Android Studio Asynchronous method error

Question

I'm trying to make a GET request in Android Studio and I don't understand why this method works in Eclipse as a Java program but not in Android Studio, so I supposed it was something related to threats, so I made a call to an Async Task.
My code looks like this:

Called method:

private static class GetFarmaciasTask extends AsyncTask<String,String,String[][]>{
    protected String[][] doInBackground(String... urls) {
        StringBuilder result = new StringBuilder();
        try {
            URL url = new URL("https://mikelmoli.000webhostapp.com/PHP/json.php");
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = rd.readLine()) != null) {
                result.append(line);
            }
            rd.close();
            JSONObject jsonO = new JSONObject(result.toString());
            //JSONObject myResponse = jsonO.getJSONObject("data");
            JSONArray tsmResponse = (JSONArray) jsonO.get("data");
            String[] indices = {"Nombre", "Provincia", "Poblacion", "Calle", "Numero", "Telefono"};
            String[][] datos = new String[tsmResponse.length()][indices.length];
            for (int i = 0; i < tsmResponse.length(); i++) {
                for (int j = 0; j < indices.length; j++) {
                    datos[i][j] = tsmResponse.getJSONObject(i).getString(indices[j]);
                }
            }
            return datos;
        } catch (IOException e1) {
            e1.printStackTrace();
        } catch (JSONException ej) {
            ej.printStackTrace();
        }
        return null;
    }
}

The error is in this line of the code:

BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));

As I said before, this method works in Eclipse as an independent method.

Some of the errors which made me think about thread errors:

android.os.NetworkOnMainThreadException
Caused by: android.os.NetworkOnMainThreadException

As a side note, if your GET request is REST, have a look at using the retrofit library as it handles background network requests and JSON parsing to your models. — Larry Schiefer, Jun 09 '18 at 13:03

score 1 · Accepted Answer · answered Jun 09 '18 at 13:00

1

This is mostly likely because if the way you are using the AsyncTask. If you are seeing that exception, you are probably calling doInBackground() directly. This article explains how AsyncTask works and should help: http://hiqes.com/androids-asynctask-explained/

Also, they are one time execute objects, so I would recommend not making it static. There are also other subtle pitfalls with making it an inner class of something like an Activity, which can cause memory leaks, so be careful.

answered Jun 09 '18 at 13:00

Larry Schiefer

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I've read the article and it has been very usefull, thanks. Despite this, I'm having trouble with the returned data I need. I call the execute() metod of the class which extends AsyncTask but, how do I get the returned values from the method doInBackground()? May I do it calling onPostExecute? – Mikel Jun 09 '18 at 13:18
You return the data (object) at the end of `doInBackground()`. The `onPostExecute()` method will automatically be called and provide you with the data returned by your `doInBackground()`. You do not call any of the callbacks directly. – Larry Schiefer Jun 09 '18 at 13:25
Thanks, I get it now – Mikel Jun 09 '18 at 13:40

Android Studio Asynchronous method error

1 Answers1