android - JSON 异常和权限

Question

我已经使用开放天气 API 编写了天气应用程序....但是当我在我的手机中安装该应用程序并单击按钮以确定天气时它崩溃了...我在我的手机中使用 Android M

public class DownloadTask extends AsyncTask<String,Void,String>{

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

        String result = "";
        URL url;
        HttpURLConnection httpURLConnection = null;

        try {
            url = new URL(urls[0]);
            httpURLConnection = (HttpURLConnection) url.openConnection();
            InputStream in = httpURLConnection.getInputStream();
            InputStreamReader reader = new InputStreamReader(in);
            int data = reader.read();
            while(data != -1){
                char current = (char) data;
                result += current;

                data = reader.read();
            }
            return result;

        }
        //combined the exceptions MalformedURL and IOException to a common to display a toast msg
        catch (Exception e) {
            e.printStackTrace();
        }

        return null;

    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);

        try {
            String msg = "";
            JSONObject jsonObject = new JSONObject(result);
            String weatherInfo = jsonObject.getString("weather");

            JSONArray arr = new JSONArray(weatherInfo);
            for(int i = 0;i<arr.length();i++){
                JSONObject jsonPart = arr.getJSONObject(i);
                String main = "";
                String desc = "";

                main = jsonPart.getString("main");
                desc = jsonPart.getString("description");
                icon = jsonPart.getString("icon");

                if (main != "" && desc != "") {
                    msg += main + "\r\n" + desc;
                }

            }

            if(msg != ""){
                weatherReport.setText(msg);
            }
            else{
                Toast.makeText(MainActivity.this,
                        "Location not able to determine",Toast.LENGTH_LONG).show();
            }

        } catch (JSONException e) {
            Toast.makeText(MainActivity.this,
                    "Location not able to determine",Toast.LENGTH_LONG).show();
            e.printStackTrace();
        }

    }
}

显示的错误是 arr.length() 应用于空数组....我不明白错误是什么。是关于权限的吗...如果是的话我应该如何在 Marshmallow 中实现权限...这是 onCreate() 中的代码，如果它是关于权限的请告诉如何实现..

try {

                    //to hide the keyboard after pressing the button
                    InputMethodManager manager =
                            (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
                    manager.hideSoftInputFromInputMethod(weatherInput.getWindowToken(),0);

                    DownloadTask downloadTask = new DownloadTask();

                    //used to encode the entered input for url.. for example San Fransisco appears in url
                    //as San%20Fransisco ... and to enable that we use the encoder...
                    String encodedCity = URLEncoder.encode(city,"UTF-8");

                    downloadTask.execute("http://api.openweathermap.org/data/2.5/weather?q=" + encodedCity);

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

日志 ..

02-25 22:56:54.009 1413-1413/com.example.hemantj.weather E/AndroidRuntime: FATAL EXCEPTION: main
                                                                       Process: com.example.hemantj.weather, PID: 1413
                                                                       java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
                                                                           at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
                                                                           at org.json.JSONTokener.nextValue(JSONTokener.java:94)
                                                                           at org.json.JSONObject.<init>(JSONObject.java:156)
                                                                           at org.json.JSONObject.<init>(JSONObject.java:173)
                                                                           at com.example.hemantj.weather.MainActivity$DownloadTask.onPostExecute(MainActivity.java:133)
                                                                           at com.example.hemantj.weather.MainActivity$DownloadTask.onPostExecute(MainActivity.java:92)
                                                                           at android.os.AsyncTask.finish(AsyncTask.java:651)
                                                                           at android.os.AsyncTask.access$500(AsyncTask.java:180)
                                                                           at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:668)
                                                                           at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                           at android.os.Looper.loop(Looper.java:148)
                                                                           at android.app.ActivityThread.main(ActivityThread.java:5451)
                                                                           at java.lang.reflect.Method.invoke(Native Method)
                                                                           at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                           at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Answer 1

 try {
                    Log.d(TAG, "onPostExecute: this inner of post" + getcontent_for_validate);
                    jsonobj = new JSONObject(getcontent_for_validate);
                    System.out.println("this is get content" + jsonobj.toString());


                    JSONArray array = jsonobj.getJSONArray("Staff_Details");
                    for (int i = 0; i < array.length(); i++) {
                        Clint_id = editText_user_name.getText().toString();
                        Api_key = array.getJSONObject(i).getString("api_key");
                       COMPANY_LOGO = array.getJSONObject(i).getString("company_logo");
                        Password = editText_password.getText().toString();
                    }


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

仅限互联网权限

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />