[Observer 返回空] #RxJava

checkMainThread.java

  public static boolean checkMainThread(Observer<?> observer) {
    if (Looper.myLooper() != Looper.getMainLooper()) {
      observer.onSubscribe(Disposables.empty());
      observer.onError(new IllegalStateException(
          "Expected to be called on the main thread but was " + Thread.currentThread().getName()));
      return false;
    }
    return true;
  }