title: Update Textview right after user change settings value
body: <p>In my app I let the user choose a name to display. It should display as:
  Hello <code>usertext</code>!</p>
  
  <p>I can successfully update settings. I used PreferenceActivity.
  I can change the value too. But to change the text in the selected textview, I have to restart the app.</p>
  
  <p>How can I update my textview right after users update the value in settings?</p>