title: android converting activities to fragments
body: <p>I have made a nice app with a whole bunch of <code>activities</code> , then i needed a <code>navigation drawer</code> and found out that you need to have only one <code>activity</code> for the whole app and the individual different screens should be <code>fragments</code> that are inserted at runtime.</p>
  
  <p>my question is : </p>
  
  <p>How to convert the entire app to use <code>fragments</code> instead of <code>activities</code> ? (eg: how to preserve activity hierarchy , show a main activity when the user opens the app , different actionbar for each screen , etc...)</p>