How to Use remember in Compose in Android: Simple Guide

In Jetpack Compose, use remember to store a value across recompositions so it doesn't reset every time the UI updates. It keeps the state in memory as long as the composable is in the composition, helping you preserve user input or other data easily.

Syntax

The remember function takes a calculation block and returns a stored value that survives recompositions of the composable. It looks like this:

• remember { calculation }: Stores the result of calculation.
• The stored value resets if the composable leaves and re-enters the composition.

kotlin

val myValue = remember { mutableStateOf(0) }

Example

This example shows a button that increments a counter. The counter value is stored using remember, so it keeps its value when the UI updates.

kotlin

import androidx.compose.material3.*
import androidx.compose.runtime.*
import androidx.compose.ui.window.singleWindowApplication

fun main() = singleWindowApplication {
    var count by remember { mutableStateOf(0) }
    Button(onClick = { count++ }) {
        Text("Clicked $count times")
    }
}

Output

A button labeled 'Clicked 0 times' that increments the number each time it is clicked.

Common Pitfalls

Common mistakes when using remember include:

• Using remember outside a composable function, which causes errors.
• Expecting remember to persist data across app restarts; it only lasts while the composable is in memory.
• Not using mutableStateOf inside remember when you want the UI to update on value changes.

kotlin

/* Wrong: remember used outside composable */
@Composable
fun WrongCounter() {
    val count = remember { mutableStateOf(0) } // Correct usage inside composable
}

/* Right: inside composable with delegated property */
@Composable
fun Counter() {
    var count by remember { mutableStateOf(0) }
}

Quick Reference

Remember these tips when using remember:

• Use inside composable functions only.
• Wrap mutable state with mutableStateOf for UI updates.
• Values reset if composable leaves composition.
• Use rememberSaveable to survive process death.

Key Takeaways

remember stores values across recompositions within a composable.

Always use remember inside composable functions to avoid errors.

Combine remember with mutableStateOf to update UI on state changes.

remember does not persist data beyond the composable lifecycle; use rememberSaveable for longer persistence.

Avoid using remember outside composables or expecting it to survive app restarts.