Fix based on Sandor's comments

MyTracks/src/com/google/android/apps/mytracks/MyTracksApplication.java

@@ -1,5 +1,18 @@
-// Copyright 2011 Google Inc. All Rights Reserved.
-
+/*
+ * 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.android.apps.mytracks;
 
 import com.google.android.apps.mytracks.content.TrackDataHub;
@@ -8,24 +21,25 @@ import android.app.Application;
 
 /**
  * MyTracksApplication for keeping global state.
- * 
- * @author jshih@google.com (Jimmy Shih)
  *
+ * @author jshih@google.com (Jimmy Shih)
  */
 public class MyTracksApplication extends Application {
+
   private TrackDataHub trackDataHub;
 
   /**
    * Gets the application's TrackDataHub.
    * 
+   * Note: use synchronized to make sure only one instance is created per application.
    */
-  public TrackDataHub getTrackDataHub() {
-    if (trackDataHub == null) {     
+  public synchronized TrackDataHub getTrackDataHub() {
+    if (trackDataHub == null) {
       trackDataHub = TrackDataHub.newInstance(getApplicationContext());
     }
     return trackDataHub;
   }
-  
+
   public void clearTrackDataHub() {
     trackDataHub = null;
   }