild(1).cast(); } }