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.GDataRequestParameters; import com.google.gwt.gdata.client.GDataSystemPackage; import com.google.gwt.gdata.client.contacts.ContactGroupEntry; import com.google.gwt.gdata.client.contacts.ContactGroupEntryCallback; import com.google.gwt.gdata.client.contacts.ContactGroupFeed; import com.google.gwt.gdata.client.contacts.ContactGroupFeedCallback; import com.google.gwt.gdata.client.contacts.ContactsService; import com.google.gwt.gdata.client.impl.CallErrorException; 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 contact group. */ public class ContactsDeleteContactGroupDemo 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 ContactsDeleteContactGroupDemo(); } @Override public String getDescription() { return "<p>This sample demonstrates how to delete a contact " + "group entry. It obtains the contact group that has a title " + "that starts with 'GWT-Contacts-Client' and deletes the " + "group.</p>"; } @Override public String getName() { return "Contacts - Deleting contact groups"; } }; } private ContactsService service; private FlexTable mainPanel; private final String scope = "http://www.google.com/m8/feeds/"; /** * Setup the Contacts service and create the main content panel. * If the user is not logged on to Contacts display a message, * otherwise start the demo by retrieving the user's contact groups. */ public ContactsDeleteContactGroupDemo() { mainPanel = new FlexTable(); initWidget(mainPanel); if (!GData.isLoaded(GDataSystemPackage.CONTACTS)) { showStatus("Loading the GData Contacts package...", false); GData.loadGDataApi(GDATA_API_KEY, new Runnable() { public void run() { startDemo(); } }, GDataSystemPackage.CONTACTS); } else { startDemo(); } } /** * Delete a contact group entry using the Contacts service and * the contact group entry uri. * On success and failure, display a status message. * * @param contactGroupEntryUri The uri of the contact group entry to delete * @param etag The etag of the entry to delete */ private void deleteContactGroup(String contactGroupEntryUri, String etag) { showStatus("Deleting a contact group...", false); GDataRequestParameters pars = GDataRequestParameters.newInstance(); pars.setEtag(etag); service.deleteEntry(contactGroupEntryUri, new ContactGroupEntryCallback() { public void onFailure(CallErrorException caught) { showStatus("An error occurred while deleting a contact group: " + caught.getMessage(), true); } public void onSuccess(ContactGroupEntry result) { showStatus("Deleted a contact group.", false); } }, pars); } /** * Retrieve the contact groups feed using the Contacts service and * the contact groupd feed uri. * On success, identify the first group entry with a title starting * with "GWT-Contacts-Client", this is the group that will be deleted. * If no contact group is found, display a message. * Otherwise call deleteContactGroup to delete the group entry. * Alternatively we could also have used deleteContactGroup.deleteEntry to * delete the contact group, but the effect is the same. * * @param contactGroupsFeedUri The contact groups feed uri */ private void getContactGroups(String contactGroupsFeedUri) { showStatus("Loading contact groups feed...", false); service.getContactGroupFeed(contactGroupsFeedUri, new ContactGroupFeedCallback() { public void onFailure(CallErrorException caught) { showStatus( "An error occurred while retrieving the contact groups " + "feed: " + caught.getMessage(), true); } public void onSuccess(ContactGroupFeed result) { ContactGroupEntry[] entries = result.getEntries(); ContactGroupEntry targetGroup = null; for (ContactGroupEntry group : entries) { String title = group.getTitle().getText(); if (title.startsWith("GWT-Contacts-Client")) { targetGroup = group; break; } } if (targetGroup == null) { showStatus("No contacts were found with a title starting with " + "'GWT-Contacts-Client'.", false); } else { String contactGroupEntryUri = targetGroup.getEditLink().getHref(); deleteContactGroup(contactGroupEntryUri, targetGroup.getEtag()); } } }); } /** * 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 = ContactsService.newInstance("HelloGData_Contacts_DeleteContactGroupDemo_v2.0"); if (User.getStatus(scope) == AuthSubStatus.LOGGED_IN) { Button startButton = new Button("Delete a contact group"); startButton.addClickHandler(new ClickHandler() { public void onClick(ClickEvent event) { getContactGroups("http://www.google.com/m8/feeds/groups/default/full"); } }); mainPanel.setWidget(0, 0, startButton); } else { showStatus("You are not logged on to Google Contacts.", true); } } }