Java tutorial
/** * Copyright 2014 Google Inc. All rights reserved. * * 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.samples.apps.iosched.sync.userdata.http; import android.content.Context; import android.text.TextUtils; import android.util.Log; import com.google.api.client.extensions.android.http.AndroidHttp; import com.google.api.client.googleapis.extensions.android.gms.auth.GoogleAccountCredential; import com.google.api.client.googleapis.extensions.android.gms.auth.UserRecoverableAuthIOException; import com.google.api.client.json.gson.GsonFactory; import com.google.api.services.drive.Drive; import com.google.api.services.drive.DriveScopes; import com.google.samples.apps.iosched.sync.SyncHelper; import com.google.samples.apps.iosched.sync.userdata.AbstractUserDataSyncHelper; import com.google.samples.apps.iosched.sync.userdata.UserAction; import com.google.samples.apps.iosched.sync.userdata.util.UserDataHelper; import com.google.samples.apps.iosched.util.AccountUtils; import java.io.IOException; import java.util.HashSet; import java.util.List; import java.util.Set; import static com.google.samples.apps.iosched.util.LogUtils.LOGD; import static com.google.samples.apps.iosched.util.LogUtils.makeLogTag; /** * Helper class that syncs starred sessions data with Drive's AppData folder using direct * HTTP Drive API through google-api-client library. * * Based on https://github.com/googledrive/appdatapreferences-android */ public class HTTPUserDataSyncHelper extends AbstractUserDataSyncHelper { private static final String GCM_KEY_PREFIX = "GCM:"; private GoogleAccountCredential mCredentials; /** * Private {@code HTTPUserDataSyncHelper} constructor. * @param context Context of the application */ public HTTPUserDataSyncHelper(Context context, String accountName) { super(context, accountName); mCredentials = GoogleAccountCredential.usingOAuth2(mContext, java.util.Arrays.asList(DriveScopes.DRIVE_APPDATA)); mCredentials.setSelectedAccountName(mAccountName); } private String extractGcmKey(Set<String> remote) { String remoteGcmKey = null; Set<String> toRemove = new HashSet<String>(); for (String s : remote) { if (s.startsWith(GCM_KEY_PREFIX)) { toRemove.add(s); remoteGcmKey = s.substring(GCM_KEY_PREFIX.length()); LOGD(TAG, "Remote data came with GCM key: " + AccountUtils.sanitizeGcmKey(remoteGcmKey)); } } for (String s : toRemove) { remote.remove(s); } return remoteGcmKey; } /** * Syncs the preferences file with an appdata preferences file. * * Synchronization steps: * 1. If there are local changes, sync the latest local version with remote * and ignore merge conflicts. The last write wins. * 2. If there are no local changes, fetch the latest remote version. If * it includes changes, notify that preferences have changed. */ protected boolean syncImpl(List<UserAction> actions, boolean hasPendingLocalData) { try { LOGD(TAG, "Now syncing user data."); Set<String> remote = UserDataHelper.fromString(fetchRemote()); Set<String> local = UserDataHelper.getSessionIDs(actions); String remoteGcmKey = extractGcmKey(remote); String localGcmKey = AccountUtils.getGcmKey(mContext, mAccountName); LOGD(TAG, "Local GCM key: " + AccountUtils.sanitizeGcmKey(localGcmKey)); LOGD(TAG, "Remote GCM key: " + (remoteGcmKey == null ? "(null)" : AccountUtils.sanitizeGcmKey(remoteGcmKey))); // if the remote data came with a GCM key, it should override ours if (!TextUtils.isEmpty(remoteGcmKey)) { if (remoteGcmKey.equals(localGcmKey)) { LOGD(TAG, "Remote GCM key is the same as local, so no action necessary."); } else { LOGD(TAG, "Remote GCM key is different from local. OVERRIDING local."); localGcmKey = remoteGcmKey; AccountUtils.setGcmKey(mContext, mAccountName, localGcmKey); } } // If remote data is the same as local, and the remote end already has a GCM key, // there is nothing we need to do. if (remote.equals(local) && !TextUtils.isEmpty(remoteGcmKey)) { LOGD(TAG, "Update is not needed (local is same as remote, and remote has key)"); return false; } Set<String> merged; if (hasPendingLocalData || TextUtils.isEmpty(remoteGcmKey)) { // merge local dirty actions into remote content if (hasPendingLocalData) { LOGD(TAG, "Has pending local data, merging."); merged = mergeDirtyActions(actions, remote); } else { LOGD(TAG, "No pending local data, just updating remote GCM key."); merged = remote; } // add the GCM key special item merged.add(GCM_KEY_PREFIX + localGcmKey); // save to remote LOGD(TAG, "Sending user data to Drive, gcm key " + AccountUtils.sanitizeGcmKey(localGcmKey)); new UpdateFileDriveTask(getDriveService()).execute(UserDataHelper.toSessionsString(merged)); } else { merged = remote; } UserDataHelper.setLocalStarredSessions(mContext, merged, mAccountName); return true; } catch (IOException e) { handleException(e); } return false; } /** * Constructs a Drive service in the current context and with the * credentials use to initiate AppdataPreferences instance. * @return Drive service instance. */ public Drive getDriveService() { Drive service = new Drive.Builder(AndroidHttp.newCompatibleTransport(), new GsonFactory(), mCredentials) .setApplicationName(mContext.getApplicationInfo().name).build(); return service; } /** * Updates the remote preferences file with the given JSON content. * @throws IOException */ private Set<String> mergeDirtyActions(List<UserAction> actions, Set<String> starredSessions) throws IOException { // apply "dirty" actions: for (UserAction action : actions) { if (action.requiresSync) { if (UserAction.TYPE.ADD_STAR.equals(action.type)) { starredSessions.add(action.sessionId); } else { starredSessions.remove(action.sessionId); } } } return starredSessions; } /** * Fetches the remote file. * @throws IOException */ private String fetchRemote() throws IOException { String json = new GetOrCreateFIleDriveTask(getDriveService()).execute(); Log.v(TAG, "Got this content from remote myschedule: [" + json + "]"); return json; } /** * Handles API exceptions and notifies OnExceptionListener * if given exception is a UserRecoverableAuthIOException. * @param exception Exception to handle */ private void handleException(Exception exception) { Log.e(TAG, "Could not sync myschedule", exception); if (exception != null && exception instanceof UserRecoverableAuthIOException) { throw new SyncHelper.AuthException(); } } private static final String TAG = makeLogTag(HTTPUserDataSyncHelper.class); }