Need to add import androidx.core.view.children

Downloaded a demo to check something inside it these imports works

import androidx.core.view.children
import androidx.core.animation.doOnEnd
import androidx.core.animation.doOnStart

but i can't use inside my project , it gives me error with children and animation

Unresolved reference: animation

BTW i added AndroidX from this

https://stackoverflow.com/a/58134686/8669531

if this will make a difference