如何使用Retrofit和GSON解析JSON數組？

Question

我已經學習了如何通過Retrofit Gson解析JSON對象，但是我需要通過Retrofit Gson解析完整的JSON數組。

我需要解析以下內容：

"{\n" +
        "  \"snappedPoints\": [\n" +
        "    {\n" +
        "      \"location\": {\n" +
        "        \"latitude\": -35.2784167,\n" +
        "        \"longitude\": 149.1294692\n" +
        "      },\n" +
        "      \"originalIndex\": 0,\n" +
        "      \"placeId\": \"ChIJoR7CemhNFmsRQB9QbW7qABM\"\n" +
        "    },\n" +
        "    {\n" +
        "      \"location\": {\n" +
        "        \"latitude\": -35.280321693840129,\n" +
        "        \"longitude\": 149.12908274880189\n" +
        "      },\n" +
        "      \"originalIndex\": 1,\n" +
        "      \"placeId\": \"ChIJiy6YT2hNFmsRkHZAbW7qABM\"\n" +
        "    },\n" +
        "    {\n" +
        "      \"location\": {\n" +
        "        \"latitude\": -35.280960897210818,\n" +
        "        \"longitude\": 149.1293250692261\n" +
        "      },\n" +
        "      \"originalIndex\": 2,\n" +
        "      \"placeId\": \"ChIJW9R7smlNFmsRMH1AbW7qABM\"\n" +
        "    },\n" +
        "    {\n" +
        "      \"location\": {\n" +
        "        \"latitude\": -35.28142839817933,\n" +
        "        \"longitude\": 149.1298619971291\n" +
        "      },\n" +
        "      \"originalIndex\": 3,\n" +
        "      \"placeId\": \"ChIJy8c0r2lNFmsRQEZUbW7qABM\"\n" +
        "    },\n" +
        "    {\n" +
        "      \"location\": {\n" +
        "        \"latitude\": -35.28193988170618,\n" +
        "        \"longitude\": 149.13001013387623\n" +
        "      },\n" +
        "      \"originalIndex\": 4,\n" +
        "      \"placeId\": \"ChIJ58xCoGlNFmsRUEZUbW7qABM\"\n" +
        "    },\n" +
        "    {\n" +
        "      \"location\": {\n" +
        "        \"latitude\": -35.282819705480151,\n" +
        "        \"longitude\": 149.1295597114644\n" +
        "      },\n" +
        "      \"originalIndex\": 5,\n" +
        "      \"placeId\": \"ChIJabjuhGlNFmsREIxAbW7qABM\"\n" +
        "    },\n" +
        "    {\n" +
        "      \"location\": {\n" +
        "        \"latitude\": -35.283139388422363,\n" +
        "        \"longitude\": 149.12895618087012\n" +
        "      },\n" +
        "      \"originalIndex\": 6,\n" +
        "      \"placeId\": \"ChIJ1Wi6I2pNFmsRQL9GbW7qABM\"\n" +
        "    },\n" +
        "    {\n" +
        "      \"location\": {\n" +
        "        \"latitude\": -35.284728724835304,\n" +
        "        \"longitude\": 149.12835061713685\n" +
        "      },\n" +
        "      \"originalIndex\": 7,\n" +
        "      \"placeId\": \"ChIJW5JAZmpNFmsRegG0-Jc80sM\"\n" +
        "    }\n" +
        "  ]\n" +
        "}"

我只需要緯度和經度。

這是我知道的通過翻新GSON解析JSON對象的方法

package com.example.akshay.retrofitgson;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

/**
 * Created by Akshay on 9/6/2015.
 */
public class gitmodel {
    @SerializedName("latitude")
    @Expose
    public String latitude;
    @SerializedName("longitude")
    @Expose
    public String longitude;

    public void setLatitude(String latitude)
    {
        this.latitude = latitude;
    }
    public String getLatitude()
    {
        return latitude;
    }
    public void setLongitude(String longitude)
    {
        this.longitude = longitude;
    }

    public String getlatitude()
    {
        return  latitude;
    }
}

Answer 1

Retrofit使用Gson庫來序列化Json響應。 只要正確設置了模型類，就可以告訴Gson嘗試將json序列化為該模型類的實例。 您的代碼應類似於以下內容：

String json; // retrieved from file/server
MyObject myObject = new Gson().fromJson(json, MyObject.class)

Answer 2

您可能只需要緯度/經度，但是最簡單的方法是設置POJO以獲取所有內容，然后從POJO中提取緯度/經度。 如果需要，您甚至可以設計反序列化的對象以隱藏內部對象。 對於您的JSON，這非常簡單，只需執行以下操作：

public static class SnappedPoints {
  private List<Point> snappedPoints;

  public String toString() {
    return snappedPoints.toString();
  }
}

public static class Point {
  private Location location;

  public double getLatitude() {
    return location.getLatitude();
  }

  public double getLongitude() {
    return location.getLongitude();
  }

  public String toString() {
    return "{" + location.getLatitude() + "," + location.getLongitude() + "}";
  }
}

public static class Location {
  double latitude;
  double longitude;

  public double getLatitude() {
    return latitude;
  }
  public double getLongitude() {
    return longitude;
  }
}

您只需執行以下操作即可看到實際效果：

public static void main(String[] args) {
  System.out.println(new Gson().fromJson(json, SnappedPoints.class));
}

或者，在翻新的情況下，如下所示：

public interface MyRetrofitAPI {
  @GET("/path/to/json")
  void getSnappedPoints(/* arguments */, Callback<SnappedPoints> callback);
}