RxAndroid和翻新版：无法为io.reactivex.Observable创建呼叫适配器>

Question

我正在尝试使用rxJava，rxAndroid，Retrofit2和OkHTTP3从URL端点下载文件。我的代码无法为“ Observable
<retrofit2.Response <okhttp3.ResponseBody

”创建呼叫适配器。这些方法对我来说是陌生的，因此我认为这里缺少一个重要的概念。任何方向或点将不胜感激。

的android.view.View.performClick（View.java:5207）的java：39）的android.os.Handler.handleCallback（Handler.java:746）的android.view.View
$
PerformClick.run（View.java:21168）的）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:148）在android.app.ActivityThread.main（ActivityThread.java:5491）在java.lang
com.android.internal.os.ZygoteInit $
MethodAndArgsCaller.run（ZygoteInit.java:728）的com.android.internal.os.ZygoteInit.main（ZygoteInit.java:618）的.reflect.Method.invoke（本机方法）引起原因：java.lang.IllegalArgumentException：无法找到io.reactivex.Observable>的调用适配器。尝试过：*
retrofit2.adapter.rxjava.RxJavaCallAdapterFactory * retrofit2.ExecutorCallAdapterFactory位于retrofit2.Retrofit.nextCallAdapter（Retrofit.java：

build.gradle：

compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
compile 'io.reactivex.rxjava2:rxjava:2.0.4'
compile 'com.squareup.retrofit2:retrofit:2.1.0'
compile 'com.squareup.retrofit2:adapter-rxjava:2.1.0'

RetrofitInterface.java：

package com.example.khe11e.rxdownloadfile;
import io.reactivex.Observable;
import okhttp3.ResponseBody;
import retrofit2.Call;
import retrofit2.Response;
import retrofit2.http.GET;
import retrofit2.http.Streaming;
import retrofit2.http.Url;

public interface RetrofitInterface {
    // Retrofit 2 GET request for rxjava
    @Streaming
    @GET
    Observable<Response<ResponseBody>> downloadFileByUrlRx(@Url String fileUrl);
}

MainActivity.java：

package com.example.khe11e.rxdownloadfile;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import java.io.File;
import io.reactivex.Observable;
import io.reactivex.ObservableEmitter;
import io.reactivex.ObservableOnSubscribe;
import io.reactivex.Observer;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.disposables.Disposable;
import io.reactivex.functions.Function;
import io.reactivex.schedulers.Schedulers;
import okhttp3.OkHttpClient;
import okhttp3.ResponseBody;
import okio.BufferedSink;
import okio.Okio;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.adapter.rxjava.RxJavaCallAdapterFactory;

public class MainActivity extends AppCompatActivity {

Button downloadImgBtn;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    downloadImgBtn = (Button) findViewById(R.id.downloadImgBtn);
    downloadImgBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            downloadImage();
        }
    });
}

public void downloadImage(){
    RetrofitInterface downloadService = createService(RetrofitInterface.class, "https://www.nasa.gov/");
    downloadService.downloadFileByUrlRx("sites/default/files/iss_1.jpg")
            .flatMap(processResponse())
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(handleResult());
}

public <T> T createService(Class<T> serviceClass, String baseUrl){
    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(baseUrl)
            .client(new OkHttpClient.Builder().build())
            .addCallAdapterFactory(RxJavaCallAdapterFactory.create()).build();
    return retrofit.create(serviceClass);
}

public Function<Response<ResponseBody>, Observable<File>> processResponse(){
    return new Function<Response<ResponseBody>, Observable<File>>() {
        @Override
        public Observable<File> apply(Response<ResponseBody> responseBodyResponse) throws Exception {
            return saveToDiskRx(responseBodyResponse);
        }
    };
}

private Observable<File> saveToDiskRx(final Response<ResponseBody> response){
    return Observable.create(new ObservableOnSubscribe<File>() {
        @Override
        public void subscribe(ObservableEmitter<File> subscriber) throws Exception {
            String header = response.headers().get("Content-Disposition");
            String filename = header.replace("attachment; filename=", "");
            new File("/data/data/" + getPackageName() + "/images").mkdir();
            File destinationFile = new File("/data/data/" + getPackageName() + "/images/" + filename);

            BufferedSink bufferedSink = Okio.buffer(Okio.sink(destinationFile));
            bufferedSink.writeAll(response.body().source());
            bufferedSink.close();

            subscriber.onNext(destinationFile);
            subscriber.onComplete();
        }
    });
}

private Observer<File> handleResult(){
    return new Observer<File>() {
        @Override
        public void onSubscribe(Disposable d) {
            Log.d("OnSubscribe", "OnSubscribe");
        }

        @Override
        public void onNext(File file) {
            Log.d("OnNext", "File downloaded to " + file.getAbsolutePath());
        }

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

        @Override
        public void onComplete() {
            Log.d("OnComplete", "onCompleted");
        }
    };
}
}

我已经尝试过按此处提到的方法添加Call，因此它看起来像：

Call<Observable<Response<ResponseBody>>> downloadFileByUrlRx(@Url String fileUrl);

但是，这会导致flatMap函数出现问题，因为它找不到符号方法flatMap（Function ，Observable \ >）。

Answer 1

您正在使用RxJava 1 适配器进行翻新，将其替换为RxJava 2 变体：

//compile 'com.squareup.retrofit2:adapter-rxjava:2.1.0'
compile 'com.jakewharton.retrofit:retrofit2-rxjava2-adapter:1.0.0'

更新

从Retrofit版本开始，2.2.0存在用于RxJava2的第一方呼叫适配器：

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