Hi all. Trying to use interop with a pre-written `...

# compose

[xxfast]

Hi all. Trying to use interop with a pre-written RecyclerView within a @Composable like this

@Composable
fun ComposeRecyclerView(items: Items) {
  
  val adapter: RecyclerView.Adapter by remember { mutableStateOf( RecyclerView.Adapter()) }

  AndroidView(
    modifier = Modifier.fillMaxSize(),
    factory = { context -> RecyclerView(context) },
    update = { recyclerView ->
      if (recyclerView.adapter == null) {
        recyclerView.adapter = adapter
        recyclerView.adapter?.stateRestorationPolicy =
          RecyclerView.Adapter.StateRestorationPolicy.PREVENT_WHEN_EMPTY
      }
  
      adapter.set(animatedState.items)
    }
  )
}

This doesn't seem to work. Is this the right way to use a legacy RecyclerView within Compose? Google is failing me because it keep showing me LazyColumn APIs which is not what I'm trying to achieve here 😅

[czuckie]

this looks correct, except you're not setting a layout manager for the recycler view? (And when I say correct, I mean, this would be how I'd attempt to do such a thing and not that it's actually correct 😂)

[xxfast]

ah crap that was it 😅

[xxfast]

thanks. I forgot how bad recycler APIs really were

[czuckie]

I can't count how many times I've made the exact same mistake, good luck!

[Ben Trengrove [G]]

Does the adapter actually change? I don't think you need it in a mutable state, you could move it to the factory lambda.

[Ben Trengrove [G]]

factory = { context -> RecyclerView(context).apply {
   val myAdapter = RecyclerView.Adapter()
   myAdapter..stateRestorationPolicy =        RecyclerView.Adapter.StateRestorationPolicy.PREVENT_WHEN_EMPTY
   adapter = myAdapter
 }

Something like that

[Ben Trengrove [G]]

It would save that null check in update

[xxfast]

I see, nah the adapter wasn't changing - I just needed a reference to my custom adapter by avoiding a cast of recycler.adapter.

[Ben Trengrove [G]]

One other note, if you just need to remember something to avoid reallocating it, no need for mutableStateOf. You can just do remember { MyObject() }

[xxfast]

Yup you are correct. This took me a while to wrap my head around. If i got this correctly - State<T> (from remember { mutableStateOf() }) helps to trigger recomposition when its state changes. However, remember { YourObject } just prevents reallocation when the @Composable function is executed multiple times

[Ben Trengrove [G]]

They are two distinct concepts.

remember - caches objects across recompostion
mutableStateOf() - creates a new mutable state.

If you didn't remember your mutableStateOf, you would be creating a new mutable state on every recomposition