android - 如何在 Retrofit 中获取事物列表

Question

有一些关于 Retrofit 的内容我没有理解。我在网上关注示例，但无法编译。我能够通过旧学校(即 HttpGet/HttpResoponse)从 RESTful 服务访问数据，所以我知道该服务有效。它返回一堆 EmployeeData(与仅一个 EmployeeData 相对)

在应用程序 gradle 文件中:

dependencies {
    ...
    compile 'com.google.code.gson:gson:2.7'
    compile 'com.squareup.retrofit2:retrofit:2.1.0'
    compile 'com.squareup.retrofit2:converter-gson:2.1.0'
    ...
}

RESTful 服务端点的 url 是: https://com.somewhere/PhoneDirectoryService/api/Employees/

我已经为基本 url 定义了一个字符串:

<string name="https_phone_directory_service_baseurl">https://com.somewherePhoneDirectoryService/api/</string>

界面

public interface EmployeesService {
    @GET("Employees.json") //  the string in the GET is end part of the endpoint url
    public Call<List<EmployeeEndpointResponse>> listEmployees();
}

回应

public class EmployeeEndpointResponse {

    private List<EmployeeData> employees; // EmployeeData is a POJO

    // public constructor is necessary for collections
    public EmployeeEndpointResponse() {
        employees = new ArrayList<EmployeeData>(); 
    }

    public static EmployeeEndpointResponse parseJSON(String response) {
        GsonBuilder gsonBuilder = new GsonBuilder();
        gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
        Type collectionType = new TypeToken<List<EmployeeData>>(){}.getType();
        Gson gson = gsonBuilder.create();
        EmployeeEndpointResponse employeeEndpointResponse = gson.fromJson(response, EmployeeEndpointResponse.class);
        return employeeEndpointResponse;
    }
}

获取数据

public static boolean getEmployeeData(Context context) {

    Resources resources = context.getResources();
    URI uri = null;
    try {
        uri = new URI(resources.getString(R.string.https_phone_directory_service_baseurl));
    }
    catch (URISyntaxException exception) {
        Log.e("getEmployeeData", exception.toString());
    }

    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(uri.toString())
            .addConverterFactory(GsonConverterFactory.create())
            .build();
    Call<List<EmployeeEndpointResponse>> call = service.listEmployees();

    EmployeesService service = retrofit.create(EmployeesService.class);

    // this does not compile 
    // error: <anonymous com.somewhere.utilities.Utilities$1> is not 
    // abstract and does not override abstract method 
    // onFailure(Call<List<EmployeeEndpointResponse>>,Throwable) in Callback
    call.enqueue(new Callback<List<EmployeeEndpointResponse>>() {
        @Override
        public void onResponse(Response<List<EmployeeEndpointResponse>> response) {
            List<EmployeeEndpointResponse> myList = response.body();
            // Successfull request, do something with the retrieved messages
        }

        @Override
        public void onFailure(Throwable t) {
            // Failed request.
        }
    });

    // so I tried this which gives compile error
    // retrofit2.Callback<java.util.List   
    // <com.somewhere.gson.EmployeeEndpointResponse>>)
    // in Call cannot be applied to anonymous retrofit2.Callback  
    // <com.somewhere.gson.EmployeeEndpointResponse>)         
    call.enqueue(new Callback<EmployeeEndpointResponse>() {
        @Override
        public void onResponse(Call<EmployeeEndpointResponse> call, Response<EmployeeEndpointResponse> response) {
            // handle response here
            EmployeeEndpointResponse employeeEndpointResponse = (EmployeeEndpointResponse)response.body();
        }

        @Override
        public void onFailure(Call<EmployeeEndpointResponse> call, Throwable t) {

        }
    });  

}

我需要做什么？

数据看起来像:

[
{"Name":"Smith, Ken J.",
"Cell":"",
"EmailAddress":"Ken.Smith@somewhere.com",
"Location":"West",
"Phone":"555-555-5555",
"Address":"PO Box 555 5555 Del Norte",
"City":"Jackson",
"State":"WY",
"Zip":"85555",
"Latitude":42.24976,
"Longitude":-107.82171},

{"Name":"Cox, Daniel B.",
"Cell":"",
"EmailAddress":"daniel.cox@somewhere.com",
"Location":"West",
"Phone":"(555) 555-5516",
etc ...}
]

Answer 1

添加依赖

dependencies {
    compile 'com.squareup.okhttp3:okhttp:3.2.0'
    compile 'com.squareup.okhttp3:logging-interceptor:3.2.0'
}

生成http客户端

private static OkHttpClient getOkHttpClient(){
    HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
    logging.setLevel(HttpLoggingInterceptor.Level.NONE);
    OkHttpClient okClient = new OkHttpClient.Builder()
            .addInterceptor(logging)
            .build();
    return okClient;
}

获取数据

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl(YOUR_URL)
        .client(getOkHttpClient())
        .addConverterFactory(GsonConverterFactory.create())
        .build();
return retrofit;


EmployeesService service = retrofit.create(EmployeesService.class);
Call<EmployeeEndpointResponse> call = service.listEmployees();
call.enqueue(new Callback<EmployeeEndpointResponse>() {
        @Override
        public void onResponse(Call<EmployeeEndpointResponse> call, Response<EmployeeEndpointResponse> response) {
            EmployeeEndpointResponse employeeEndpointResponse = response.body();
            //manage your response
        }

        @Override
        public void onFailure(Call<EmployeeEndpointResponse> call, Throwable t) {
        }
    });

解析 JSON

您的 POJO 不需要任何其他方法来解析 JSON。只需使用 http://www.jsonschema2pojo.org/ 生成带有 GSON 注释的代码