Android java.lang.IllegalArgumentException与2

我需要实现简单的例子与改造。我用下一个

渐变依赖性：

compile 'com.squareup.retrofit2:retrofit:2.3.0'
    compile 'com.squareup.retrofit2:converter-gson:2.3.0'
    compile 'com.squareup.retrofit2:adapter-rxjava2:2.3.0'    

接口：

public interface TestService {
        @GET("test")
        Test getUser();
    }

主要活动

button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Retrofit retrofit = new Retrofit.Builder()
                        .baseUrl("http://localhost:8080")
                        .addConverterFactory(GsonConverterFactory.create())
                        .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                        .build();

                TestService service = retrofit.create(TestService.class);
                Test test = service.getUser();
                Log.d("button_click", "test: "+ test);
            }
        });

错误

---

您必须更改界面：

public interface TestService {
    @GET("test")
    Call<Test> getUser(); //Call<Test> instead of just Test
}

及

---

您必须更改界面：

public interface TestService {
    @GET("test")
    Call<Test> getUser(); //Call<Test> instead of just Test
}

及

Response<Test> response = service.getUser().execute();

service.getUser().enqueue(new Callback<Test>() {
    @Override
    public void onResponse(Response<Test> response) {
        //handle successful response
    }

    @Override
    public void onFailure(Throwable t) {
        //handle error
    }
});

public interface TestService {
    @GET("test")
    Observable<Test> getUser();
}

service.getUser().subscribe(
    user -> ,//do something with your user,
    error -> //something wrong happened
);