空指针异常，改造? [英] Null-pointer Exception, Retrofit?

问题描述

我正在尝试从 URL 获取 id 但获取空指针异常

I am trying to get an id from URL but getting the null pointer exception

java.lang.NullPointerException:尝试从空对象引用上的字段java.lang.String com.hex.encode.ID_Model$User.id"读取在 com.hex.encode.Home$3.onResponse(Home.java:99)

java.lang.NullPointerException: Attempt to read from field 'java.lang.String com.hex.encode.ID_Model$User.id' on a null object reference at com.hex.encode.Home$3.onResponse(Home.java:99)

这是我用来获取 ID 的代码:

and this is the code I am using to get the id:

private void GetID() {
        Call<ID_Model> idcall = fetchdata.getIdService().getID(user_search);
        idcall.enqueue(new Callback<ID_Model>() {
            @Override
            public void onResponse(@NonNull Call<ID_Model> call,@NonNull Response<ID_Model> response) {
                assert response.body() != null;
                String fetched_id =response.body().getUser().getId;//this is where the exception is poping
                GetData(fetched_id);
            }

            @Override
            public void onFailure(@NonNull Call<ID_Model> call, @NonNull Throwable t) {
                //something//
            }
        });
    } 

以下是 fetchdata 类:

and below is the fetchdata class:

class fetchdata {
    private static UserFetchData userdatafetch = null;
    private static UserIDFetch fetchService = null;

    static  UserIDFetch getIdService() {
        if (fetchService == null) {
            String id_url = "url_and_it's_working";
            Retrofit fetch_id = new Retrofit.Builder()
                    .baseUrl(id_url)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
            fetchService = fetch_id.create(UserIDFetch.class);
        }
        return fetchService;
    }

    public interface UserIDFetch{
        @GET("{user_input}"+"/")
        Call<ID_Model> getID(@Path("user_input") String s);
    }
}

编辑

这是 Id_Model :

Here is the Id_Model :

public class ID_Model {

    @SerializedName("user")
    @Expose
    public User user;

    public User getUser() {
        return user;
    }

    public class User {

        @SerializedName("id")
        @Expose
        public String id;

        public String getId() {
            return id;
        }
        public void setId(String id) {
            this.id = id;
        }

    }
}

编辑这是来自 API 服务器的响应:https://justpaste.it/4gk8r

Edit Here is the response from the API Server : https://justpaste.it/4gk8r

推荐答案

您需要使用 response.isSucessful() 检查响应是否成功.这也取决于服务器端，当 API 成功命中服务器时，他们发送 200 然后我们需要检查 API 响应是否success 或 failure 基于响应.

You need to check response is successful with response.isSucessful(). And it also depends on server side they send the 200 when API successfully hit on server and then we need to check the API response is it success or failure on the basis of the response.

在你的情况下，我认为 API 调用是成功的 200 并返回一些响应但 response.body().getUser()是 null.所以你必须检查API的响应.

In your case, I think API call is success with 200 and return some response but response.body().getUser() is null. So you have to check the response of API.

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