subscriptionOn，observeOn，Retrofit中的订阅错误

Question

我是retrofit的新手，尽管导入了适当的导入，依赖项，但仍需要通过使用retrofit来调用JSON API。适配器接口已编译。预先感谢！

以下主要活动中有3个错误-

.subscribeOn(Schedulers.newThread())

.observeOn(AndroidSchedulers.mainThread())

和

.subscribe(new Observer<ResponseBody>()
            {
                @Override
                public void onCompleted() { 

这是MainActivity.class

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import com.jakewharton.retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.Observer;
import io.reactivex.schedulers.Schedulers;

import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;
import java.io.IOException;

import java.util.ArrayList;
import okhttp3.ResponseBody;

public class MainActivity extends AppCompatActivity {


public static final String BASE_URL = "http://www.androidbegin.com/tutorial/jsonparsetutorial.txt/";

private RecyclerView mRecyclerView;
String responseString;
private Adapter mAdapter;
private ArrayList<Worldpopulation> List;
JSONObject jsonObject;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    loadJSON();

}


private void loadJSON() {

    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create())
            .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
            .build();

    APInterface apiService = retrofit.create(APInterface.class);
    apiService.getFile(BASE_URL)
            .subscribeOn(Schedulers.newThread())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(new Observer<ResponseBody>()
            {
                @Override
                public void onCompleted() {
                    Log.d("COMPLETE", "COMPLETED TRANSFER");

                }

                @Override
                public void onError(Throwable e)
                {
                    Log.d("ERROR", e.getMessage());
                }

                @Override
                public void onNext(ResponseBody responseBody) {
                    try {
                        responseString = responseBody.string();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }

                    Log.d("SHIZ", responseString);


                    try {
                        jsonObject = new JSONObject(responseString);
                        Log.d("SHIZ", jsonObject.toString());
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }

                    List = new ArrayList<>();
                    //Getting out the world population array
                    JSONArray jsonArray = jsonObject.optJSONArray("worldpopulation");
                    for (int i = 0; i < jsonArray.length(); i++) {
                        Worldpopulation world = new Worldpopulation();
                        JSONObject jsonobject = null;
                        try {
                            jsonobject = jsonArray.getJSONObject(i);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                        try {
                            String rank = jsonobject.getString("rank");
                            world.setRank(Integer.valueOf(rank));
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                        try {
                            String country = jsonobject.getString("country");
                            world.setCountry(country);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                        try {
                            String population = jsonobject.getString("population");
                            Long l = Long.parseLong(population.replaceAll(",", ""));
                            world.setPopulation(l);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                        try {
                            String flag = jsonobject.getString("flag");
                            world.setFlag(flag);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }

                        //adding data to List
                        List.add(world);
                        Log.d("COUNTRY MODEL", List.toString());

                    }

                    //Setting Adapter for RecyclerView
                    Adapter recyclerAdapter = new Adapter(List);
                    RecyclerView.LayoutManager layout = new LinearLayoutManager(MainActivity.this);
                    mRecyclerView.setItemAnimator(new DefaultItemAnimator());
                    mRecyclerView.setLayoutManager(layout);
                    mRecyclerView.setAdapter(recyclerAdapter);
                }
            });
}


}

这是代码中的编译器错误-

  

错误：不是抽象的，并且不会覆盖Observer中的抽象方法onComplete（）

     

错误：方法没有覆盖或实现超类型的方法

     

错误：不兼容的类型：io.reactivex.Scheduler无法转换为rx.Scheduler

这是gradle文件：

    apply plugin: 'com.android.application'
android {
compileSdkVersion 27
defaultConfig {
    applicationId "com.example.shiz.fetchimagerxretro"
    minSdkVersion 15
    targetSdkVersion 27
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}


buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}
}

dependencies {

implementation fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.google.code.gson:gson:2.8.2'
compile 'com.squareup.retrofit2:retrofit:2.4.0'
compile 'com.squareup.retrofit2:converter-gson:2.4.0'
compile 'com.android.support:recyclerview-v7:27.1.1'
compile 'com.squareup.picasso:picasso:2.5.2'
compile 'com.android.support:cardview-v7:27.1.1'
compile 'io.reactivex.rxjava2:rxjava:2.1.17'
compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
compile 'com.squareup.retrofit2:adapter-rxjava:2.4.0'
compile 'com.jakewharton.retrofit:retrofit2-rxjava2-adapter:1.0.0'
implementation 'com.android.support:appcompat-v7:27.1.1'
implementation 'com.android.support.constraint:constraint-layout:1.1.2'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}