Android无法解析rxjava中的订阅方法

Question

Im tring to use rxjava with retrofit in android studio. In fact i followed this https://code.tutsplus.com/tutorials/getting-started-with-retrofit-2--cms-27792 tutorial This is what everything that I did:

compile 'com.android.support:appcompat-v7:25.1.0'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    testCompile 'junit:junit:4.12'
    compile 'com.squareup.retrofit2:retrofit:2.2.0'
    compile 'com.google.code.gson:gson:2.8.0'
    compile 'com.squareup.retrofit2:converter-gson:2.2.0'
    compile 'com.android.support:recyclerview-v7:25.1.0'
    compile 'com.squareup.retrofit2:adapter-rxjava2:2.2.0'
    compile 'io.reactivex.rxjava2:rxjava:2.0.9'
    compile 'io.reactivex:rxandroid:1.2.1'
    compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
    compile 'com.jakewharton.retrofit:retrofit2-rxjava2-adapter:1.0.0'

And i created Retrofit client and Interface subscribe method. It says cann't be resolve

mService.getAnswer().subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread())
             .subscribe(new Subscriber<SOAnswersResponse>() {
                            @Override
                            public void onCompleted() {

                            }

                            @Override
                            public void onError(Throwable e) {

                            }

                            @Override
                            public void onNext(SOAnswersResponse soAnswersResponse) {

                            }


       }
         );

I imported this in my main activity:

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.DividerItemDecoration;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;

import android.widget.Toast;

import com.example.android.stackoverflow.Data.Model.Item;

import com.example.android.stackoverflow.Data.Model.SOAnswersResponse;
import com.example.android.stackoverflow.Data.remote.ApiUtils;
import com.example.android.stackoverflow.Data.remote.SOService;


import java.util.ArrayList;


import io.reactivex.schedulers.Schedulers;
import io.reactivex.android.schedulers.AndroidSchedulers;
import rx.Subscriber;

Answer 1

Rxplanation :

In the tutorial You have linked was used RxJava 1. In RxJava 2 method subscribe does not accept Subscriber class instances as arguments. You have to use:

• for Single : Consumer , BiConsumer , SingleObserver ,

• for Observable : Consumer , Action , Observer ,

• for Maybe : Consumer , Action , MaybeObserver ,

• for Flowable : Consumer , Action , FlowableSubscriber ,

• for Completable : Consumer , Action , CompletableObserver ,

All above mentioned operators have also subscribe() method without arguments.

Clean-ups

You have some kind of mess in your dependencies. Shortest list of dependencies I can come up with is:

// Reactive extensions.
compile 'io.reactivex.rxjava2:rxjava:2.1.0'
compile 'io.reactivex.rxjava2:rxandroid:2.0.1'

// Networking.
compile 'com.squareup.retrofit2:retrofit:2.2.0'
compile 'com.squareup.retrofit2:converter-jackson:2.2.0'
compile 'com.squareup.retrofit2:adapter-rxjava2:2.2.0'

Especially, please do not use two different versions of RxAndroid or adapters as you have done:

compile 'io.reactivex:rxandroid:1.2.1'
compile 'io.reactivex.rxjava2:rxandroid:2.0.1'

compile 'com.squareup.retrofit2:adapter-rxjava2:2.2.0'
compile 'com.jakewharton.retrofit:retrofit2-rxjava2-adapter:1.0.0'

There is also no need to use of Jake Wharton's adapter as it is deprecated. Square has prepared adapter for RxJava2:

compile 'com.squareup.retrofit2:adapter-rxjava2:2.2.0'

Sample code

Now, when everything is configured, domain model can look like:

package com.todev.rxretrofit;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonInclude;

import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(value = NON_NULL)
class Song {

  private String id;

  private String title;

  public String getId() {
    return id;
  }

  public String getTitle() {
    return title;
  }
}

Keep in mind I used Jackson (as it is simpler to use IMHO). Do not hesitate to use GSON annotations but be awere of that You will have to change Jackson dependency to GSON and reconfigure Retrofit service instance construction.

Simple service interface:

package com.todev.rxretrofit;

import io.reactivex.Single;
import java.util.Collection;
import retrofit2.http.GET;

interface CustomService {

  @GET("songs")
  Single<Collection<Song>> getAllSongs();
}

And last (but not least) usage in activity (I included all imports on purpose):

package com.todev.rxretrofit;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.annotations.NonNull;
import io.reactivex.disposables.CompositeDisposable;
import io.reactivex.functions.Consumer;
import io.reactivex.schedulers.Schedulers;
import java.util.Collection;
import okhttp3.OkHttpClient;
import retrofit2.Retrofit;
import retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory;
import retrofit2.converter.jackson.JacksonConverterFactory;

public class MainActivity extends AppCompatActivity {

  private CustomService customService = new Retrofit.Builder()
      .baseUrl("http://<api_address>:<api_port>/")
      .addConverterFactory(JacksonConverterFactory.create())
      .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
      .client(new OkHttpClient.Builder().build())
      .build()
      .create(CustomService.class);

  private CompositeDisposable disposables = new CompositeDisposable();

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

    this.disposables.add(
        this.customService.getAllSongs()
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(this.responseHandler, this.errorHandler));
  }

  @Override
  protected void onDestroy() {
    this.disposables.dispose();
    super.onDestroy();
  }

  private Consumer<Collection<Song>> responseHandler = new Consumer<Collection<Song>>() {
    @Override
    public void accept(Collection<Song> songs) throws Exception {
      // TODO: Handle response.
      for (Song song : songs) {
        Log.d(this.getClass().getSimpleName(), String.valueOf(song));
      }
    }
  };

  private Consumer<Throwable> errorHandler = new Consumer<Throwable>() {
    @Override
    public void accept(@NonNull Throwable throwable) throws Exception {
      // TODO: Handle error.
      Log.d(this.getClass().getSimpleName(), throwable.getLocalizedMessage());
    }
  };
}

As you can see I used Consumer s. You can also use lambda expressions and use class methods instead.

Notice

JSON document used in this example was served by json-server from simple text file:

[
  {
    "id": 0,
    "title": "Song of Fire and Ice"  
  },
  {
    "id": 1,
    "title": "The Hanging Tree"
  }
]

Post scriptum

Remember to add Internet permission in your Manifest:

<uses-permission android:name="android.permission.INTERNET"/>

Otherwise you will receive SocketException with cause:

android.system.ErrnoException: socket failed: EACCES (Permission denied)

Answer 2

you should add below 3 libraries

implementation 'com.squareup.retrofit2:retrofit:2.6.1'
implementation 'com.squareup.retrofit2:converter-gson:2.6.1'
implementation 'com.squareup.retrofit2:adapter-rxjava2:2.2.0'
implementation 'io.reactivex.rxjava2:rxandroid:2.1.0'