Hi how to create expand list

[nandu_aeer (Nandu)]

Wow great…

[varsha (Extension Developer ⚘)]

Thanks …

[josep_maria_pons_morey]

I have tried searching the forum but have not found an answer.
I am using the expandable listview but there are a bug with the child_title list.
The firs example works fine, but the second example dont work, the apk stops, its seem the “join” can’t be used on this extension. Its correct?, any idea? its possible to correct it? thanks and sorry for anything, this is my first post.

this dont work