ウェブAPIからのデータをListViewにセットして表示させる方法

ウェブAPIから取得したデータを配列に格納し、ListViewで表示する方法がわからず困っています。
現状としてはAPIからデータは取得できており、ListViewにアダプターをセットするところまで進んでいるのですが、エミュレーター確認すると、アプリが落ちてしまう状況です。

■MainActivity.java

public class MainActivity extends AppCompatActivity {

    ListView lv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

            HttpResponseAsync asyncTask = new HttpResponseAsync();
            asyncTask.setOnCallBack(new HttpResponseAsync.CallBackTask() {

                private String[] detailWeather;

                @Override
                public void CallBack(String result) {
                    super.CallBack(result);

                    lv = (ListView) findViewById(R.id.listView);

                    result = result.replace("drk7jpweather.callback(", "");
                    result = result.replace(");", "");

                        JSONObject resultJson = new JSONObject(result);
                        JSONArray jsonArray = resultJson.getJSONObject("pref").getJSONObject("area").getJSONArray("info");
                        int count = jsonArray.length();
                        JSONObject[] jsonArrayInfo = new JSONObject[count];

                        String pref = resultJson.getJSONObject("pref").getJSONObject("area").getString("id");

                            for (int i = 0; i < count; i++) {
                                jsonArrayInfo[i] = jsonArray.getJSONObject(i);
                                String date = jsonArrayInfo[i].getString("date");
                                String weather = jsonArrayInfo[i].getString("weather");
                                String maxTemp = jsonArrayInfo[i].getJSONObject("temperature").getJSONArray("range").getJSONObject(0).getString("content");
                                String minTemp = jsonArrayInfo[i].getJSONObject("temperature").getJSONArray("range").getJSONObject(1).getString("content");
                                String total = pref + "\n" + date + "\n天気:" + weather + "\n最高気温:" + maxTemp + "度 最低気温:" + minTemp + "度";

                                detailWeather = new String[7];
                                detailWeather[i] = total;
                            }

                            ArrayAdapter<Object> adapter = new ArrayAdapter<Object>(MainActivity.this, android.R.layout.simple_list_item_1, detailWeather);
                            lv.setAdapter(adapter);
                }
            });
            asyncTask.execute(new URL("http://www.drk7.jp/weather/json/27.js"));
    }
}

■HttpResponseAsync.java

public class HttpResponseAsync extends AsyncTask<URL, Void, String> {

    private CallBackTask callbacktask;

    final StringBuilder result = new StringBuilder();

    int status = 0;

    @Override
    protected String doInBackground(URL... urls) {

        final URL url = urls[0];

        HttpURLConnection HttpUrlConne = null;

            HttpUrlConne = (HttpURLConnection) url.openConnection();

            HttpUrlConne.setRequestMethod("GET");
            HttpUrlConne.setInstanceFollowRedirects(false);
            HttpUrlConne.setDoInput(true);
            HttpUrlConne.setRequestProperty("Accept-language", "jp");

            HttpUrlConne.connect();

            status = HttpUrlConne.getResponseCode();
            if (status == HttpURLConnection.HTTP_OK) {

                    final InputStream inputStream = HttpUrlConne.getInputStream();
                    final String encoding = "UTF-8"; 
                    final InputStreamReader inputReader = new InputStreamReader(inputStream, encoding);

                    final BufferedReader bufferedReader = new BufferedReader(inputReader);

                    String line = null;
                    while ((line = bufferedReader.readLine()) != null) {
                        result.append(line);
                    }

                    bufferedReader.close();
                    inputReader.close();
                    inputStream.close();
            }

        finally {
            if (HttpUrlConne != null) {

                HttpUrlConne.disconnect();

            }
        }

        return result.toString();
    }

    @Override
    protected void onPostExecute(String result) {

        callbacktask.CallBack(result);

    }

    public void setOnCallBack(CallBackTask _cbj) {
        callbacktask = _cbj;
    }


    public static class CallBackTask {
        public void CallBack(String result) {
        }
    }
}

■logcat

04-02 13:57:08.185 2129-2129/com.example.systena.apigetdate E/AndroidRuntime: FATAL EXCEPTION: main
                                                                              Process: com.example.systena.apigetdate, PID: 2129
                                                                              java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
                                                                                  at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
                                                                                  at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
                                                                                  at android.widget.AbsListView.obtainView(AbsListView.java:2344)
                                                                                  at android.widget.ListView.measureHeightOfChildren(ListView.java:1270)
                                                                                  at android.widget.ListView.onMeasure(ListView.java:1182)
                                                                                  at android.view.View.measure(View.java:17430)
                                                                                  at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:727)
                                                                                  at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:463)
                                                                                  at android.view.View.measure(View.java:17430)
                                                                                  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
                                                                                  at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)

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