Android UnknownHostexception但授予权限

Question

我目前正在开始为Android开发应用程序，但我目前仍然遇到了一个未知的问题。

这是我的代码： ...

protected class FetchWeatherTask extends AsyncTask <String, Void, Void>{
        private final String LOG_TAG = FetchWeatherTask.class.getSimpleName();
        protected Void doInBackground(String... params) {
            //initialize Connection and reader
            HttpURLConnection urlconnection=null;
            BufferedReader reader=null;

            String forecastJsonStr =null;

            String format = "json";
            String units = "metric";
            int numDays = 7;
            try{
                final String BASE_URL = "http://apikey.openweathermap.org/data/2.5/forecast/daily";
                final String QUERY_PARAM="zip";
                final String FORMAT_PARAM= "mode";
                final String UNITS_PARAM= "units";
                final String DAYS_PARAM= "cnt";
                final String APPID_PARAM="APPID";
                //make Connection to the OpenWeatherURL
                //IDEA: API-Code for future use as parameter of the method
                //String apikey = "&APPID="+BuildConfig.OPEN_WEATHER_MAP_API_KEY;
                //String baseUrl="http://apikey.openweathermap.org/data/2.5/forecast/daily?zip=94043&mode=json&units=metric&cnt=7";
                //URL url= new URL(baseUrl.concat(apikey));
                Uri builtUri = Uri.parse(BASE_URL).buildUpon()
                        .appendQueryParameter(QUERY_PARAM,params[0])
                        .appendQueryParameter(FORMAT_PARAM,format)
                        .appendQueryParameter(UNITS_PARAM,units)
                        .appendQueryParameter(DAYS_PARAM,Integer.toString(numDays))
                        .appendQueryParameter(APPID_PARAM,BuildConfig.OPEN_WEATHER_MAP_API_KEY)
                        .build();

                URL url = new URL(builtUri.toString());

                //URL url = new URL("http://apikey.openweathermap.org/data/2.5/forecast/daily?zip=94043&mode=json&units=metric&cnt=7&APPID=31d96db6578ca2e94f31714e882118be");
                Log.v(LOG_TAG, "Built URI "+ builtUri.toString());

                urlconnection= (HttpURLConnection) url.openConnection();
                urlconnection.setRequestMethod("GET");
                urlconnection.connect();

                //Read inputStream into a buffer
                InputStream input = urlconnection.getInputStream();
                StringBuffer buffer= new StringBuffer();
                if(input==null){
                    return null;
                }

                reader = new BufferedReader(new InputStreamReader(input));
                String line;
                while ((line=reader.readLine())!=null){
                    buffer.append(line+"\n");
                }
                if (buffer.length()==0){
                    return null;
                }
                forecastJsonStr=buffer.toString();
            }
            catch(IOException e){
                Log.e("ForecastFragment","Error",e);
                return null;

            }finally {
                if(urlconnection==null){
                    urlconnection.disconnect();
                }
                if(reader!=null){
                    try{
                        reader.close();
                    } catch (IOException e) {
                        Log.e("ForecastFragment","Error",e);
                    }
                }
                return null;
            }

        }
    }

我已经在我的Android清单中为此应用授予了互联网访问权限，但它仍然会导致此异常。这里是manifest.xml用于审查目的：

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.cc_student.sunshine.app">
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>