ANDROID-MPAndroidChart在json API上显示条形图

我有一本来自英国的教程

但我想用这个

jsonapi

在条上显示值：

 [
  {
    "id_dosen": "3",
    "id_matkul": "2",
    "nilai": "1",
    "jumlah": "18"
  },
  {
    "id_dosen": "3",
    "id_matkul": "2",
    "nilai": "2",
    "jumlah": "2"
  },
  {
    "id_dosen": "3",
    "id_matkul": "2",
    "nilai": "3",
    "jumlah": "7"
  },
  {
    "id_dosen": "3",
    "id_matkul": "2",
    "nilai": "4",
    "jumlah": "6"
  },
  {
    "id_dosen": "3",
    "id_matkul": "2",
    "nilai": "5",
    "jumlah": "3"
  }
]

我已尝试使用此代码来显示：

MainActivity.java

String jsonStr = sh.makeServiceCall(url);

      Log.e(TAG, "Response from url: " + jsonStr);

      if (jsonStr != null) {
        try {
          JSONObject jsonObj = null;
          try {
            jsonObj = new JSONObject(jsonStr);
          } catch (JSONException e) {
            e.printStackTrace();
          }

          // Getting JSON Array node
          JSONArray contacts = jsonObj.getJSONArray("");

          // looping through All Contacts
          for (int i = 0; i < contacts.length(); i++) {
            JSONObject c = contacts.getJSONObject(i);

            String jumlah = c.getString("jumlah");
            String nilai = c.getString("nilai");
            HashMap<String, String> contact = new HashMap<>();

            // adding each child node to HashMap key => value
            contact.put("id", nilai);
            contact.put("name", jumlah);

            // adding contact to contact list
            contactList.add(contact);
          }
        } catch (final JSONException e) {
          Log.e(TAG, "Json parsing error: " + e.getMessage());
          runOnUiThread(new Runnable() {
            @Override
            public void run() {
              Toast.makeText(getApplicationContext(),
                "Json parsing error: " + e.getMessage(),
                Toast.LENGTH_LONG)
                .show();
            }
          });

        }
      } else {
        Log.e(TAG, "Couldn't get json from server.");
        runOnUiThread(new Runnable() {
          @Override
          public void run() {
            Toast.makeText(getApplicationContext(),
              "Couldn't get json from server. Check LogCat for possible errors!",
              Toast.LENGTH_LONG)
              .show();
          }
        });
      }
      return null;
    }

public class HttpHandler {

  private static final String TAG = HttpHandler.class.getSimpleName();

  public HttpHandler() {
  }

  public String makeServiceCall(String reqUrl) {
    String response = null;
    try {
      URL url = new URL(reqUrl);
      HttpURLConnection conn = (HttpURLConnection) url.openConnection();
      conn.setRequestMethod("GET");
      // read the response
      InputStream in = new BufferedInputStream(conn.getInputStream());
      response = convertStreamToString(in);
    } catch (MalformedURLException e) {
      Log.e(TAG, "MalformedURLException: " + e.getMessage());
    } catch (ProtocolException e) {
      Log.e(TAG, "ProtocolException: " + e.getMessage());
    } catch (IOException e) {
      Log.e(TAG, "IOException: " + e.getMessage());
    } catch (Exception e) {
      Log.e(TAG, "Exception: " + e.getMessage());
    }
    return response;
  }

  private String convertStreamToString(InputStream is) {
    BufferedReader reader = new BufferedReader(new InputStreamReader(is));
    StringBuilder sb = new StringBuilder();

    String line;
    try {
      while ((line = reader.readLine()) != null) {
        sb.append(line).append('\n');
      }
    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      try {
        is.close();
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
    return sb.toString();
  }
}

但就我所知，我不知道如何更改

public void AddValuesToBARENTRY（）

，因为我的数据已经存储在

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有人可以帮我修一下。
你们知道怎么解决吗？求你了，伙计们，知道怎么解决吗？请