ListWithMultipleItemTypes.kt — Incorrect usage of items() lambda and contentType

[hijamoya]

The code snippet in ListWithMultipleItemTypes.kt (used in the Build a list with multiple item types Quick Guide) contains multiple logical errors.

Current Code

@Composable
fun ListWithMultipleItems(messages: List<Any>) {
    LazyColumn {
        items(
            messages.size,
            contentType = { it }
        ) {
            for (message in messages)
                when (message) {
                    is MediaStore.Audio -> AudioMessage(message)
                    is Text -> TextMessage(message)
                }
        }
    }
}

Issues
contentType = { it } returns the index (Int), not the content type. The it parameter inside the contentType lambda is the item index. This means every item gets a different content type (0, 1, 2, …), which completely defeats the purpose of contentType — Compose cannot reuse compositions across items of the same type. It should be something like { messages[it]::class }.

The items content lambda iterates the entire list for every single item. The lambda parameter it is the index of the current item, but instead of using messages[it] to render only the current item, the code uses for (message in messages) which iterates over all messages for each row. For a list of N items, this produces N × N composables instead of N.

This is confusing for developers trying to learn from the snippet.