android - org.json.JSONObject$1 类型的 'json key object' 处的值 null 无法转换为 JSONObject

Question

我正在尝试解析这个 JSON:

{
  "data": [{
  "name": "Griya Legita",
  "is_broken": false,
  "is_repaired": false,
  "is_ok": true,
  "asset_parent": null
},
{
    "name": "4th Floor",
    "is_broken": true,
    "is_repaired": false,
    "is_ok": false,
    "asset_parent": {
      "name": "Buni Building",
      "is_broken": true,
      "is_repaired": false,
      "is_ok": false
    }
  }]
}

此 JSON 在 JSON 数组中有一个 JSON 对象。但是当我调用 JSON 对象时，它说它无法转换。

这是我试过的代码:

class daftarAset extends AsyncTask < String, String, String > {
    @Override
    protected void onPreExecute() {
      super.onPreExecute();
      pDialog = new ProgressDialog(getActivity());
      pDialog.setMessage("LOADING...");
      pDialog.setIndeterminate(false);
      pDialog.setCancelable(true);
      pDialog.show();
    }

    @Override
    protected String doInBackground(String...params) {
      String link_url = "https://example.com/api/assets";
      HttpHandler sh = new HttpHandler();
      String json = sh.makeServiceCall(link_url);

      Log.e(TAG, "Response from url: " + json);
      if (json != null) {
        try {
          JSONObject jsonObject = new JSONObject(json);
          JSONArray data = jsonObject.getJSONArray("data");
          for (int i = 0; i < data.length(); i++) {
            JSONObject ar = data.getJSONObject(i);
            String aset = ar.getString("name");

            JSONObject parent = ar.getJSONObject("asset_parent");
            String nama = parent.getString("name");
            HashMap map = new HashMap();
            map.put(in_aset, aset);
            map.put(in_ruang, nama);
            data_map.add(map);
          }
        } catch (final JSONException e) {
          Log.e(TAG, "Json parsing error: " + e.getMessage());
          getActivity().runOnUiThread(new Runnable() {
            @Override
            public void run() {
              Toast.makeText(getActivity().getApplicationContext(),
                "Json parsing error: " + e.getMessage(),
                Toast.LENGTH_LONG).show();
            }
          });
        }
        getActivity().runOnUiThread(new Runnable() {
          @Override
          public void run() {
            list = (ListView) getView().findViewById(R.id.baik_list);
            adapter = new AssetsAdapter(getActivity(), data_map);
            list.setAdapter(adapter);
            setListViewHeightBasedOnChildren(list);

          }
        });
      }
      return null;
    }

    @Override
    protected void onPostExecute(String s) {
      pDialog.dismiss();
    }

我不知道我的代码出了什么问题。我正在关注 this tutorial我觉得它一定是正确的，但它有一个错误，因为无法转换 JSON。

这是我的错误:

W/System.err: org.json.JSONException: Value null at asset_parent of type org.json.JSONObject$1 cannot be converted to JSONObject
              at org.json.JSON.typeMismatch(JSON.java:100)
              at org.json.JSONObject.getJSONObject(JSONObject.java:613)
              at com.mqa.android.monas.Fragment.BaikFragment$daftarAset.doInBackground(BaikFragment.java:188)
              at com.mqa.android.monas.Fragment.BaikFragment$daftarAset.doInBackground(BaikFragment.java:162)
              at android.os.AsyncTask$2.call(AsyncTask.java:292)
              at java.util.concurrent.FutureTask.run(FutureTask.java:237)
              at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
              at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
              at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
              at java.lang.Thread.run(Thread.java:818)

Answer 1

首先确保JSONObject包含asset_parent键并且对应的键值不为空。然后从 JSONObject 中检索值。

使用此代码:

      JSONObject jsonObject = new JSONObject(json);
      JSONArray data = jsonObject.getJSONArray("data");
      for (int i = 0; i < data.length(); i++) {
        JSONObject ar = data.getJSONObject(i);
        String aset = ar.getString("name");

        HashMap map = new HashMap();
        map.put(in_aset, aset);

        if(ar.has("asset_parent") && !ar.isNull("asset_parent") ){
           JSONObject parent = ar.getJSONObject("asset_parent");
           String name = parent.getString("name");
            map.put(in_ruang, name );
        }else{
             map.put(in_ruang, null );
        }

         Log.i("Test", "Map: " + map.toString()); 
         data_map.add(map); 
          ................ 
          .............
      }

希望它能解决您的问题。如果您的问题已解决，请告诉我。