值類型 org.json.JSONObject 無法轉換為 JSONArray

Question

不知道我在哪里犯了錯誤。

代碼：

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：不能真正在時間線嵌套列表上使用 jsonObject.getString()，因為每天都會更新所有內容，即 2021 年 4 月 18 日數據進來，2021 年 3 月 19 日將被刪除

{
"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
}

}

我嘗試了很多方法來顯示這個 json 數據，有和沒有迭代器。 我想使用迭代器，因為我希望能夠在列表中檢索列表名稱和數據，即 2021 年 4 月 17 日：1111111 錯誤 Output：

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

JSON 中沒有數組。 在 JSON 中，數組由方括號（ [和] ）表示。 JSON 中沒有方括號。

您有一個外部 JSON object，具有兩個屬性： country和timeline 。 timeline是另一個 JSON object，其鍵基於整數的日期和值。

因此，您需要修改您的計划以使用 JSON，這意味着JSONArray jsonArray = jsonObject.getJSONArray("timeline"); 需要轉成JSONObject timelineJson = jsonObject.getJSONObject("timeline"); .

請注意，有許多更好的 JSON 解析器可用於 Android，例如Moshi 。

Answer 2

您可以嘗試以下代碼。 我在主 class 本身中硬編碼了 json 響應。 我還使用了 ObjectMapper，它比使用 JsonObject class 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;
}

}

Answer 3

您正在嘗試將“時間線”值設置為JSONArray變量，而該值實際上是JSONObject 。 這是一種可以同時檢索鍵和值的方法：

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);
}