code: public void addAction(Action act) {
          if (act.entry != null && act.entry != this) {
              Log.e(TAG, "addAction failed. Already applied to another notification - " +
                    act.entry.ID + ". Current notification is " + ID);
              return;
          }
          if (mActions == null) {
              mActions = new ArrayList<Action>();
          }
          if (mActions.size() == 3) {
              Log.w(TAG, "only suppport up to 3 actions.");
              return;
          }
          act.entry = this;
          mActions.add(act);
      }
docs: Add a action to this notification. Actions are typically displayed as a
  button adjacent to the notification content.
  
  @see android.app.Notification#addAction
  
  @param act