title: Android device Back Button close the app not move to Main Activity
body: <p>How can I use the Android back button to move back within my app instead of closing my app?
  this is my activity stack
  Activity A (Main Activity)  OK button press -->Activity B OK button Press  -->Activity C</p>
  
  <p>When i tab the device Back button  it moves to Activity B then again i press the back button app get close (move to android home screen)</p>
  
  <p>I need to go to Main Activity when user back press on Activity B? </p>
  
  <p>NOTE: Im not calling any finish() when moving to next activity..</p>
  
  <p>Sam</p>