step3.java

RxView.clicks(button)
        .flatMap(new Func1<Void, Observable<Data>>() {
            @Override
            public Observable<Data> call(Void aVoid) {
                return apiEndpoints
                        .getData()
                        .subscribeOn(Schedulers.io());
            }
        })
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(data ->  displayData(data),              //onNext(Data data)
                   error -> Log.e(TAG, t.getMessage());     //onError(Throwable error)