Getting a JSONException: end of input at character 0

You are probably getting a blank response. Its not null but the response is empty. So you are getting this error and not a Nullpointer exception

Check if you are asking for permissions to use the Internet.

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

in the Android Manifest

Check out others at Permissions overview @ https://developer.android.com.