点击URL以获取数据并在列表视图中显示数据

Question

我想了解JSON解析。我想从URL获取数据并在ListView中显示数据，但是我收到错误：

  

不幸的是应用程序停止了

如何解决此错误？我的代码中有错误吗？

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    new JSONTask().execute("14.140.200.186/Hospital/get_city.php");



}
public class JSONTask extends AsyncTask<String,String, List<CityModel>>{
    @Override
    protected void onPostExecute( List<CityModel> result) {
        super.onPostExecute(result);
        CityAdapter adapter=new CityAdapter(getApplicationContext(),R.layout.row,result);
        lvCity = (ListView) findViewById(R.id.lvCity);
        lvCity.setAdapter(adapter);
    }
    public class CityAdapter extends ArrayAdapter{
        private List<CityModel> cityModelList;
        private int resource;
        private LayoutInflater inflater;
        public CityAdapter(Context context, int resource, List<CityModel> objects) {
            super(context, resource, objects);
            cityModelList=objects;
            this.resource=resource;
            inflater= (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            if (convertView==null)
                convertView=inflater.inflate(resource,null);
            TextView cityname;
            cityname= (TextView)convertView.findViewById(R.id.cityname);
            cityname.setText(cityModelList.get(position).getCity_name());

            return  convertView;

        }
    }

    @Override
    protected  List<CityModel> doInBackground(String... params) {
        HttpURLConnection connection = null;
        BufferedReader reader = null;
        try {
            URL url = new URL(params[0]);
            connection = (HttpURLConnection) url.openConnection();
            connection.connect();
            InputStream stream = connection.getInputStream();
            reader = new BufferedReader(new InputStreamReader(stream));
            StringBuffer buffer = new StringBuffer();
            String line = "";
            while ((line = reader.readLine()) != null) {
                buffer.append(line);
            }
            String finalJson=buffer.toString();
            JSONObject parentObject=new JSONObject(finalJson);
            JSONArray parentArray=parentObject.getJSONArray("Cities");
            List<CityModel>cityModelList=new ArrayList<>();
            for (int i=0; i<parentArray.length(); i++){
                JSONObject finalObject = parentArray.getJSONObject(i);
                CityModel cityModel=new CityModel();
                cityModel.setCity_name(finalObject.getString("city_name"));
                cityModelList.add(cityModel);
            }
            return cityModelList;
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (JSONException e) {
            e.printStackTrace();
        } finally {
            if (connection != null)
                connection.disconnect();
            ;
            try {
                if (reader != null)
                    reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }

        }


        return null;
    }
}