RxJava请求数据的回调方法在主线程处理

RxJava的Observer的接口回调方法如下：

Subscriber<String> subsciber = new Subscriber<String>() {
    @Override
    public void onCompleted() {
        Log.d("tag", "onCompleted()");
    }
  
    @Override
    public void onError(Throwable e) {
        Log.d("tag", "onError() e=" + e);
    }
  
    @Override
    public void onNext(String s) {
        Log.d("tag", "onNext() data=" + s);
    }
}Subscriber<String>