Retrofit2 访问内部对象数组

Question

我正在尝试从 Json 文件中提取对象列表，但是该文件以一个对象开头，该对象包含我需要的对象数组。我是新来改造这里是我的文件： 接口

public interface OSMApi {

    @Headers({"Accept: application/json"})
    @GET("map")
    Call<List<OSMObject>> getOSMObjects(@Query("bbox") String boxMinMaxLatLon);
}

控制器

public class OSMController implements Callback<List<OSMObject>> {

    static final String BASE_URL = "https://api.openstreetmap.org/api/0.6/";
    private static final String TAG = "OSMController";

    private String bboxLatLon = "//latlongshere";

    public void start(){
        Gson gson = new GsonBuilder()
                .setLenient()
                .create();

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

    OSMApi osmApi = retrofit.create(OSMApi.class);

    Call<List<OSMObject>> call = osmApi.getOSMNodes(bboxLatLon);
    call.enqueue(this);
}

    @Override
    public void onResponse(Call<List<OSMObject>> call, Response<List<OSMObject>> response) {
        if(response.isSuccessful()){
            List<OSMObject> OSMObjectList = response.body();
            OSMObjectList.forEach(OSMObject -> Log.d(TAG, "onResponse: objects "+OSMObject.getId()));
        }else{
            Log.d(TAG, "onResponse: here : "+response.errorBody() + ", "+response.code());
        }
    }

    @Override
    public void onFailure(Call<List<OSMObject>> call, Throwable t) {
        Log.d(TAG, "onFailure: "+ t.getStackTrace() + ", extra: "+ t.getMessage());
    }
}

Json 的开头

{
    "version": "0.6",
    "generator": "CGImap 0.8.3 (652902 spike-07.openstreetmap.org)",
    "copyright": "OpenStreetMap and contributors",
    "attribution": "http://www.openstreetmap.org/copyright",
    "license": "http://opendatacommons.org/licenses/odbl/1-0/",
    "bounds": {
        "minlat": 1.0,
        "minlon": 1.0,
        "maxlat": 1.0,
        "maxlon": 1.0
    },
    "elements": [
        {
            "type": "node",
            "id": 443479273,
            "lat": 1.0,
            "lon": 1.0,
            "timestamp": "2011-04-11T18:06:02Z",
            "version": 3,
            "changeset": 4435725,
            "user": "BeerOfTheTrip",
            "uid": 440880
        },
        {
            "type": "node",
            "id": 443479278,
            "lat": 1.0,
            "lon": 1.0,
            "timestamp": "2011-04-11T18:06:01Z",
            "version": 2,
            "changeset": 4435725,
            "user": "BeerOfTheTrip",
            "uid": 440880
        },
        {
            "type": "node",
            "id": 443479281,
            "lat": 1.0,
            "lon": 1.0,
            "timestamp": "2011-04-11T18:06:01Z",
            "version": 2,
            "changeset": 4435725,
            "user": "BeerOfTheTrip",
            "uid": 440880
        },
etc..........

我的对象Pojo

public class OSMObject implements SerializedName {

    @SerializedName("type")
    @Expose
    private String type;
    @SerializedName("id")
    @Expose
    private int id;
    @SerializedName("lat")
    @Expose
    private double lat;
    @SerializedName("lon")
    @Expose
    private double lon;
    @SerializedName("timestamp")
    @Expose
    private String timestamp;
    @SerializedName("version")
    @Expose
    private int version;
    @SerializedName("changeset")
    @Expose
    private int changeset;
    @SerializedName("uid")
    @Expose
    private int uid;
    @SerializedName("nodes")
    @Expose
    private int[] nodes;

    //Separation
    private ArrayList<OSMNode> OSMNodes = new ArrayList<>();
    private ArrayList<OSMWay> OSMWays = new ArrayList<>();

    public OSMObject(String type, int id, String timestamp, int version, int changeset, int uid, int[] nodes) {
        this.type = type;
        this.id = id;
        this.timestamp = timestamp;
        this.version = version;
        this.changeset = changeset;
        this.uid = uid;
        this.nodes = nodes;
    }

    public OSMObject(String type, int id, double lat, double lon, String timestamp, int version, int changeset, int uid) {
        this.type = type;
        this.id = id;
        this.lat = lat;
        this.lon = lon;
        this.timestamp = timestamp;
        this.version = version;
        this.changeset = changeset;
        this.uid = uid;
    }

+getters and setters....

所以我不需要 jsonObject 中的任何初始信息，我只需要 Elements jsonArray 中的对象列表，这由两个略有不同的对象组成，一个有 Nodes[] 一个没有。因此 pojo 中的 2 个构造函数？

如何设置改造来处理这个问题？目前我遇到的错误是：

onFailure: [Ljava.lang.StackTraceElement;@dbe860f, extra: 预期 BEGIN_ARRAY 但在第 1 行第 2 列路径 $ 处是 BEGIN_OBJECT

补充： 两个不同对象的示例：

        {
            "type": "node",
            "id": 4448646916,
            "lat": 1.0,
            "lon": 1.0,
            "timestamp": "2020-12-21T17:52:35Z",
            "version": 1,
            "changeset": 44211151,
            "user": "Mike Greenwood",
            "uid": 44623152
        },
        {
            "type": "way",
            "id": 44117969,
            "timestamp": "2014-04-11T14:01:16Z",
            "version": 2,
            "changeset": 44627679,
            "user": "Smurfy12",
            "uid": 44220096,
            "nodes": [
                4483345702,
                443479293,
                443479273
            ],
            "tags": {
                "highway": "residential",
                "name": "A Street"
            }
        },

正如您所看到的，它们具有不同的“类型”，一个“节点”和一个“方式”，方式有一个节点数组，而节点有一个“纬度”和“经度”，我不需要担心现在的“标签”。

Answer 1

在“onResponse”中，试试这个：

    if (response.isSuccessful()) {

        JSONObject reader = new JSONObject(response.body());

        List<OSMObject> OSMObjectList = (List<OSMObject>) reader.getJSONArray("elements");

        // now you can work on your "elements" list..

