Android https请求在片段中不起作用

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

private class HttpRequestTask extends AsyncTask<String, Void, String> {
    @Override
    protected String doInBackground(String... params) {
        String urlString = params[0];
        try {
            URL url = new URL(urlString);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            
            // 设置其他请求头参数，如请求头字段、连接超时时间等
            
            InputStream inputStream = connection.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
            StringBuilder response = new StringBuilder();
            String line;
            while ((line = reader.readLine()) != null) {
                response.append(line);
            }
            
            reader.close();
            inputStream.close();
            connection.disconnect();
            
            return response.toString();
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        return null;
    }
    
    @Override
    protected void onPostExecute(String result) {
        // 在此处处理网络请求结果
    }
}

String url = "http://example.com/api";
new HttpRequestTask().execute(url);