SavedStateHandle in Android Kotlin

Introduction

SavedStateHandle helps you save and restore small pieces of data in your app when the screen rotates or the app is temporarily stopped. It keeps your app's state safe without extra work.

You want to keep user input in a form when the phone rotates.

You need to save a counter value during configuration changes.

You want to restore UI state after the app is killed and restarted by the system.

Syntax

Android Kotlin

class MyViewModel(private val state: SavedStateHandle) : ViewModel() {
    fun saveData(key: String, value: String) {
        state.set(key, value)
    }

    fun getData(key: String): String? {
        return state.get<String>(key)
    }
}

SavedStateHandle is usually passed to your ViewModel by the system.

You use set(key, value) to save and get(key) to retrieve data.

Examples

Saves a username and then retrieves it.

Android Kotlin

state.set("username", "Alice")
val name = state.get<String>("username")

Gets a click count or starts at 0, then increases it by 1.

Android Kotlin

val count = state.get<Int>("clickCount") ?: 0
state.set("clickCount", count + 1)

Sample App

This ViewModel saves a count number. It starts at 0 if no saved value exists. When increment is called, it adds 1 and saves it. The count stays even if the screen rotates.

Android Kotlin

class CounterViewModel(private val state: SavedStateHandle) : ViewModel() {
    fun getCount(): Int {
        return state.get<Int>("count") ?: 0
    }

    fun increment() {
        val current = getCount()
        state.set("count", current + 1)
    }
}

// Usage in Activity (requires SavedStateViewModelFactory):
// val factory = SavedStateViewModelFactory(this.application, this)
// val viewModel = ViewModelProvider(this, factory).get(CounterViewModel::class.java)
// println(viewModel.getCount()) // prints 0 initially
// viewModel.increment()
// println(viewModel.getCount()) // prints 1 after increment

Important Notes

SavedStateHandle works well for small, simple data like strings and numbers.

It is not meant for large data or complex objects.

Use it to improve user experience by keeping UI state consistent.

Summary

SavedStateHandle saves small data automatically during configuration changes.

Use set and get methods to store and retrieve data.

It helps keep your app state safe without extra code for saving/restoring.