android - Retrofit 返回空数组列表，但给出了有效的 POJO 和 Json 来处理(尝试了其他问题，但对它们起作用的答案不在 mne 上)

Question

这里有人知道如何对 Django Rest Framework 项目进行改造吗？我已经按照记录在两端完成了我需要做的一切，它返回了我在 http://www.jsonschema2pojo.org/ 上生成 Pojos 的有效 Json。 ，但出于某种奇怪的原因，Retrofit 不断从给出的 Json 结果中返回一个空列表，我需要它才能生效，所以我明天向我的主管演示我的工作。请帮忙P.S:toast 中的所有内容都显示 0 值、我的 storePlaces arraylist 从中获取数据的列表的大小、storePlaces Arraylist 本身以及 Retrofit 返回的状态代码。希望有用这是我的代码:

API 端点:

// Request method and URL specified in the annotation
// Callback for the parsed response is the last parameter

@GET("/api/products/")
Call<List<Store>> getStoreList(@Query("format") String format);

@GET("/api/stores/{store_id}/")
Call<Store> getClickedStore(@Path("store_id") Integer store_id, @Query("format") String format);

POJO:

public class Store extends RealmObject {

@SerializedName("id")
@Expose
private int id;
@SerializedName("name")
@Expose
private String name;
@SerializedName("picture")
@Expose
private String picture;
@SerializedName("Phone")
@Expose
private String Phone;
@SerializedName("email")
@Expose
private String email;
@SerializedName("website")
@Expose
private String website;
@SerializedName("longitude")
@Expose
private String longitude;
@SerializedName("latitude")
@Expose
private String latitude;
@SerializedName("address")
@Expose
private String address;

/**
 *
 * @return
 *     The id
 */
public int getId() {
    return id;
}

/**
 *
 * @param id
 *     The id
 */
public void setId(int id) {
    this.id = id;
}

/**
 *
 * @return
 *     The name
 */
public String getName() {
    return name;
}

/**
 *
 * @param name
 *     The name
 */
public void setName(String name) {
    this.name = name;
}

/**
 *
 * @return
 *     The picture
 */
public String getPicture() {
    return picture;
}

/**
 *
 * @param picture
 *     The picture
 */
public void setPicture(String picture) {
    this.picture = picture;
}

/**
 *
 * @return
 *     The Phone
 */
public String getPhone() {
    return Phone;
}

/**
 *
 * @param Phone
 *     The Phone
 */
public void setPhone(String Phone) {
    this.Phone = Phone;
}

/**
 *
 * @return
 *     The email
 */
public String getEmail() {
    return email;
}

/**
 *
 * @param email
 *     The email
 */
public void setEmail(String email) {
    this.email = email;
}

/**
 *
 * @return
 *     The website
 */
public String getWebsite() {
    return website;
}

/**
 *
 * @param website
 *     The website
 */
public void setWebsite(String website) {
    this.website = website;
}

/**
 *
 * @return
 *     The longitude
 */
public String getLongitude() {
    return longitude;
}

/**
 *
 * @param longitude
 *     The longitude
 */
public void setLongitude(String longitude) {
    this.longitude = longitude;
}

/**
 *
 * @return
 *     The latitude
 */
public String getLatitude() {
    return latitude;
}

/**
 *
 * @param latitude
 *     The latitude
 */
public void setLatitude(String latitude) {
    this.latitude = latitude;
}

/**
 *
 * @return
 *     The address
 */
public String getAddress() {
    return address;
}

/**
 *
 * @param address
 *     The address
 */
public void setAddress(String address) {
    this.address = address;
}

}

调用Retrofit的方法:

private ArrayList<Store> getDataSet() {

    Gson gson = new GsonBuilder()
            .setExclusionStrategies(new ExclusionStrategy() {
                @Override
                public boolean shouldSkipField(FieldAttributes f) {
                    return f.getDeclaringClass().equals(RealmObject.class);
                }

                @Override
                public boolean shouldSkipClass(Class<?> clazz) {
                    return false;
                }
            })
            .create();

    Retrofit retrofitClient = new Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create(gson))
            .build();

    // create a new service call variable from the interface with retrofitClient
    ShoplistApiEndpointInterface apiService = retrofitClient.create(ShoplistApiEndpointInterface.class);

