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.google.gwt.sample.showcase.client; import com.google.gwt.core.client.GWT; import com.google.gwt.event.logical.shared.HasValueChangeHandlers; import com.google.gwt.event.logical.shared.ValueChangeEvent; import com.google.gwt.event.logical.shared.ValueChangeHandler; import com.google.gwt.event.shared.HandlerRegistration; 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.LocaleInfo; import com.google.gwt.safehtml.shared.SafeHtml; import com.google.gwt.safehtml.shared.SafeHtmlUtils; import com.google.gwt.user.client.Window; import com.google.gwt.user.client.rpc.AsyncCallback; import com.google.gwt.user.client.ui.SimpleLayoutPanel; import com.google.gwt.user.client.ui.Widget; import java.util.ArrayList; import java.util.Collections; import java.util.HashMap; import java.util.List; import java.util.Map; /** * <p> * A widget used to show GWT examples in the ContentPanel. * </p> * <p> * This {@link Widget} uses a lazy initialization mechanism so that the content * is not rendered until the onInitialize method is called, which happens the * first time the {@link Widget} is added to the page. The data in the source * and css tabs are loaded using an RPC call to the server. * </p> */ public abstract class ContentWidget extends SimpleLayoutPanel implements HasValueChangeHandlers<String> { /** * Generic callback used for asynchronously loaded data. * * @param <T> the data type */ public static interface Callback<T> { void onError(); void onSuccess(T value); } /** * Get the simple filename of a class. * * @param c the class */ protected static String getSimpleName(Class<?> c) { String name = c.getName(); return name.substring(name.lastIndexOf(".") + 1); } /** * A description of the example. */ private final SafeHtml description; /** * True if this example has associated styles, false if not. */ private final boolean hasStyle; /** * The name of the example. */ private final String name; /** * A mapping of filenames to their raw source code. The map is populated as * source is loaded. */ private final Map<String, String> rawSource = new HashMap<String, String>(); /** * A list of filenames of the raw source code included with this example. */ private final List<String> rawSourceFilenames = new ArrayList<String>(); /** * The source code associated with this widget. */ private String sourceCode; /** * A style definitions used by this widget. */ private String styleDefs; /** * The view that holds the name, description, and example. */ private ContentWidgetView view; /** * Whether the demo widget has been initialized. */ private boolean widgetInitialized; /** * Whether the demo widget is (asynchronously) initializing. */ private boolean widgetInitializing; /** * Construct a {@link ContentWidget}. * * @param name the text name of the example * @param description a text description of the example * @param hasStyle true if the example has associated styles * @param rawSourceFiles the list of raw source files to include */ public ContentWidget(String name, String description, boolean hasStyle, String... rawSourceFiles) { this(name, SafeHtmlUtils.fromString(description), hasStyle, rawSourceFiles); } /** * Construct a {@link ContentWidget}. * * @param name the text name of the example * @param description a safe html description of the example * @param hasStyle true if the example has associated styles * @param rawSourceFiles the list of raw source files to include */ public ContentWidget(String name, SafeHtml description, boolean hasStyle, String... rawSourceFiles) { this.name = name; this.description = description; this.hasStyle = hasStyle; if (rawSourceFiles != null) { for (String rawSourceFile : rawSourceFiles) { rawSourceFilenames.add(rawSourceFile); } } } public HandlerRegistration addValueChangeHandler(ValueChangeHandler<String> handler) { return addHandler(handler, ValueChangeEvent.getType()); } /** * Get the description of this example. * * @return a description for this example */ public final SafeHtml getDescription() { return description; } /** * Get the name of this example to use as a title. * * @return a name for this example */ public final String getName() { return name; } /** * Get the source code for a raw file. * * @param filename the filename to load * @param callback the callback to call when loaded */ public void getRawSource(final String filename, final Callback<String> callback) { if (rawSource.containsKey(filename)) { callback.onSuccess(rawSource.get(filename)); } else { RequestCallback rc = new