    } else {
        Log.d(TAG, "onResponse: here : " + response.errorBody() + ", " + response.code());
    }

关于 2 个构造函数的注意事项 - 我不确定你如何区分你需要使用哪个构造函数，因为在你的“元素”数组中只有 3 个类似的对象，所以如果你需要帮助 - 请解释您可能在该数组中收到的另一个对象的区别或展示示例。

编辑： 您可以添加新课程并使用它来回复您的回复：

public class JsonResponse {

    private ArrayList<OSMObject> elements;

    public ArrayList<OSMObject> getElements() {
        return elements;
    }
}

在您的 ApiInterface 更改以期望得到回报：

Call<JsonResponse> login...

然后，当您拨打电话时，您可以使用以下方式获取列表：

List<OSMObject> OSMObjectList = response.body().getElements();

所以现在您可以在操作数据之前或之后保存。

Answer 2

解决方案

请像这样更改你的 pojo 类

@Generated("jsonschema2pojo")
public class OSMObject implements Serializable
{

@SerializedName("version")
@Expose
private String version;
@SerializedName("generator")
@Expose
private String generator;
@SerializedName("copyright")
@Expose
private String copyright;
@SerializedName("attribution")
@Expose
private String attribution;
@SerializedName("license")
@Expose
private String license;
@SerializedName("bounds")
@Expose
private Bounds bounds;
@SerializedName("elements")
@Expose
private List<Element> elements = null;
private final static long serialVersionUID = -4976252003298473695L;

public String getVersion() {
return version;
}

public void setVersion(String version) {
this.version = version;
}

public String getGenerator() {
return generator;
}

public void setGenerator(String generator) {
this.generator = generator;
}

public String getCopyright() {
return copyright;
}

public void setCopyright(String copyright) {
this.copyright = copyright;
}

public String getAttribution() {
return attribution;
}

public void setAttribution(String attribution) {
this.attribution = attribution;
}

public String getLicense() {
return license;
}

public void setLicense(String license) {
this.license = license;
}

public Bounds getBounds() {
return bounds;
}

public void setBounds(Bounds bounds) {
this.bounds = bounds;
}

public List<Element> getElements() {
return elements;
}

public void setElements(List<Element> elements) {
this.elements = elements;
}
}

@Generated("jsonschema2pojo")
public class Bounds implements Serializable
{

@SerializedName("minlat")
@Expose
private Float minlat;
@SerializedName("minlon")
@Expose
private Float minlon;
@SerializedName("maxlat")
@Expose
private Float maxlat;
@SerializedName("maxlon")
@Expose
private Float maxlon;
private final static long serialVersionUID = -8105102004947849058L;

public Float getMinlat() {
return minlat;
}

public void setMinlat(Float minlat) {
this.minlat = minlat;
}

public Float getMinlon() {
return minlon;
}

public void setMinlon(Float minlon) {
this.minlon = minlon;
}

public Float getMaxlat() {
return maxlat;
}

public void setMaxlat(Float maxlat) {
this.maxlat = maxlat;
}

public Float getMaxlon() {
return maxlon;
}

public void setMaxlon(Float maxlon) {
this.maxlon = maxlon;
}
}

@Generated("jsonschema2pojo")
public class Element implements Serializable
{

@SerializedName("type")
@Expose
private String type;
@SerializedName("id")
@Expose
private Integer id;
@SerializedName("lat")
@Expose
private Float lat;
@SerializedName("lon")
@Expose
private Float lon;
@SerializedName("timestamp")
@Expose
private String timestamp;
@SerializedName("version")
@Expose
private Integer version;
@SerializedName("changeset")
@Expose
private Integer changeset;
@SerializedName("user")
@Expose
private String user;
@SerializedName("uid")
@Expose
private Integer uid;
private final static long serialVersionUID = 8944398333022644493L;

public String getType() {
return type;
}

public void setType(String type) {
this.type = type;
}

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public Float getLat() {
return lat;
}

public void setLat(Float lat) {
this.lat = lat;
}

public Float getLon() {
return lon;
}

public void setLon(Float lon) {
this.lon = lon;
}

public String getTimestamp() {
return timestamp;
}

public void setTimestamp(String timestamp) {
this.timestamp = timestamp;
}

public Integer getVersion() {
return version;
}

public void setVersion(Integer version) {
this.version = version;
}

public Integer getChangeset() {
return changeset;
}

public void setChangeset(Integer changeset) {
this.changeset = changeset;
}

public String getUser() {
return user;
}

public void setUser(String user) {
this.user = user;
}

public Integer getUid() {
return uid;
}

public void setUid(Integer uid) {
this.uid = uid;
}
}

之后

你已经从 onResponse 方法中得到了 Arrayist

@Override
    public void onResponse(Call<List<OSMObject>> call, Response<List<OSMObject>> response) {
        if(response.isSuccessful()){
            List<OSMObject> OSMObjectList = response.body().getElements();
           Log.d(TAG, "onResponse: here : "+response.body().getElements());
        }else{
            Log.d(TAG, "onResponse: here : "+response.errorBody() + ", "+response.code());
        }
    }

    @Override
    public void onFailure(Call<List<OSMObject>> call, Throwable t) {
        Log.d(TAG, "onFailure: "+ t.getStackTrace() + ", extra: "+ t.getMessage());
    }