Mastering Jetpack Compose: Optimizing Recomposition for Better Performance

Unlock the secrets to enhancing your Jetpack Compose applications by minimizing unnecessary recompositions for smoother and faster UI rendering

5 min readAug 5, 2024

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Introduction

What is Jetpack Compose? Jetpack Compose is Android’s modern toolkit for building native UI. It simplifies and accelerates UI development on Android with less code, powerful tools, and intuitive Kotlin APIs.

Why Optimize Recomposition? Optimizing recomposition is crucial for performance. Unnecessary recompositions can lead to sluggish UIs, high CPU usage, and increased battery consumption. By minimizing these, you can ensure a smoother user experience and more efficient apps.

Understanding Recomposition

What is Recomposition? Recomposition is the process of updating the UI in response to state changes. In Jetpack Compose, whenever the state of a composable changes, the framework triggers a recomposition to reflect the new state in the UI.

When Does Recomposition Occur? Recomposition happens when:

A state that a composable function reads changes.
Parameters of a composable function change.
Lambda functions or function references change.

Identifying Unnecessary Recompositions

Tools for Detecting Recompositions Utilize the Android Studio Profiler to monitor recompositions. Debug logs and the Recompose Highlighter can also help identify unnecessary recompositions.

Common Sources of Unnecessary Recompositions

The below examples are very simple and are used just for a demonstration. In our production codebases we have lots of UI elements. So lets keep it simple in this article.

1. Overusing `@Composable` Functions

Problem: Breaking down the UI into too many small composables can lead to excessive recompositions. While it’s good practice to create reusable and modular composable functions, overdoing it can backfire.

Example:

@Composable
fun UserProfile() {
    Column {
        UserAvatar()
        UserName()
        UserBio()
    }
}

@Composable
fun UserAvatar() {
    Image(painter = painterResource(R.drawable.avatar), contentDescription = "User Avatar")
}

@Composable
fun UserName() {
    Text(text = "John Doe")
}

@Composable
fun UserBio() {
    Text(text = "Lorem ipsum dolor sit amet.")
}

In the above example, each part of the user profile is broken down into separate composable functions. While this is good for code organization, it can lead to unnecessary recompositions if not managed properly.

Solution: Group related UI elements together and use remember and rememberUpdatedState to manage recompositions efficiently.

Optimized Example:

@Composable
fun UserProfile() {
    val avatarPainter = remember { painterResource(R.drawable.avatar) }
    val userName = remember { "John Doe" }
    val userBio = remember { "Lorem ipsum dolor sit amet." }
    Column {
        Image(painter = avatarPainter, contentDescription = "User Avatar")
        Text(text = userName)
        Text(text = userBio)
    }
}

By using remember, we ensure that the painterResource, userName, and userBio values are not recomposed unnecessarily.

2. Inefficient State Management

Problem: Misusing state can trigger unwanted recompositions. When state variables are not managed properly, any change to the state can cause recompositions of entire composables that depend on that state, even if only a part of the composable needs to be updated.

Example:

@Composable
fun Counter() {
    var count by remember { mutableStateOf(0) }
    Column {
        Text(text = "Count: $count")
        Button(onClick = { count++ }) {
            Text("Increment")
        }
        // Other UI components that don't need to recompose on count change
    }
}

While the above behavior is usually fine, if you have a more complex UI where unnecessary recompositions might be a concern, you can isolate state-dependent parts to minimize recompositions further.

Solution: Isolate state changes to specific parts of the UI that need to update.

Optimized Example:

@Composable
fun Counter() {
    var count by remember { mutableStateOf(0) }
    Column {
        CountDisplay(count)
        IncrementButton { count++ }
        // Other UI components that don't recompose
    }
}

@Composable
fun CountDisplay(count: Int) {
    Text(text = "Count: $count")
}

@Composable
fun IncrementButton(onClick: () -> Unit) {
    Button(onClick = onClick) {
        Text("Increment")
    }
}

By isolating CountDisplay and IncrementButton, only the necessary composables are recomposed when count changes.

3. Using Mutable States Inappropriately

Problem: Using mutable states incorrectly can lead to unnecessary recompositions. Mutable states should be used judiciously and updated only when necessary.

Example:

@Composable
fun UserProfile() {
    var user by remember { mutableStateOf(User("John Doe", "Lorem ipsum dolor sit amet.")) }
    Column {
        Text(text = user.name)
        Text(text = user.bio)
        Button(onClick = { user = user.copy(name = "Jane Doe") }) {
            Text("Change Name")
        }
    }
}

data class User(val name: String, val bio: String)

In this example, changing the user’s name causes the entire Column to recompose.

Solution: Use immutable states and rememberUpdatedState to manage state changes efficiently.

Optimized Example:

@Composable
fun UserProfile() {
    val userName = remember { mutableStateOf("John Doe") }
    val userBio = remember { "Lorem ipsum dolor sit amet." }
    Column {
        Text(text = userName.value)
        Text(text = userBio)
        Button(onClick = { userName.value = "Jane Doe" }) {
            Text("Change Name")
        }
    }
}

@Composable
fun UserBio(bio: String) {
    Text(text = bio)
}

By separating the user’s name and bio, we ensure that only the Text displaying the user's name recomposes when the name changes.

Conclusion: Achieving Smooth and Efficient UI with Jetpack Compose

Optimizing recomposition in Jetpack Compose is essential for creating performant and responsive applications. By understanding when and why recompositions occur, and by implementing strategies to minimize unnecessary recompositions, you can ensure your apps run smoothly and efficiently. Here are the key takeaways:

Understand Recomposition: Recognize what triggers recompositions and how they impact your app’s performance.
Detect Unnecessary Recompositions: Utilize tools like the Android Studio Profiler, debug logs, and the Recompose Highlighter to identify and diagnose performance bottlenecks.
Optimize @Composable Functions: Balance modularity and performance by grouping related UI elements and using remember to manage state efficiently.
Manage State Effectively: Isolate state changes to specific UI parts and use immutable states and rememberUpdatedState to prevent excessive recompositions.

By mastering these techniques, you can unlock the full potential of Jetpack Compose, delivering a seamless and enjoyable user experience. Continually monitor and refine your composables, and embrace the best practices for state management to create high-performance Android applications.

For further learning, explore the official Jetpack Compose documentation and stay updated with the latest advancements in the Android development ecosystem.

Happy coding!