title: Thread hangs when updating ObservableList
body: <p>I am developing a javafx application which has a ListView supported by an ObservableList.</p>
  
  <pre><code>@FXML
  private ListView&lt;String&gt; taggedQueriesResultsList;
  private ObservableList&lt;String&gt; searchResultsList = FXCollections.observableArrayList();
  </code></pre>
  
  <p>The ObservableList is updated with data, say <code>list.add("something")</code>, by a scheduled task using <code>Executors.newSingleThreadScheduledExecutor()</code>. However the scheduled task never runs after the first time. The UI is updated after the first run. I have noticed that if I comment out the line <code>list.add("something")</code> the task runs periodically as scheduled. </p>
  
  <p>I think this is some synchronisation issue but not sure. Please help me understand what is going on and how to resolve the issue.</p>