CloudBackendActivity.java

/*
 * Copyright (c) 2013 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.cloud.backend.android;

import java.util.List;

import android.accounts.AccountManager;
import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;

import com.google.api.client.googleapis.extensions.android.gms.auth.GoogleAccountCredential;

/**
 * An {@link Activity} class that wraps CloudBackend features including CRUD of
 * {@link CloudEntity}, Google account authentication and Google Cloud
 * Messaging. Developer may create a subclass to use these features. If you want
 * to inherit other {@link Activity} subclasses, you may rewrite the superclass
 * name of the class definition below.
 * 
 */
public class CloudBackendActivity extends Activity {

  private static final int REQUEST_ACCOUNT_PICKER = 2;

  private static final String PREF_KEY_ACCOUNT_NAME = "PREF_KEY_ACCOUNT_NAME";

  private GoogleAccountCredential credential;

  private CloudBackendMessaging cloudBackend;

  // is this app subscribed to the Cloud Message?
  private static boolean isSubscribedToBroadcastMessage = false;

  /**
   * Returns {@link CloudBackendMessaging} instance for this activity.
   * 
   * @return {@link CloudBackendMessaging}
   */
  protected CloudBackendMessaging getCloudBackend() {
    return cloudBackend;
  }

  /**
   * Subclasses may override this to return false if the app need to disable
   * authentication.
   */
  public boolean isAuthEnabled() {
    return Consts.IS_AUTH_ENABLED;
  }

  /**
   * Subclasses may override this to execute initialization of the activity. If
   * it uses any CloudBackend features, it should be executed inside
   * {@link #onPostCreate()} that will be called after CloudBackend
   * initializations such as user authentication.
   */
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // init backend
    cloudBackend = new CloudBackendMessaging(this);

    // create credential
    credential = GoogleAccountCredential.usingAudience(this, Consts.AUTH_AUDIENCE);
    cloudBackend.setCredential(credential);

    // if auth enabled, get account name from the shared pref
    if (isAuthEnabled()) {
      String accountName = cloudBackend.getSharedPreferences().getString(PREF_KEY_ACCOUNT_NAME,
          null);
      if (accountName == null) {
        // let user pick an account
        super.startActivityForResult(credential.newChooseAccountIntent(), REQUEST_ACCOUNT_PICKER);
        return; // continue init in onActivityResult
      } else {
        credential.setSelectedAccountName(accountName);
      }
    }

    // post create initialization
    _onPostCreate();
  }

  private void _onPostCreate() {

    // init subscription to broadcast message
    if (!isSubscribedToBroadcastMessage) {
      isSubscribedToBroadcastMessage = true;
      CloudCallbackHandler<List<CloudEntity>> handler = new CloudCallbackHandler<List<CloudEntity>>() {
        @Override
        public void onComplete(List<CloudEntity> results) {
          onBroadcastMessageReceived(results);
        }
      };
      cloudBackend.subscribeToCloudMessage(CloudBackendMessaging.TOPIC_ID_BROADCAST, handler);
    }

    // call onPostCreate
    this.onPostCreate();
  }

  /**
   * Will be called after initialization process including the account picking.
   * Subclasses may override to execute any initialization of the activity.
   */
  protected void onPostCreate() {
  }

  /**
   * Handles broadcast messages from the backend. Subclasses may override this
   * to handle the message accordingly.
   * 
   * @param message
   *          {@link CloudEntity} that contains the message values.
   */
  public void onBroadcastMessageReceived(List<CloudEntity> message) {
  }

  /**
   * Handles callback from Intents like authorization request or account
   * picking.
   */
  @Override
  protected final void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    switch (requestCode) {
    case REQUEST_ACCOUNT_PICKER:
      if (data != null && data.getExtras() != null) {

        // set the picked account name to the credential
        String accountName = data.getStringExtra(AccountManager.KEY_ACCOUNT_NAME);
        credential.setSelectedAccountName(accountName);

        // save account name to shared pref
        SharedPreferences.Editor e = cloudBackend.getSharedPreferences().edit();
        e.putString(PREF_KEY_ACCOUNT_NAME, accountName);
        e.commit();
      }

      // post create initialization
      _onPostCreate();
      break;
    }
  }

  /**
   * Returns account name selected by user, or null if any account is selected.
   */
  protected String getAccountName() {
    return credential == null ? null : credential.getSelectedAccountName();
  }
}