Java tutorial
/* * Copyright 2008 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.nanosim.client; import com.google.gwt.core.client.GWT; import com.google.gwt.event.logical.shared.SelectionEvent; import com.google.gwt.event.logical.shared.SelectionHandler; import com.google.gwt.http.client.Request; import com.google.gwt.http.client.RequestBuilder; import com.google.gwt.http.client.RequestCallback; import com.google.gwt.http.client.RequestException; import com.google.gwt.http.client.Response; import com.google.gwt.i18n.client.Constants; import com.google.gwt.user.client.DOM; import com.google.gwt.user.client.ui.DeckPanel; import com.google.gwt.user.client.ui.HTML; import com.google.gwt.user.client.ui.LazyPanel; import com.google.gwt.user.client.ui.TabBar; import com.google.gwt.user.client.ui.VerticalPanel; import com.google.gwt.user.client.ui.Widget; import java.util.HashMap; import java.util.Map; /** * <p> * A widget used to show GWT examples in the ContentPanel. It includes a tab bar * with options to view the example, view the source, or view the css style * rules. * </p> * <p> * This {@link Widget} extends {@link LazyPanel} so that the content is not * rendered until the widget first becomes visible. The data in the source and * css tabs are loaded using an RPC call to the server. * </p> * <h3>CSS Style Rules</h3> * <ul class="css"> * <li>.sc-ContentWidget { Applied to the entire widget }</li> * <li>.sc-ContentWidget-tabBar { Applied to the TabBar }</li> * <li>.sc-ContentWidget-deckPanel { Applied to the DeckPanel }</li> * <li>.sc-ContentWidget-name { Applied to the name }</li> * <li>.sc-ContentWidget-description { Applied to the description }</li> * </ul> */ public abstract class ContentWidget extends LazyPanel implements SelectionHandler<Integer> { /** * The constants used in this Content Widget. */ public static interface CwConstants extends Constants { String contentWidgetExample(); String contentWidgetSource(); String contentWidgetStyle(); } /** * The default style name. */ private static final String DEFAULT_STYLE_NAME = "sc-ContentWidget"; /** * The static loading image displayed when loading CSS or source code. */ private static String loadingImage; /** * An instance of the constants. */ private final CwConstants constants; /** * The deck panel with the contents. */ private DeckPanel deckPanel = null; /** * A boolean indicating whether or not the RPC request for the source code has * been sent. */ private boolean sourceLoaded = false; /** * The widget used to display source code. */ private HTML sourceWidget = null; /** * A mapping of themes to style definitions. */ private Map<String, String> styleDefs = null; /** * The widget used to display css style. */ private HTML styleWidget = null; /** * The tab bar of options. */ private TabBar tabBar = null; /** * Constructor. * * @param constants the constants */ public ContentWidget(CwConstants constants) { this.constants = constants; tabBar = new TabBar(); } /** * Add an item to this content widget. Should not be called before * {@link #onInitializeComplete} has been called. * * @param w the widget to add * @param tabText the text to display in the tab */ public void add(Widget w, String tabText) { tabBar.addTab(tabText); deckPanel.add(w); } /** * Get the description of this example. * * @return a description for this example */ public abstract String getDescription(); /** * Get the name of this example to use as a title. * * @return a name for this example */ public abstract String getName(); /** * @return the tab bar */ public TabBar getTabBar() { return tabBar; } /** * Returns true if this widget has a source section. * * @return true if source tab available */ public boolean hasSource() { return true; } /** * Returns true if this widget has a style section. * * @return true if style tab available */ public boolean hasStyle() { return true; } /** * When the widget is first initialized, this method is called. If it returns * a Widget, the widget will be added as the first tab. Return null to disable * the first tab. * * @return the widget to add to the first tab */ public abstract Widget onInitialize(); /** * Called when initialization has