Jetpack Compose Layout Optimization Best Practices

The author shares practical experience in Jetpack Compose layout optimization based on nearly a year of project development. The article covers six key optimization techniques:

1. Using remember to Reduce Computation When sorting a list in Compose, the sorting operation executes on every recomposition. Using remember with a key caches the sorted result and only recalculates when the source data changes:

val sortList = remember(key1 = list) {
    list.sortedBy { it.age }
}

2. Using key in Lazy Layouts Without a key parameter, adding items to a LazyColumn causes all subsequent visible items to recompose unnecessarily. Adding a unique key ensures only the new item recomposes:

itemsIndexed(list, key = { _, item -> item.id }) { _, item ->
    ClientItem(item)
}

3. Using derivedStateOf to Limit Recomposition When observing frequently changing state like scroll position, use derivedStateOf to prevent unnecessary recompositions. This ensures the button only recomposes when the condition actually changes from false to true, not on every scroll event.

4. Delayed Reading / Skipping Phases Compose has three phases: Composition, Layout, and Drawing. For operations that only affect drawing (like background color changes), use drawBehind to skip composition and layout phases. For state that is read in one scope but used in another, pass a lambda to delay reading until actually needed.

5. Avoiding Backward Writes Never write to state after it has been read in the same composition scope. This causes infinite recomposition loops where the state keeps being modified every frame.

6. Release Mode & R8 Optimization Release mode with R8 and Profile configuration provides the best cold start performance. The Compose baseline profile pre-compiles critical code during app installation via ART (Android Runtime).

The key principle throughout is to minimize unnecessary recompositions to maintain smooth UI performance.