public void setBackButton() {
   if (mActionBar == null) {
     return;
   }
   // Show home as up, and show an icon.
   final int mask = ActionBar.DISPLAY_HOME_AS_UP | ActionBar.DISPLAY_SHOW_HOME;
   mActionBar.setDisplayOptions(mask, mask);
   mActivity.getActionBar().setHomeButtonEnabled(true);
 }
 /** Removes the back button from being shown */
 public void removeBackButton() {
   if (mActionBar == null) {
     return;
   }
   // Remove the back button but continue showing an icon.
   final int mask = ActionBar.DISPLAY_HOME_AS_UP | ActionBar.DISPLAY_SHOW_HOME;
   mActionBar.setDisplayOptions(ActionBar.DISPLAY_SHOW_HOME, mask);
   mActivity.getActionBar().setHomeButtonEnabled(false);
 }