Retrofit2 Android:预计BEGIN_ARRAY但在第1行第2列路径为BEGIN_OBJECT路径$

Question

我知道这不是第一次有人问这个问题,但是使用Retrofit2我无法找到解决问题的正确方法.我按照在线教程进行操作,效果很好.当我将相同的代码应用到我自己的端点时,我得到了这个例外:java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2 path $我不知道如何解决这个问题.

接口:

public interface MyApiService {

// Is this right place to add these headers?
@Headers({"application-id: MY-APPLICATION-ID",
        "secret-key: MY-SECRET-KEY",
        "application-type: REST"})
@GET("Music")
Call<List<Music>> getMusicList();



Retrofit retrofit = new Retrofit.Builder()
        .baseUrl(MySettings.REST_END_POINT)
        .addConverterFactory(GsonConverterFactory.create())
        .build();
}

客户代码:

MyApiService service = MyApiService.retrofit.create(MyApiService.class);
Call<List<Music>> call = service.getMusicList();
call.enqueue(new Callback<List<Music>>() {

    @Override
    public void onResponse(Call<List<Music>> call, Response<List<Music>> response) {
        Log.e("MainActivity", response.body().
    }

    @Override
    public void onFailure(Call<List<Music>> call, Throwable t) {
        Log.e("MainActivity", t.toString());
    }
});

此代码使用此有效负载:

[
{
    "login": "JakeWharton",
    "id": 66577,
    "avatar_url": "https://avatars.githubusercontent.com/u/66577?v=3",
    "gravatar_id": "",
    "url": "https://api.github.com/users/JakeWharton",
    "html_url": "https://github.com/JakeWharton",
    "followers_url": "https://api.github.com/users/JakeWharton/followers",
    "following_url": "https://api.github.com/users/JakeWharton/following{/other_user}",
    "gists_url": "https://api.github.com/users/JakeWharton/gists{/gist_id}",
    "starred_url": "https://api.github.com/users/JakeWharton/starred{/owner}{/repo}",
    "subscriptions_url": "https://api.github.com/users/JakeWharton/subscriptions",
    "organizations_url": "https://api.github.com/users/JakeWharton/orgs",
    "repos_url": "https://api.github.com/users/JakeWharton/repos",
    "events_url": "https://api.github.com/users/JakeWharton/events{/privacy}",
    "received_events_url": "https://api.github.com/users/JakeWharton/received_events",
    "type": "User",
    "site_admin": false,
    "contributions": 741
},
{....

但不是这个:

{
"offset": 0,
"data": [
    {
        "filename": "E743_1458662837071.mp3",
        "created": 1458662854000,
        "publicUrl": "https://api.backendless.com/dbb77803-1ab8-b994-ffd8-65470fa62b00/v1/files/music/E743_1458662837071.mp3",
        "___class": "Music",
        "description": "",
        "likeCount": 0,
        "title": "hej Susanne. ",
        "ownerId": "E743756F-E114-6892-FFE9-BCC8C072E800",
        "updated": null,
        "objectId": "DDD8CB3D-ED66-0D6F-FFA5-B14543ABC800",
        "__meta": "{\"relationRemovalIds\":{},\"selectedProperties\":[\"filename\",\"created\",\"publicUrl\",\"___class\",\"description\",\"likeCount\",\"title\",\"ownerId\",\"updated\",\"objectId\"],\"relatedObjects\":{}}"
    },
    {...

我的音乐班:

public class Music {

   private String ownerId;
   private String filename;
   private String title;
   private String description;
   private String publicUrl;
   private int likeCount;

   // Getters & Setters

}

Answer 1

当你说"这段代码正在使用这个有效载荷:......但不是这个:..."这是预期的,这就是它的工作方式.事实上,错误消息告诉您,在将json转换为java对象时,调用期望json中的数组,但却得到了一个对象.

这个电话:

@GET("Music")
Call<List<Music>> getMusicList();

期望一个Music对象列表,这就是它与json一起工作的原因:

[
  {
    "login": "JakeWharton",
    ...
  },
  ...
]

因为json本身是你的Music对象的数组(Retrofit可以在json数组之间转换为java列表).对于第二个json,你只有一个对象,而不是一个数组(注意缺少[...]).为此,您需要使用映射到该json的另一个模型创建另一个调用.我们假设你已经命名了模型MusicList.这是电话的样子:

@GET("Music")
Call<MusicList> getMusicList();

(请注意,如果要同时保留第一个调用和此调用,则可能需要更改方法名称).

该MusicList模型可能如下所示:

public class MusicList {
  @SerializedName("data")
  private List<Music> musics;
  // ...
}

我假设data数组是一个Music对象列表,但我确实注意到jsons是完全不同的.您可能也需要对此进行调整,但我认为您可以在此处了解相关信息.