title: Exit app when press Back button in activity with multiple fragments in Navigation Drawer
body: <p>I'm working on an app that need Navigation Drawer. This app has 1 MainActivity and about 10 fragments on it. When I click the Navigation Drawer icon in MainActivity it will show the 10 fragments so I can select each of them.</p>
  
  <p>I choose fragment A, then B, then C...to F, for example. When I'm in fragment F and press the Back button, it will take me back to fragment E, then Back again it will take me to fragment D...</p>
  
  <p>My problem is when I'm back to fragment A (from fragment B, of course) and press Back button one more time, it take me to a blank white screen (I think this is the main activity layout). And press Back one more time, the app will exit.</p>
  
  <p>What I want is when I'm back to fragment A (last fragment) and hit Back, the app will exit immediately, not the blank white screen anymore</p>
  
  <p>I've search on SO and found 1 similar question but no answer yet so I have to make another question</p>
  
  <p>How can I do this?
  Thank you very much</p>