RequestCallback() { public void onError(Request request, Throwable exception) { callback.onError(); } public void onResponseReceived(Request request, Response response) { String text = response.getText(); rawSource.put(filename, text); callback.onSuccess(text); } }; String className = this.getClass().getName(); className = className.substring(className.lastIndexOf(".") + 1); sendSourceRequest(rc, ShowcaseConstants.DST_SOURCE_RAW + filename + ".html"); } } /** * Get the filenames of the raw source files. * * @return the raw source files. */ public List<String> getRawSourceFilenames() { return Collections.unmodifiableList(rawSourceFilenames); } /** * Request the styles associated with the widget. * * @param callback the callback used when the styles become available */ public void getStyle(final Callback<String> callback) { if (styleDefs != null) { callback.onSuccess(styleDefs); } else { RequestCallback rc = new RequestCallback() { public void onError(Request request, Throwable exception) { callback.onError(); } public void onResponseReceived(Request request, Response response) { styleDefs = response.getText(); callback.onSuccess(styleDefs); } }; String srcPath = ShowcaseConstants.DST_SOURCE_STYLE + Showcase.THEME; if (LocaleInfo.getCurrentLocale().isRTL()) { srcPath += "_rtl"; } String className = this.getClass().getName(); className = className.substring(className.lastIndexOf(".") + 1); sendSourceRequest(rc, srcPath + "/" + className + ".html"); } } /** * Request the source code associated with the widget. * * @param callback the callback used when the source become available */ public void getSource(final Callback<String> callback) { if (sourceCode != null) { callback.onSuccess(sourceCode); } else { RequestCallback rc = new RequestCallback() { public void onError(Request request, Throwable exception) { callback.onError(); } public void onResponseReceived(Request request, Response response) { sourceCode = response.getText(); callback.onSuccess(sourceCode); } }; String className = this.getClass().getName(); className = className.substring(className.lastIndexOf(".") + 1); sendSourceRequest(rc, ShowcaseConstants.DST_SOURCE_EXAMPLE + className + ".html"); } } /** * Check if the widget should have margins. * * @return true to use margins, false to flush against edges */ public boolean hasMargins() { return true; } /** * Check if the widget should be wrapped in a scrollable div. * * @return true to use add scrollbars, false not to */ public boolean hasScrollableContent() { return true; } /** * Returns true if this widget has a style section. * * @return true if style tab available */ public final boolean hasStyle() { return hasStyle; } /** * 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() { } protected abstract void asyncOnInitialize(final AsyncCallback<Widget> callback); /** * Fire a {@link ValueChangeEvent} indicating that the user wishes to see the * specified source file. * * @param filename the filename that the user wishes to see */ protected void fireRawSourceRequest(String filename) { if (!rawSourceFilenames.contains(filename)) { throw new IllegalArgumentException("Filename is not registered with this example: " + filename); } ValueChangeEvent.fire(this, filename); } @Override protected void onLoad() { if (view == null) { view = new ContentWidgetView(hasMargins(), hasScrollableContent()); view.setName(getName()); view.setDescription(getDescription()); setWidget(view); } ensureWidgetInitialized(); super.onLoad(); } /** * Ensure that the demo widget has been initialized. Note that initialization * can fail if there is a network failure. */ private void ensureWidgetInitialized() { if (widgetInitializing || widgetInitialized) { return; } widgetInitializing = true; asyncOnInitialize(new AsyncCallback<Widget>() { public void onFailure(Throwable reason) { widgetInitializing = false; Window.alert("Failed to download code for this widget (" + reason + ")"); } public void onSuccess(Widget result) { widgetInitializing = false; widgetInitialized = true; Widget widget = result; if (widget != null) { view.setExample(widget); } onInitializeComplete(); } }); } /** * Send a request for source code. * * @param callback the {@link RequestCallback} to send * @param url the URL to target */ private void sendSourceRequest(RequestCallback callback, String url) { RequestBuilder builder = new RequestBuilder(RequestBuilder.GET, GWT.getModuleBaseURL() + url); builder.setCallback(callback); try { builder.send(); } catch (RequestException e) { callback.onError(null, e); } } }