🚀 Stop Using mutableStateOf for Primitive Types in Android Compose

 Boost your app’s performance and reduce GC pressure by switching to specialized primitive state holders.

Stop Using mutableStateOf for Primitive Types in Android Compose

If you’ve been building with Jetpack Compose, mutableStateOf<T>() is likely your go-to tool for reactivity. But if you’re using it to track a simple Int, Float, or Boolean, you might be accidentally inviting the Garbage Collector to slow down your UI.

With the release of Compose 1.5+, the team introduced specialized state holders for primitives. Here is why you should migrate your code from “generic” to “optimized.”

🧐 The Problem: The “Generic” Tax

When you write mutableStateOf(0), you are using a generic state holder. Because mutableStateOf<T> is generic, the JVM cannot store the raw primitive int. Instead, it uses Auto-Boxing to wrap that integer into an Integer object.

Why does this matter? Every time your state updates (e.g., a counter incrementing), a new wrapper object may be allocated. While the JVM does use an IntegerCache for small values (typically -128 to 127), you cannot rely on this for high-frequency updates like animation offsets or sensor data.

In high-frequency scenarios, this constant “boxing and unboxing” creates Garbage Collection (GC) pressure. If the GC has to kick in frequently to clean up these discarded wrapper objects, you get “jank” — those tiny, annoying stutters in your smooth 120Hz animations.

✅ The Solution: Primitive State Holders

Jetpack Compose now provides specialized functions that store values as raw primitives, bypassing the wrapper class entirely:

  • 💠 mutableIntStateOf(0)
  • 💠 mutableFloatStateOf(0f)
  • 💠 mutableLongStateOf(0L)
  • 💠 mutableDoubleStateOf(0.0)
  • 💠 mutableBooleanStateOf(false) (Stable since Compose 1.6)

These use specialized classes like ParcelableSnapshotMutableIntState under the hood to keep your data "flat" and fast.

💻 Code Comparison: Real-World Example

Let’s look at a High-Frequency Timer. In this scenario, the state changes every few milliseconds.

The “Generic” Way (Object Overhead)

// Every update here risks a new 'Float' object allocation
var progress by remember { mutableStateOf(0f) } 

// High-frequency update loop
LaunchedEffect(Unit) {
    while(true) {
        withFrameMillis { progress += 0.01f }
    }
}

The “Optimized” Way (Zero Allocation)

// Internally uses a raw primitive 'float'
// No boxing, no extra objects, maximum performance
var progress by remember { mutableFloatStateOf(0f) }

// The developer API remains identical!
LinearProgressIndicator(progress = progress)

⚠️ The Catch: The Nullability Trade-off

The only “downside” to these specialized holders is that they cannot be null. A mutableIntStateOf is a raw int, and a raw int cannot be null.

What if you need a null state?

  • Use a Sentinel Value: Use -1 or Float.NaN to represent an empty state.
  • Fallback to Generic: If null is a core part of your business logic (e.g., mutableStateOf<Int?>(null)), stay with the generic version. The performance cost is worth the type safety in that specific case.

💡 The Verdict: Optimization as a Habit

Will you see a 50% speed boost in a simple login form? No. However, in Animations, Scroll Listeners, and Custom Drawings, these small wins add up.

By using mutableIntStateOf, you are writing "Senior-level" Compose code: code that isn't just functional, but is aware of the underlying JVM and memory efficiency.

🙋‍♂️ Frequently Asked Questions (FAQs)

Does this apply to StateFlow?

No. StateFlow<T> is inherently generic, so primitives used in Flows will always be boxed. This optimization is specific to the Compose Snapshot State system.

Is it okay to use these in my ViewModel?

Yes! You should use them in ViewModels just like you would use mutableStateOf. It keeps your state exposure efficient from the data layer to the UI.

What version of Compose do I need?

These were introduced in Compose 1.5.0. mutableBooleanStateOf became stable in 1.6.0. If you are on an older version, it's time for an update!

💬 Let’s Discuss!

  • Do you use sentinel values (like -1) for “empty” states, or do you prefer nullable generics?
  • Have you ever encountered “GC Jank” in a complex Compose animation?
  • Which primitive state do you find yourself using most often?

Drop a comment below! If you found this helpful, give it a 👏 and share it with your fellow Android devs!

📘 Master Your Next Technical Interview

Since Java is the foundation of Android development, mastering DSA is essential. I highly recommend “Mastering Data Structures & Algorithms in Java”. It’s a focused roadmap covering 100+ coding challenges to help you ace your technical rounds.

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