Networking stuff tends to brick up, since responses can take a while to travel. What it’s saying is that you need to move your code to another thread so that your program doesn’t freeze up while it’s waiting for a response.

This won’t prevent networking-related slowdowns, but it will get rid of the error:

Thread networking = new Thread(){
    void run() {
        int responseCode = con.getResponseCode();
    }
}
networking.start();
networking.join();

I was trying to write an app which gets some JSON from a website, converts it into an array and then puts specific elements of this array into different spots of a table in the app. I wrote the code which gets me the JSON data and converts it into an ArrayList in Eclipse. It worked great there. I now tried to implement the code in Android Studio but I just can’t get it to work. I have the following code:

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.table_layout);
        TextView textview = (TextView) findViewById(R.id.textView8);
        try{
            textview.setText(MainActivity.get_data().toString());
        }
        catch (Exception e){
            textview.setText(e.getClass().getCanonicalName());
        }
    }

    public static ArrayList<String> get_data() throws Exception{
        String[] ids = new String[] {(here are some ids)};
        ArrayList<String> alldata = new ArrayList<>();
        for(int r=0;r<ids.length;r++) {
            String url = "https://ktrax.kisstech.ch/backend/tracking?db=aviation&sw_lat=40.97765930663377&sw_lon=-26.280096606906117&ne_lat=43.01854550507729&ne_lon=-23.407171802218617&ktrax_id=icao%3a" +ids[r]+"&format=json";
            URL ktraxURL = new URL(url);
            JSONArray test = Networkaccess.getJSONarr(ktraxURL);
            ArrayList<String> listdata = MainActivity.converter(test);
            ArrayList<String> elementlist = new ArrayList<>();
            (some more code (irrelevant in this matter) which makes the array nice and neat)

        //System.out.println(alldata);
        return alldata;
    }

    public static ArrayList<String> converter(JSONArray test){ //creates an array with all the data splited 

    (Some code that converts JSON to ArrayList (also no problems here))
    }
}

class Networkaccess{
    public static JSONArray getJSONarr(URL ktraxURL) throws Exception{
        HttpURLConnection con = (HttpURLConnection) ktraxURL.openConnection();
        //Checking for reponse code of GET Method
        con.setRequestMethod("GET");


!!!!!!     int responseCode = con.getResponseCode(); //THE DEBUGGER JUMPS FROM HERE TO THE CATCH IN MAIN



        System.out.println("Response Code : " +responseCode);
        //Reading Data and
        BufferedReader readin = new BufferedReader(new InputStreamReader(con.getInputStream()));
        String inputLine;
        StringBuffer response = new StringBuffer();
        while ((inputLine = readin.readLine()) != null) {
            response.append(inputLine);
        }
        readin.close();
        //System.out.println(response.toString());
        String jsonresp = new String(response.toString());
        //System.out.println(jsonresp);
        JSONObject myResponse = new JSONObject(jsonresp);
        JSONArray test = myResponse.getJSONArray("targets");
        //System.out.println(test);
        return test;
    }
}

I created the new network class as the error, which was displayed in the textview field was: android.os.NetworkOnMainThreadException. However, this didn’t seem to do the job and the same error is still shown. I have no idea on how to continue from here. When debugging, the debugger always runs until the line which I marked with !!! in the code. Then it jumps to the catch exception in the main activity.

Looking forward to your answers!