Question

真的很难将我的Android应用程序连接到具有我需要的JSON的API。我的日志显示JSON进来（即我可以在Android Studio的日志中看到完整的JSON数组），但我的for循环行中出现了nullpointer错误。我知道我应该首先初始化它，但我的JSONArray确实是占位符，直到在另一个类中调用getApartmentList方法。并且直接尝试访问API以在此处为JSONArray提供实际值显然会导致networkonmainthread错误。我可能过于复杂了，但我错过了什么？

 public List<Apartment> getApartmentList(JSONArray jsonArray) { //added the parameter, placeholder for "apartments" array which contains all apts in our database

        List<Apartment> apartmentList = new ArrayList<>();


        for(int i=0; i<jsonArray.length();i++){ //nullpointer exception here

            JSONObject json = null;


            try { 
                json = jsonArray.getJSONObject(i); 


                Apartment apartment = new Apartment(UUID.fromString(json.getString("id") ) ); //UUID from String already converts our JSON string result into a UUID
                apartment.setApartmentText(json.getInt("price") + " " + json.getInt("bedrooms") + " " + json.getInt("bathrooms") );
                apartment.setApartmentLatitude(json.getJSONObject("building").getDouble("latitude"));
                apartment.setApartmentLongitude(json.getJSONObject("building").getDouble("longitude"));


                apartmentList.add(apartment);

            } catch (JSONException e) {
                e.printStackTrace();
            } 


        }//end of for loop 


        return apartmentList;


            }//end of getApartmentList method

这是在单独的类中调用此方法并获得实际值的地方：

public class GetAllCustomerTask extends AsyncTask<ApiConnector,Long,JSONArray>         {
        @Override
        protected JSONArray doInBackground(ApiConnector... params) {    

            return params[0].GetAllCustomers(); 
        }


        //the ApiConnector class is where I connect to the URL of the API, i.e. where i connect to the JSON

     @Override
            protected void onPostExecute(JSONArray jsonArray) {     
ApartmentInventory apartmentInventory = new ApartmentInventory(getActivity() );
apartmentInventory.getApartmentList(jsonArray);
                    }

        } // end of GetAllCustomerTask method

编辑 - 粘贴日志

11-19 22:00:22.787  24528-24528/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example, PID: 24528
    java.lang.NullPointerException
            at ApartmentInventory.getApartmentList(ApartmentInventory.java:118)
            at ListingsFragment$GetAllCustomerTask.onPostExecute(ListingsFragment.java:79)
            at ListingsFragment$GetAllCustomerTask.onPostExecute(ListingsFragment.java:54)
            at android.os.AsyncTask.finish(AsyncTask.java:632)
            at android.os.AsyncTask.access$600(AsyncTask.java:177)
            at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:146)
            at android.app.ActivityThread.main(ActivityThread.java:5487)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
            at dalvik.system.NativeStart.main(Native Method)

NullPointer异常迭代JSONArray for循环

0 个答案: