Jetpack Compose remember — Complete Guide

In this tutorial, you'll learn about Jetpack Compose remember. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

The Problem

Your remember block recomputes on every recomposition despite the key, or the value is shared across instances when it shouldn't be.

Wrong Approach ❌

@Composable
fun BadRemember(counter: Int) {
    // No key — recomputes when counter changes, not when it should
    val result = remember {
        computeExpensive(counter) // Computed once on first composition only
    }

    // Actually want to recompute when counter changes
    val shouldRecompute = remember(counter) {
        computeExpensive(counter) // OK, but captured differently
    }
}

// State shared accidentally across instances
object SharedState {
    var count by mutableStateOf(0) // Global!
}

Output: Stale computed values or unexpected state sharing.

Right Approach ✅

@Composable
fun GoodRemember(input: String) {
    // Recomputes only when input changes
    val processed = remember(input) {
        input.lowercase().trim()
    }

    // Stored value survives recomposition
    var expanded by remember { mutableStateOf(false) }

    // Derived computation that updates reactively
    val derived by remember(input) {
        derivedStateOf { input.length }
    }

    // Expensive computation cached
    val expensive by remember(input) {
        mutableStateOf(computeExpensive(input))
    }
}

@Composable
fun InstanceScopedState() {
    // Scoped to this composition position — not shared
    val localState = remember { mutableStateOf(0) }
}

Output: Correct scoping with memoization and reactive updates.

Prevention

• Always provide key parameters to remember when the value depends on them.
• Use derivedStateOf for computed values to avoid redundant recompositions.
• Scope state to the nearest common composable ancestor, not a global.
• Use rememberSaveable for state that must survive Process death.

Common Mistakes with compose remember

1. Mixing let bindings with <- bindings in do notation, producing type errors
2. Overlapping type class instances that cause GHC to reject the program with ambiguous dispatch errors
3. Non-exhaustive pattern matches that compile with warnings then crash at runtime

These mistakes appear frequently in real-world Android code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