code: public ResolveInfo getDefaultActivity() {
          synchronized (mInstanceLock) {
              ensureConsistentState();
              if (!mActivities.isEmpty()) {
                  return mActivities.get(0).resolveInfo;
              }
          }
          return null;
      }
docs: Gets the default activity, The default activity is defined as the one
  with highest rank i.e. the first one in the list of activities that can
  handle the intent.
  
  @return The default activity, <code>null</code> id not activities.
  
  @see #getActivity(int)