值类型org.json.JSONObject无法转换为JSONArray

Question

不确定我在哪里犯了错误。

代码：

public class VaccinationTotalUSA extends Fragment {
RecyclerView rvRecentRecord;
ProgressBar progressBar;
private static final String TAG = VaccinationTotalUSA.class.getSimpleName();
ArrayList<VaccinationTimeline> recentRecords;
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_vaccination, container, false);

// call view
rvRecentRecord = view.findViewById(R.id.vaccinationRecord);
progressBar = view.findViewById(R.id.progress_circular_vaccination);
rvRecentRecord.setLayoutManager(new LinearLayoutManager(getActivity()));
// Volley Fetch
getDataFromServer();
return view;
}
private void showRecyclerView() {
VaccinationAdapter vaccinationAdapter = new VaccinationAdapter(recentRecords);
rvRecentRecord.setAdapter(vaccinationAdapter);
}
private void getDataFromServer() {
String url = "https://disease.sh/v3/covid-19/vaccine/coverage/countries/USA";
recentRecords = new ArrayList<>();
StringRequest stringRequest = new StringRequest(Request.Method.GET, url, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
progressBar.setVisibility(View.GONE);
if (response != null) {
Log.e(TAG, "onResponse:" + response);
try {
JSONObject jsonObject = new JSONObject(response);
JSONArray jsonArray = jsonObject.getJSONArray("timeline");
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject data = jsonArray.getJSONObject(i);
Iterator key = data.keys();
while (key.hasNext()) {
String timedata = key.next().toString();
recentRecords.add(new VaccinationTimeline(key, timedata));
}
}
showRecyclerView();
}catch (JSONException e) {
e.printStackTrace();
}
}
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
progressBar.setVisibility(View.GONE);
Log.e(TAG, "onResponse" + error);
}
});
Volley.newRequestQueue(getActivity()).add(stringRequest);
}

}

JSON:注意：无法在时间线嵌套列表中真正使用jsonObject.getString((，因为每天都会更新所有内容，即2021年4月18日数据进入，2021年3月19日数据将被删除

{
"country": "USA",
"timeline": {
"3/19/21": 118313818,
"3/20/21": 121441497,
"3/21/21": 124481412,
"3/22/21": 126509736,
"3/23/21": 128217029,
"3/24/21": 130473853,
"3/25/21": 133305295,
"3/26/21": 136684688,
"3/27/21": 140180735,
"3/28/21": 143462691,
"3/29/21": 145812835,
"3/30/21": 147602345,
"3/31/21": 150273292,
"4/1/21": 153631404,
"4/2/21": 157606463,
"4/3/21": 161688422,
"4/4/21": 165053746,
"4/5/21": 167187795,
"4/6/21": 168592075,
"4/7/21": 171476655,
"4/8/21": 174879716,
"4/9/21": 178837781,
"4/10/21": 183467709,
"4/11/21": 187047131,
"4/12/21": 189692045,
"4/13/21": 192282781,
"4/14/21": 194791836,
"4/15/21": 198317040,
"4/16/21": 202282923,
"4/17/21": 202282923
}

}

我已经尝试了很多方法来显示这个json数据，有迭代器和没有迭代器。我想使用迭代器，因为我希望能够检索列表名称和列表内部的数据，即4/17/2021:11111111错误输出：

