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.FeatureEntry; import com.google.gwt.gdata.client.maps.FeatureEntryCallback; import com.google.gwt.gdata.client.maps.FeatureFeed; import com.google.gwt.gdata.client.maps.FeatureFeedCallback; import com.google.gwt.gdata.client.maps.MapEntry; 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 update a map feature. */ public class MapsDeleteMapFeatureDemo 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 MapsDeleteMapFeatureDemo(); } @Override public String getDescription() { return "<p>This sample demonstrates how to delete an existing " + "map feature of the authenticated user. It retrieves a list of " + "the user's maps and deletes the first map feature with a title " + "that starts with 'GWT-Maps-Client'.</p>"; } @Override public String getName() { return "Maps - Deleting a map feature"; } }; } 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 MapsDeleteMapFeatureDemo() { 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 fature entry using the Maps service and * the feature entry uri. * On success and failure, display a status message. * * @param featureEntryUri The uri of the feature entry to delete */ private void deleteFeature(String featureEntryUri) { showStatus("Deleting map feature...", false); service.deleteEntry(featureEntryUri, new FeatureEntryCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while deleting a map feature: " + caught.getMessage(), true); } public void onSuccess(FeatureEntry result) { showStatus("Deleted a map feature.", false); } }); } /** * Retrieve the features feed for a given map using the * Maps service and the features 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 feature entry with a title * starting with "GWT-Maps-Client" and calls deleteFeature to * delete the feature. * If no feature is found, a message is displayed. * * @param mapEntryUri The uri of the map entry for which to * retrieve the features feed */ private void getFeatures(String mapEntryUri) { String featuresFeedUri = mapEntryUri.replace("/feeds/maps/", "/feeds/features/") + "/full"; showStatus("Loading features feed...", false); service.getFeatureFeed(featuresFeedUri, new FeatureFeedCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while retrieving the features feed: " + caught.getMessage(), true); } public void onSuccess(FeatureFeed result) { FeatureEntry[] entries = result.getEntries(); FeatureEntry targetFeature = null; for (FeatureEntry entry : entries) { if (entry.getTitle().getText().startsWith("GWT-Maps-Client")) { targetFeature = entry; break; } } if (targetFeature == null) { showStatus("No map feature found that contains 'GWT-Maps-Client' " + "in the title.", false); } else { String featureEntryUri = targetFeature.getSelfLink().getHref(); deleteFeature(featureEntryUri); } } }); } /** * Retrieve the maps feed using the Maps service and * the maps feed uri. * 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 getFeatures to * retrieve the map's features. * 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.getId().getValue(); getFeatures(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_DeleteMapFeatureDemo_v2.0"); if (User.getStatus(scope) == AuthSubStatus.LOGGED_IN) { Button startButton = new Button("Delete a map feature"); 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); } } }