title: Why is the IWorkspaceRoot I get is null?
body: <p>I am developping an eclipse plugin, but when I use IWorkspaceRoot to get root, it always return null. Do you guys have any ideas about this? Thank you in advance! </p>
  
  <pre><code>IWorkspaceRoot rootWorkspace = ResourcesPlugin.getWorkspace().getRoot();
  </code></pre>