completed and the widget has been added to * the page. */ public void onInitializeComplete() { } public void onSelection(SelectionEvent<Integer> event) { // Show the associated widget in the deck panel int tabIndex = event.getSelectedItem().intValue(); deckPanel.showWidget(tabIndex); // Load the source code String tabHTML = getTabBar().getTabHTML(tabIndex); if (!sourceLoaded && tabHTML.equals(constants.contentWidgetSource())) { sourceLoaded = true; String className = this.getClass().getName(); className = className.substring(className.lastIndexOf(".") + 1); requestSourceContents(NanosimConstants.DST_SOURCE_EXAMPLE + className + ".html", sourceWidget, null); } // Load the style definitions if (hasStyle() && tabHTML.equals(constants.contentWidgetStyle())) { final String theme = HomeScreen.CUR_THEME; if (styleDefs.containsKey(theme)) { styleWidget.setHTML(styleDefs.get(theme)); } else { styleDefs.put(theme, ""); RequestCallback callback = new RequestCallback() { public void onError(Request request, Throwable exception) { styleDefs.put(theme, "Style not available."); } public void onResponseReceived(Request request, Response response) { styleDefs.put(theme, response.getText()); } }; String srcPath = NanosimConstants.DST_SOURCE_STYLE + theme; String className = this.getClass().getName(); className = className.substring(className.lastIndexOf(".") + 1); requestSourceContents(srcPath + "/" + className + ".html", styleWidget, callback); } } } /** * Select a tab. * * @param index the tab index */ public void selectTab(int index) { tabBar.selectTab(index); } /** * Initialize this widget by creating the elements that should be added to the * page. */ protected final Widget createWidget() { deckPanel = new DeckPanel(); setStyleName(DEFAULT_STYLE_NAME); // Add a tab handler tabBar.addSelectionHandler(this); // Create a container for the main example final VerticalPanel vPanel = new VerticalPanel(); add(vPanel, constants.contentWidgetExample()); // Add the name HTML nameWidget = new HTML(getName()); nameWidget.setStyleName(DEFAULT_STYLE_NAME + "-name"); vPanel.add(nameWidget); // Add the description HTML descWidget = new HTML(getDescription()); descWidget.setStyleName(DEFAULT_STYLE_NAME + "-description"); vPanel.add(descWidget); // Add source code tab if (hasSource()) { sourceWidget = new HTML(); add(sourceWidget, constants.contentWidgetSource()); } else { sourceLoaded = true; } // Add style tab if (hasStyle()) { styleDefs = new HashMap<String, String>(); styleWidget = new HTML(); add(styleWidget, constants.contentWidgetStyle()); } // Initialize the Nanosim widget (if any) and add it to the page Widget widget = onInitialize(); if (widget != null) { vPanel.add(widget); } onInitializeComplete(); return deckPanel; } @Override protected void onLoad() { ensureWidget(); // Select the first tab if (getTabBar().getTabCount() > 0) { tabBar.selectTab(0); } } /** * Load the contents of a remote file into the specified widget. * * @param url a partial path relative to the module base URL * @param target the target Widget to place the contents * @param callback the callback when the call completes */ protected void requestSourceContents(String url, final HTML target, final RequestCallback callback) { // Show the loading image if (loadingImage == null) { loadingImage = "<img src=\"" + GWT.getModuleBaseURL() + "images/loading.gif\">"; } DOM.setStyleAttribute(target.getElement(), "textAlign", "left"); target.setHTML(" " + loadingImage); // Request the contents of the file RequestBuilder builder = new RequestBuilder(RequestBuilder.GET, GWT.getModuleBaseURL() + url); RequestCallback realCallback = new RequestCallback() { public void onError(Request request, Throwable exception) { target.setHTML("Cannot find resource"); if (callback != null) { callback.onError(request, exception); } } public void onResponseReceived(Request request, Response response) { target.setHTML(response.getText()); if (callback != null) { callback.onResponseReceived(request, response); } } }; builder.setCallback(realCallback); // Send the request Request request = null; try { request = builder.send(); } catch (RequestException e) { realCallback.onError(request, e); } } }