public void onNavigateUp(){
  File parentDir=null;
  if (mDirectory != null) {
    parentDir=mDirectory.getParentFile();
  }
  listDirectory(parentDir);
  restoreIndexAndTopPosition();
}

public void onNavigateUp ( ) { File parentDir = null ; if ( mDirectory != null ) { parentDir = mDirectory . getParentFile ( ) ; } listDirectory ( parentDir ) ; restoreIndexAndTopPosition ( ) ; }
call this , when the user presses the up button
