Common issue with Android Programming.  The screen rotates and the data disappears.

By default, when the screen is rotated your Activity is killed and restarted.  See the sample code below to save the state

Source:  http://stackoverflow.com/questions/5123407/losing-data-when-rotate-screen

//Use onSaveInstanceState(Bundle) and onRestoreInstanceState

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {

  // Save UI state changes to the savedInstanceState.  
  // This bundle will be passed to onCreate if the process is 
  // killed and restarted.

  savedInstanceState.putBoolean("MyBoolean", true); 
  savedInstanceState.putDouble("myDouble", 1.9); 
  savedInstanceState.putInt("MyInt", 1); 
  savedInstanceState.putString("MyString", "Welcome back to Android");   
  // etc. 
  super.onSaveInstanceState(savedInstanceState); 
} 
//onRestoreInstanceState 
    @Override 
public void onRestoreInstanceState(Bundle savedInstanceState) { 
  super.onRestoreInstanceState(savedInstanceState); 
  // Restore UI state from the savedInstanceState. 
  // This bundle has also been passed to onCreate. 
  boolean myBoolean = savedInstanceState.getBoolean("MyBoolean"); 
  double myDouble = savedInstanceState.getDouble("myDouble"); 
  int myInt = savedInstanceState.getInt("MyInt"); 
  String myString = savedInstanceState.getString("MyString"); 
}