依賴地址

 //http日志攔截器
implementation 'com.squareup.okhttp3:logging-interceptor:4.2.2'

//retrofit核心庫(kù)
    implementation 'com.squareup.retrofit2:retrofit:2.6.2'
//retrofit輔助，gson解析的庫(kù)
    implementation 'com.squareup.retrofit2:converter-gson:2.6.2'

// 必要依賴，和Rxjava結(jié)合必須用到
    implementation 'com.squareup.retrofit2:adapter-rxjava2:2.6.2'
//切換到主線程的依賴
    implementation 'io.reactivex.rxjava2:rxandroid:2.1.1'

ApiService的定義

public interface ApiService {

    @GET("xxxx/xxxxx/xxxxx")
    Observable<School> getSchoolInfo();

    @GET("xxxx/xxxxx/xxxxx")
    Observable<Student> getStudentInfo();
    
    
}

現(xiàn)在模擬場(chǎng)景，先調(diào)用getScholInfo（）接口，獲取結(jié)果后再調(diào)用getStudentInfo（）接口

        final ApiService apiService = retrofit.create(ApiService.class);
       
        apiService.getSchoolInfo().flatMap(new Function<School, ObservableSource<Student>>() {
            @Override
            public ObservableSource<Student> apply(School school) throws Exception {
                //這里可以處理返回的結(jié)果

                return apiService.getStudentInfo();//調(diào)用第二個(gè)接口
            }
        }).subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Consumer<Student>() {
                    @Override
                    public void accept(Student student) throws Exception {
                      //這里可以處理第二個(gè)接口的返回結(jié)果
                    }
                });