remember and mutableStateOf in Android Kotlin

Introduction

We use remember and mutableStateOf to keep track of values that can change in our app's screen. This helps the app update the screen when something changes.

When you want to save a user's input in a text box and show it on the screen.

When you want to toggle a button's color when it is clicked.

When you want to count how many times a button is pressed and show the count.

When you want to remember if a checkbox is checked or not.

Syntax

Android Kotlin

val variableName = remember { mutableStateOf(initialValue) }

remember keeps the value during recompositions (screen redraws).

mutableStateOf creates a value that can change and notify the screen to update.

Examples

This creates a number count starting at 0 that can change and update the screen.

Android Kotlin

val count = remember { mutableStateOf(0) }

This creates a text name starting empty that can change when the user types.

Android Kotlin

val name = remember { mutableStateOf("") }

This creates a true/false value isChecked starting as false.

Android Kotlin

val isChecked = remember { mutableStateOf(false) }

Sample App

This app shows a number that starts at 0. When you press the button, the number goes up by 1. The screen updates automatically because we use remember and mutableStateOf.

Android Kotlin

import androidx.compose.material3.*
import androidx.compose.runtime.*
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.foundation.layout.*
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp

@Composable
fun CounterApp() {
  val count = remember { mutableStateOf(0) }

  Column(modifier = Modifier.padding(16.dp)) {
    Text(text = "You clicked: ${count.value} times")
    Spacer(modifier = Modifier.height(8.dp))
    Button(onClick = { count.value += 1 }) {
      Text("Click me")
    }
  }
}

@Preview
@Composable
fun PreviewCounterApp() {
  CounterApp()
}

Important Notes

Always use remember with mutableStateOf inside a @Composable function to keep state across recompositions.

Change the value by updating variable.value, not by reassigning the whole variable.

Using these helps your app respond to user actions smoothly.

Summary

remember keeps values during screen redraws.

mutableStateOf creates a value that can change and update the UI.

Use them together to make interactive and dynamic screens.