🔄 Understanding Recomposition in Jetpack Compose

Everything you need to know to master reactive UI updates

Jetpack Compose introduces a radically different way of building UI in Android. Unlike the imperative approach in XML-based UI development, Compose is declarative and reactive. One of its most powerful — yet sometimes misunderstood — concepts is Recomposition.

In this blog, we’ll break down:

• What recomposition is

• When it happens

• How to control it

• Common pitfalls

• Best practices to avoid unnecessary recompositions

🧠 What is Recomposition?

Recomposition is the process where Jetpack Compose re-runs composable functions to update the UI when state changes.

📘 Think of it as: Compose saying, “Hey, something changed — let me redraw the UI with the new data.”

It doesn't redraw the entire screen. Instead, it intelligently re-invokes only the affected parts of your UI tree, thanks to its fine-grained UI diffing engine.

📍 When Does Recomposition Happen?

Recomposition is triggered when:

1. A State or MutableState object changes.

2. A remember or derivedStateOf value changes.

3. A LaunchedEffect gets a new key.

4. A ViewModel emits new values via LiveData/Flow/StateFlow.

5. Side-effect APIs (e.g., , ) get recomposed.

Here’s a quick example:

Every time the button is clicked, triggers a recomposition, updating the text.

🔍 How Does Compose Decide What to Recompose?

Jetpack Compose uses smart invalidation tracking. It:

• Keeps track of the values read inside a composable.

• Re-runs only the affected composables when those values change.

So, if a child composable doesn’t use a changed state, it won’t recompose — optimizing performance.

🚨 Common Recomposition Pitfalls

❌ 1. Unnecessary recomposition due to state hoisting gone wrong:

If changes frequently but doesn't affect , you're still recomposing it. Solution? Lift state only when necessary or consider using .

❌ 2. Using remember incorrectly:

Use to memoize values between recompositions.

❌ 3. Forgetting remember in lambdas:

Without , the lambda can be recreated on every recomposition, possibly triggering unnecessary re-renders of children.

✅ Best Practices to Control Recomposition

🟢 Use remember + mutableStateOf

To hold and observe reactive state changes.

🟢 Use rememberUpdatedState

To keep latest lambdas across recompositions, especially inside .

🟢 Use derivedStateOf

For computed state that depends on other states.

🟢 Use key() to isolate recompositions

🧪 Debugging Recomposition

Use the following tools:

• inside composables

• (in Dev options)

• Android Studio’s Layout Inspector in Compose mode

• with recomposition tracing

🚀 Final Thoughts

Recomposition is at the heart of what makes Jetpack Compose reactive, efficient, and powerful. Understanding how and when it happens lets you:

• Write more performance-optimized UIs

• Avoid unnecessary re-renders

• Improve app responsiveness and battery usage

Remember, state drives UI in Compose. If you understand recomposition, you understand Compose.

✍️ Author: Rahul Pahuja 📍 Staff Mobile Engineer | Android, iOS, Flutter | CyberArk| Coforge | Ex-Conviva 🔗 LinkedIn