LazyRow for horizontal lists in Android Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What will this LazyRow display?

Consider this Kotlin Compose code snippet using LazyRow. What will the user see on the screen?

Android Kotlin

LazyRow {
  items(3) { index ->
    Text(text = "Item $index")
  }
}

A A horizontal list showing: Item 0, Item 1, Item 2

B An empty screen with no items

C A horizontal list showing only one item: Item 3

D A vertical list showing: Item 0, Item 1, Item 2

💡 Hint

LazyRow arranges items horizontally, and items(3) creates 3 items indexed 0 to 2.

LazyRow creates a horizontal scrolling list. The items(3) block creates 3 items with indices 0, 1, and 2. Each item shows text "Item" plus its index.

📝 Syntax

intermediate

Which option correctly adds padding between items in LazyRow?

You want to add 8.dp horizontal space between each item in a LazyRow. Which code snippet does this correctly?

A LazyRow(spacing = 8.dp) { items(5) { Text("Item") } }

B LazyRow(padding = PaddingValues(horizontal = 8.dp)) { items(5) { Text("Item") } }

C LazyRow(horizontalPadding = 8.dp) { items(5) { Text("Item") } }

D LazyRow(horizontalArrangement = Arrangement.spacedBy(8.dp)) { items(5) { Text("Item") } }

💡 Hint

Use horizontalArrangement with spacedBy to add space between items.

The horizontalArrangement parameter with Arrangement.spacedBy(8.dp) adds 8.dp space between each item horizontally. Other options are invalid parameters.

❓ lifecycle

advanced

What happens if you scroll a LazyRow with many items?

You have a LazyRow with 1000 items. What is the behavior regarding item creation and memory?

A All 1000 items are composed and kept in memory at once, causing high memory use.

B Only visible items are composed and kept in memory; off-screen items are disposed to save memory.

C LazyRow loads items in batches of 100 and discards others immediately.

D LazyRow duplicates items to fill the screen even if fewer items exist.

💡 Hint

LazyRow is designed to be efficient with large lists by composing only visible items.

LazyRow composes only the items visible on screen plus a small buffer. This optimizes memory and performance for large lists.

❓ navigation

advanced

How to detect which item is visible in LazyRow during scroll?

You want to know the index of the first visible item in a LazyRow while the user scrolls. Which approach is correct?

A Use rememberLazyListState() and check state.firstVisibleItemIndex inside LaunchedEffect.

B Use Modifier.onGloballyPositioned to get item positions and calculate visible index manually.

C Use a ScrollListener on LazyRow to get scroll offset and guess visible item.

D LazyRow does not support detecting visible items during scroll.

💡 Hint

LazyListState provides info about visible items and scroll position.

rememberLazyListState() holds the scroll state of LazyRow. Its firstVisibleItemIndex property gives the index of the first visible item, which can be observed in LaunchedEffect or snapshotFlow.

🔧 Debug

expert

Why does this LazyRow not scroll horizontally?

This LazyRow code does not scroll horizontally as expected. What is the cause?

Android Kotlin

LazyRow(modifier = Modifier.fillMaxWidth()) {
  items(5) { index ->
    Text(text = "Item $index", modifier = Modifier.fillMaxWidth())
  }
}

A items(5) is too few items to enable scrolling.

B LazyRow requires a fixed height modifier to enable scrolling.

C Each item uses fillMaxWidth(), so items take full width and block horizontal scrolling.

D LazyRow needs horizontalScroll modifier to scroll.

💡 Hint

Check the width modifiers on items inside LazyRow.

Using Modifier.fillMaxWidth() inside each item makes each item as wide as the LazyRow itself, so items stack vertically and no horizontal scrolling occurs. Items should have fixed or wrap content width.