The scroll state hoisting for the HomeRoute

HomeRouteScrollState.kt

// Copyright 2022 Google LLC.
// SPDX-License-Identifier: Apache-2.0

@Composable
fun HomeRoute(
    isExpandedScreen: Boolean,
    isArticleOpen: Boolean,
    selectedArticleId: String,
    onSelectArticle: (String) -> Unit,
    onArticleBackPress: () -> Unit,
    // ...
) {
    // Hoist the lazy list states for the list and the details to
    // preserve the scroll through any changes to the content.
    val homeListLazyListState = rememberLazyListState()
    val articleDetailLazyListStates = allArticles.associate { article ->
        key(article.id) {
            article.id to rememberLazyListState()
        }
    }

    // ...
    if (isExpandedScreen) {
        HomeListWithArticleDetailsScreen(
            selectedArticleId = selectedArticleId,
            onSelectArticle = onSelectArticle,
            homeListLazyListState = homeListLazyListState,
            articleDetailLazyListStates = articleDetailLazyListStates,
            // ...
        )
    } else {
        // if we don't have room for both the list and article details,
        // show one of them based on the user's focus
        if (isArticleOpen) {
            ArticleScreen(
                selectedArticleId = selectedArticleId,
                articleDetailLazyListState = articleDetailLazyListStates[selectedArticleId],
                // ...
            )
            BackHandler {
                onArticleBackPress()
            }
        } else {
            HomeListScreen(
                onSelectArticle = onSelectArticle,
                homeListLazyListState = homeListLazyListState,
                // ...
            )
        }
    }
}