code: protected final void runOnUiThread(@NonNull Runnable runnable) {
          checkNotNull(runnable, "runnable");
          if (Looper.myLooper() == Looper.getMainLooper()) {
              runnable.run();
          } else {
              mPoster.post(runnable);
          }
      }
docs: Runs a task on the UI thread. If caller thread is the UI thread, the task is executed immediately.