Hi, i was looking at JetNews source code, Can someone please help me understand the need of key here...

# compose

[Shakil Karim]

Hi, i was looking at JetNews source code, Can someone please help me understand the need of key here, is there any downside if don't use it?
https://github.com/android/compose-samples/blob/84dc6417dfbd6408f498d71afcc1272087[…]ws/app/src/main/java/com/example/jetnews/ui/home/HomeScreens.kt

[jasu]

Its mostly for performance improvement. Basically prevents compose not to recompose on every recomposition. Works as identifier for a particular item to identify it later on time

[Shakil Karim]

Thanks, but doesn't LazyColumn under Key do the same, if state is not changed it will not recompose ?

[jasu]

yes it does, but in given context only thing I can conclude is they want the down tree to recompose when post id changes not otherwise

[Albert Chang]

This has nothing to do with performance. The reason is explained in the comment above, i.e. to recreate a completely new LazyColumn when the post id changes.

[Shakil Karim]

Thanks @Albert Chang When do you think we need a new LazyColumn ? I mean isn't changing the State of LazyColumn will be enough?

[Albert Chang]

Without the key, states of the items in it such as PostTopBar and postContentItems will not change even if the LazyListState changes.

[Shakil Karim]

Ah! Got it Thanks 👍