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.gdata.sample.hellogdata.client; import com.google.gwt.accounts.client.AuthSubStatus; import com.google.gwt.accounts.client.User; import com.google.gwt.event.dom.client.ClickEvent; import com.google.gwt.event.dom.client.ClickHandler; import com.google.gwt.gdata.client.GData; import com.google.gwt.gdata.client.GDataSystemPackage; import com.google.gwt.gdata.client.impl.CallErrorException; import com.google.gwt.gdata.client.maps.MapEntry; import com.google.gwt.gdata.client.maps.MapEntryCallback; import com.google.gwt.gdata.client.maps.MapFeed; import com.google.gwt.gdata.client.maps.MapFeedCallback; import com.google.gwt.gdata.client.maps.MapsService; import com.google.gwt.user.client.ui.Button; import com.google.gwt.user.client.ui.FlexTable; import com.google.gwt.user.client.ui.Label; /** * The following example demonstrates how to delete a map. */ public class MapsDeleteMapDemo extends GDataDemo { /** * This method is used by the main sample app to obtain * information on this sample and a sample instance. * * @return An instance of this demo. */ public static GDataDemoInfo init() { return new GDataDemoInfo() { @Override public GDataDemo createInstance() { return new MapsDeleteMapDemo(); } @Override public String getDescription() { return "<p>This sample code demonstrates how to delete an existing " + "map of the authenticated user. It retrieves a list of the " + "user's maps, and deletes the first map with a title that " + "starts with 'GWT-Maps-Client'.</p>"; } @Override public String getName() { return "Maps - Deleting a map"; } }; } private MapsService service; private FlexTable mainPanel; private final String scope = "http://maps.google.com/maps/feeds/maps/"; /** * Setup the Google Maps service and create the main content panel. * If the user is not logged on to Google Maps display a message, * otherwise start the demo by retrieving the user's maps. */ public MapsDeleteMapDemo() { mainPanel = new FlexTable(); initWidget(mainPanel); if (!GData.isLoaded(GDataSystemPackage.MAPS)) { showStatus("Loading the GData Maps package...", false); GData.loadGDataApi(GDATA_API_KEY, new Runnable() { public void run() { startDemo(); } }, GDataSystemPackage.MAPS); } else { startDemo(); } } /** * Delete a map entry using the Maps service and * the map entry uri. * On success and failure, display a status message. * * @param mapEntryUri The uri of the map entry to delete */ private void deleteMap(String mapEntryUri) { showStatus("Deleting map...", false); service.deleteEntry(mapEntryUri, new MapEntryCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while retrieving the maps feed: " + caught.getMessage(), true); } public void onSuccess(MapEntry result) { showStatus("Deleted a map.", false); } }); } /** * Retrieve the maps feed using the Maps service and * the maps feed uri. In GData all get, insert, update * and delete methods always receive a callback defining * success and failure handlers. * Here, the failure handler displays an error message while the * success handler obtains the first map entry with a title * starting with "GWT-Maps-Client" and calls deleteMap to * delete the map. * If no map is found, a message is displayed. * * @param mapsFeedUri The uri of the map feed */ private void getMaps(String mapsFeedUri) { showStatus("Loading maps feed...", false); service.getMapFeed(mapsFeedUri, new MapFeedCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while retrieving the maps feed: " + caught.getMessage(), true); } public void onSuccess(MapFeed result) { MapEntry[] entries = result.getEntries(); MapEntry targetMap = null; for (MapEntry entry : entries) { if (entry.getTitle().getText().startsWith("GWT-Maps-Client")) { targetMap = entry; break; } } if (targetMap == null) { showStatus("No map found that contains 'GWT-Maps-Client' in the title.", false); } else { String mapEntryUri = targetMap.getSelfLink().getHref(); deleteMap(mapEntryUri); } } }); } /** * Displays a status message to the user. * * @param message The message to display. * @param isError Indicates whether the status is an error status. */ private void showStatus(String message, boolean isError) { mainPanel.clear(); mainPanel.insertRow(0); mainPanel.addCell(0); Label msg = new Label(message); if (isError) { msg.setStylePrimaryName("hm-error"); } mainPanel.setWidget(0, 0, msg); } /** * Starts this demo. */ private void startDemo() { service = MapsService.newInstance("HelloGData_Maps_DeleteMapDemo_v2.0"); if (User.getStatus(scope) == AuthSubStatus.LOGGED_IN) { Button startButton = new Button("Delete a map"); startButton.addClickHandler(new ClickHandler() { public void onClick(ClickEvent event) { getMaps("http://maps.google.com/maps/feeds/maps/default/full"); } }); mainPanel.setWidget(0, 0, startButton); } else { showStatus("You are not logged on to Google Maps.", true); } } }