如何使用RxJava2和Retrofit2执行POST请求？？

implementation 'io.reactivex.rxjava2:rxjava:2.x.x'
implementation 'io.reactivex.rxjava2:rxandroid:2.x.x'
implementation 'com.squareup.retrofit2:retrofit:2.x.x'
implementation 'com.squareup.retrofit2:converter-gson:2.x.x'

Retrofit retrofit = new Retrofit.Builder()
    .baseUrl("https://api.example.com/")
    .addConverterFactory(GsonConverterFactory.create())
    .build();

public interface ApiService {
    @POST("endpoint")
    Observable<ResponseObject> postData(@Body RequestObject request);
}

public class RequestObject {
    // 请求参数
}

public class ResponseObject {
    // 响应数据
}

ApiService apiService = retrofit.create(ApiService.class);

apiService.postData(requestObject)
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(new Observer<ResponseObject>() {
        @Override
        public void onSubscribe(Disposable d) {
            // 订阅事件
        }

        @Override
        public void onNext(ResponseObject response) {
            // 处理响应数据
        }

        @Override
        public void onError(Throwable e) {
            // 处理错误
        }

        @Override
        public void onComplete() {
            // 请求完成
        }
    });