Showing Error :Attempt to invoke interface method 'int java.util.List.size()' on a null object reference

Question

I\'m creating an app that display contact list in a listview.The problem is I\'m getting the following error when I run my app and I\'m struggling to fix it:

Answer 1

Extract this line

List<ContactModel> contactModelList = new ArrayList<>();

before the try block and instead of return null; use return contactModelList;

Looks like your parsing fails and you pass a null object to onPostExecute().

Answer 2

The List object which you passed into the adapter is null. So when the adapter calls list.Size(), a null pointer exception is thrown.

Use a debugger, set a breakpoint somewhere around com.kksworld.jsonparsing.MainActivity$JSONTask.onPostExecute(MainActivity.java:48), and work your way backward from there if you can't figure it out.

One assumes that your json parse failed somehow or another.

Answer 3

I was building similar app from youtube video and I've got same error, but I saw also error "Cleartext HTTP traffic not allowed to site.com", so I found solution android:usesCleartextTraffic="true" here Android 8: Cleartext HTTP traffic not permitted and it solved all problems without modifying MainActivity. Btw, on API 16 it wasn't showing errors.