E/VaccinationTotalUSA: onResponse:{"country":"USA","timeline":{"3/19/21":118313818,"3/20/21":121441497,"3/21/21":124481412,"3/22/21":126509736,"3/23/21":128217029,"3/24/21":130473853,"3/25/21":133305295,"3/26/21":136684688,"3/27/21":140180735,"3/28/21":143462691,"3/29/21":145812835,"3/30/21":147602345,"3/31/21":150273292,"4/1/21":153631404,"4/2/21":157606463,"4/3/21":161688422,"4/4/21":165053746,"4/5/21":167187795,"4/6/21":168592075,"4/7/21":171476655,"4/8/21":174879716,"4/9/21":178837781,"4/10/21":183467709,"4/11/21":187047131,"4/12/21":189692045,"4/13/21":192282781,"4/14/21":194791836,"4/15/21":198317040,"4/16/21":202282923,"4/17/21":202282923}}
W/System.err: org.json.JSONException: Value {"country":"USA","timeline":{"3/19/21":118313818,"3/20/21":121441497,"3/21/21":124481412,"3/22/21":126509736,"3/23/21":128217029,"3/24/21":130473853,"3/25/21":133305295,"3/26/21":136684688,"3/27/21":140180735,"3/28/21":143462691,"3/29/21":145812835,"3/30/21":147602345,"3/31/21":150273292,"4/1/21":153631404,"4/2/21":157606463,"4/3/21":161688422,"4/4/21":165053746,"4/5/21":167187795,"4/6/21":168592075,"4/7/21":171476655,"4/8/21":174879716,"4/9/21":178837781,"4/10/21":183467709,"4/11/21":187047131,"4/12/21":189692045,"4/13/21":192282781,"4/14/21":194791836,"4/15/21":198317040,"4/16/21":202282923,"4/17/21":202282923}} of type org.json.JSONObject cannot be converted to JSONArray
at org.json.JSON.typeMismatch(JSON.java:112)
at org.json.JSONArray.<init>(JSONArray.java:96)
at org.json.JSONArray.<init>(JSONArray.java:108)
at com.programming_concept.senior_project.VaccinationTotalUSA$1.onResponse(VaccinationTotalUSA.java:83)
W/System.err:     at com.programming_concept.senior_project.VaccinationTotalUSA$1.onResponse(VaccinationTotalUSA.java:69)
at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:82)
at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:29)
at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:102)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

Answer 1

该JSON中没有数组。在JSON中，数组由方括号([和](表示。JSON中没有方括号。

您有一个外部JSON对象，具有两个属性：country和timeline。timeline是另一个JSON对象，其键基于日期和整数值。

因此，您需要修改您的计划，以便按原样使用JSON，这意味着JSONArray jsonArray = jsonObject.getJSONArray("timeline");需要转换为JSONObject timelineJson = jsonObject.getJSONObject("timeline");。

请注意，有许多更好的JSON解析器可用于Android，例如Moshi。

Answer 2

您正试图设置；时间线"；值转换为CCD_ 8变量，而该值实际上是CCD_。以下是一种可以检索密钥和值的方法：

JSONObject jsonObject = new JSONObject(response);
JSONObject subObject = jsonObject.getJSONObject("timeline");
// Separate the keys into a JSONArray
JSONArray keys = subObject.names();
// Retrieve the keys and values
for(int i=0; i < keys.length(); i++) {
String key = keys.getString(i);
int value = subObject.getInt(key);

Log.d("LOG_TAG", key + " : " + value);
}

Answer 3

您可以尝试以下代码。我已经在Main类本身中对json响应进行了硬编码。此外，我还使用了ObjectMapper，它比使用JsonObject类要好得多

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class AssessmentBridgeApplication {
public static void main(String[] args) throws JsonMappingException, JsonProcessingException {
String json = "{"country":"USA","timeline":{"3/19/21":118313818,"3/20/21":121441497,"3/21/21":124481412,"3/22/21":126509736,"3/23/21":128217029,"3/24/21":130473853,"3/25/21":133305295,"3/26/21":136684688,"3/27/21":140180735,"3/28/21":143462691,"3/29/21":145812835,"3/30/21":147602345,"3/31/21":150273292,"4/1/21":153631404,"4/2/21":157606463,"4/3/21":161688422,"4/4/21":165053746,"4/5/21":167187795,"4/6/21":168592075,"4/7/21":171476655,"4/8/21":174879716,"4/9/21":178837781,"4/10/21":183467709,"4/11/21":187047131,"4/12/21":189692045,"4/13/21":192282781,"4/14/21":194791836,"4/15/21":198317040,"4/16/21":202282923,"4/17/21":202282923}}";
ObjectMapper mapper = new ObjectMapper();
VaccinationRecords vaccinationRecords  = new VaccinationRecords();
vaccinationRecords = mapper.readValue(json, VaccinationRecords.class);
System.out.println(vaccinationRecords.getTimeline());
}
}

=========================

import java.util.Map;
public class VaccinationRecords {
private String country;
Map<String, Object> timeline;
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
public Map<String, Object> getTimeline() {
return timeline;
}
public void setTimeline(Map<String, Object> timeline) {
this.timeline = timeline;
}

}