如何修复从LinkedTreeMap到ArrayList的Gson JSON解析？

Question

我正在使用Retrofit + Gson解析JSON。

当我尝试从Google Places API解析响应时（好吧，我不尝试解析，我只是尝试为此响应制作模型）并且我收到了一些错误。

这是来自Google Place API的回复：

    {
   "predictions" : [
      {
         "description" : "Николаевская область, Украина",
         "id" : "3bd747cc4efc2288da48942b909ce18a053c2060",
         "matched_substrings" : [
            {
               "length" : 5,
               "offset" : 0
            }
         ],
         "place_id" : "ChIJydRVsbqaxUARLq1R8Q3RgpM",
         "reference" : "ClRPAAAAwseWiG8NUMt7TqSqz9rMP8R2M4rX7-cMRmIp4OCYL-VdRSr5B5T_PMwWzYOydVStVpYDvm0ldXYPEzxFAuvn1LqhtWHdROhsERwvmx0tVlwSEFdMw0sOe3rDaB2AqKKmF-YaFLvhiEOz3Bklv5-iTa7QQORILVCU",
         "structured_formatting" : {
            "main_text" : "Николаевская область",
            "main_text_matched_substrings" : [
               {
                  "length" : 5,
                  "offset" : 0
               }
            ],
            "secondary_text" : "Украина"
         },
         "terms" : [
            {
               "offset" : 0,
               "value" : "Николаевская область"
            },
            {
               "offset" : 22,
               "value" : "Украина"
            }
         ],
         "types" : [ "administrative_area_level_1", "political", "geocode" ]
      }, ...],
   "status" : "OK"
}

这是我对此回复的模型：

    public class GetGoogleMapPlacesResponse {
    @SerializedName("predictions")
    private List<GooglePlace> googlePlaces;

    public List<GooglePlace> getGooglePlaces() {
        return googlePlaces;
    }

    public void setGooglePlaces(List<GooglePlace> googlePlaces) {
        this.googlePlaces = googlePlaces;
    }
}

但是当Retrofit尝试解析对模型的响应时，我得到错误：

java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap cannot be cast to com.myapp.net.rest.response.GetGoogleMapPlacesResponse

这是调试模式下的原始响应：

Answer 1

您错过了GetGoogleMapPlacesResponse模型的构造函数。

public class GetGoogleMapPlacesResponse {
     private List<GooglePlace> googlePlaces;
     private String status;

     public GetGoogleMapPlacesResponse(List<GooglePlace> googlePlaces, String status) {
         this.googlePlaces = googlePlaces;
         this.status = status;
     }

    ...getters & setters
}

但我强烈建议您使用带有Gson扩展名的AutoValue，然后您的模型将如下所示：

@AutoValue
public abstract class GetGoogleMapPlacesResponse {
      @SerializedName("predictions") public abstract List<GooglePlace> googlePlaces;
      public abstract String status;
}

有关详情，请点击此处：https://github.com/rharter/auto-value-gson