    //create a new APICall variable of the api interface with its type being that of the call method you'll invoke from the interface
    Call<List<Store>> storeListCall = apiService.getStoreList(FORMAT_SPECIFIER);

    // make the call asynchronously by calling enqueue on the Call type
    //FIXME: chane serverside encoding is option 1 (type:app/json, encoding: utf8)
    storeListCall.enqueue(new Callback<List<Store>>() {

        @Override
        public void onResponse(Call<List<Store>> call, Response<List<Store>> response) {
            // get status code from the HTTP response code
            statusCode = response.code();
            // add the parsed response body data (parsed pojo object list in this case)
            // to the arrayList with the addAll(Collection<type>) method
            List<Store> results = response.body();
            ressize = response.body().size();
            int initialSize = storePlaces.size();
            storePlaces.addAll(initialSize, results);
        }

        @Override
        public void onFailure(Call<List<Store>> call, Throwable t) {
            // log the error here
            Log.e(LOG_TAG, "Failed to download Place list", t);
            Toast.makeText(getActivity(), R.string.failed_to_download_list, Toast.LENGTH_SHORT).show();
        }
    });

    Log.d(LOG_TAG, "Success, new data set is of size " + storePlaces.size() + " with status code: " + statusCode + " from source sized: " + ressize);

    return storePlaces;
}

JSON(从那以后我更新了它以限制用户对他们没有创建的对象具有超过只读的访问权限，所以所有者部分是一个新事物..但是 chrome 的 JSONview 扩展验证了第一个和这个JSON 版本)

   [
{
id: 1,
name: "Shoprite Zm",
picture: "http://127.0.0.1:8000/api/stores/productphotos/stores/serializer_snPGr8P.PNG",
Phone: "0255447854",
email: "fabf@ducj.omf",
website: "http://www.f.rd",
latitude: "0.000000",
longitude: "0.000000",
address: "noiibuiuwefd",
owner: 1
},
{
id: 2,
name: "Game fr",
picture: "http://127.0.0.1:8000/api/stores/productphotos/stores/orcl.PNG",
Phone: "467565",
email: "fnini@irni.nur",
website: "http://afninni.gg.rtd",
latitude: "0.000000",
longitude: "0.000000",
address: "horvsawhgfl,md boisdrl",
owner: 1
},
{
id: 3,
name: "Ret",
picture: null,
Phone: "ajiwenpgoernen",
email: "fihIANPI@FNIIW.VID",
website: "http://FWIHFIFNVOI.fnawifni.afvn9weo.FNWIA",
latitude: "0.000000",
longitude: "0.000000",
address: "fawzsuvba.wfQSFBON",
owner: 1
}
]

(Django 开发服务器控制台输出的最后几个请求是针对我的应用程序的，其余的来自浏览器)

Answer 1

您不能从方法返回异步回调的结果。当方法返回时，您的 storePlaces 始终为空，因为 Retrofit http 调用尚未完成。

解决这个问题的方法是将您自己的回调方法作为 getDataSet() 方法的参数传递。首先定义一个通用的回调接口(interface):

public interface Callback<T> {
    void next(T result);
}

然后更改您的 getDataSet() 方法:

public void getDataSet(Callback<List<Store>> callback) {

    //...

    @Override
    public void onResponse(Call<List<Store>> call, Response<List<Store>> response) {

        // get status code from the HTTP response code
        statusCode = response.code();
        // add the parsed response body data (parsed pojo object list in this case)
        // to the arrayList with the addAll(Collection<type>) method
        List<Store> results = response.body();
        ressize = response.body().size();
        int initialSize = storePlaces.size();
        storePlaces.addAll(initialSize, results);

        callback.next(storePlaces);
    }

    //...
}

现在在您使用 getDataSet 方法的代码中，您可以这样调用它:

getDataSet(new Callback<List<Store>>() {
        @Override
        public void next(List<Store> results) {
            // use the results
        }
    }
)

编辑 简要说明

这是观察者模式的一个例子。

您向Subject(您的Retrofit 运行方法)注册了一个Observer(Callback 接口(interface)的具体实现)。当 Subject 完成它所做的任何任务时，它会通知 Observer 然后运行它的代码。

您可以在需要从中获取结果的异步操作发生的情况下使用此模式。它还在整个 Android 框架中用于注册监听器，例如 OnClickListener。