Internet data connection fails - http

Question

My users are reporting that when they download a JSON file using WiFi, the app works like charm, but when they attempt to download the same file using their data connection: GPRS, 3G, 3.5G etc... the app force closes. It doesn't happen with all types of smartphones, e.g, with my LG Optimus Black it doesn't happen.
To retrieve this file I use an AsyncTask.
private class GetData extends AsyncTask<Void, Void, Void> {
protected Void doInBackground(Void... args) {
DefaultHttpClient httpclient = new DefaultHttpClient();
try {
HttpGet httpget = new HttpGet("http://url.com);
HttpResponse response = httpclient.execute(httpget);
strPlayers = inputStreamToString(response.getEntity().getContent()).toString();
}
catch (IOException e) { e.printStackTrace(); }
finally { httpclient.getConnectionManager().shutdown(); }
return null;
}
protected void onPostExecute(Void result) {
Players players = new Gson().fromJson(strPlayers, Players.class);
quantity_darkmatter.setText(String.valueOf(players.userName));
}
}
Here's the StackTrace()
java.lang.RuntimeException: Unable to start activity ComponentInfo{carl.fri.fer.omegan/carl.fri.fer.omegan.Research}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1659)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1675)
at android.app.ActivityThread.access$1500(ActivityThread.java:121)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:943)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:130)
at android.app.ActivityThread.main(ActivityThread.java:3701)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:624)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at carl.fri.fer.omegan.Research.onStart(Research.java:613)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1129)
at android.app.Activity.performStart(Activity.java:3791)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1632)
... 11 more
What can be the problem?

Answer 1

For non-WIFI the connection might take considerably more time, so it might be an issue of connection timeout, when that happens strPlayers will be blank and as there is no errorhandling in onPostExecute this might give Gson.fromJson hickups and make it throw an exception... try testing that strPlayers!=null before trying to parse it or putting it in a try-catch block to see if it throws an exception of some sort.
Is there any output of the e.printStackTrace() in the doInBackground function?