Handling State Efficiently with Jetpack Compose
As Android developers, managing UI state has always been a critical part of building responsive and dynamic applications. With Jetpack Compose, Google’s modern toolkit for building native Android UIs, we have new tools to manage state in a more declarative and intuitive way. However, it’s still important to handle state efficiently to ensure our apps perform well and remain easy to maintain.
In this post, I’ll walk you through some best practices for handling state efficiently in Jetpack Compose, highlighting common pitfalls and how to avoid them.
Remembering State with remember
One of the core ideas in Compose is that the UI is a function of state. That means every time state changes, the UI is recomposed. To persist state across recompositions, we use remember.
In the example above, remember ensures that the count state survives recompositions. Without remember, the count would reset to 0 every time the composable function is called.
Using rememberSaveable for Persistent State
While remember helps preserve state across recompositions, it does not survive configuration changes (like screen rotations). To handle this, use rememberSaveable, which saves the state to the saved instance state bundle and restores it after configuration changes.
This ensures that the count value persists through rotations and process death without requiring additional logic.
Lifting State (State Hoisting)
A common best practice in Compose is to “lift state” to a higher level, meaning that instead of keeping the state inside a composable, you pass it down as parameters from the parent composable. This helps avoid tightly coupling the state to the UI and makes it easier to test and manage.
And in the parent composable:
Managing Complex State with ViewModel
For more complex scenarios, you’ll want to manage your state in a ViewModel. Jetpack Compose integrates seamlessly with the ViewModel architecture component, which allows you to handle business logic, UI events, and state in a lifecycle-aware way.
In your composable, you can observe this state using collectAsState:
Using ViewModel and StateFlow (or LiveData), you ensure that your state survives process death and is lifecycle-aware, making your app more robust.
Avoiding Unnecessary Recomposition
One of the key performance optimizations in Jetpack Compose is reducing unnecessary recompositions. Unnecessary recompositions can occur when mutable objects or lambdas are passed directly to a composable, leading to performance issues. In this solution, we’ll demonstrate how to handle this efficiently with ViewModel and UiState to avoid redundant recompositions.
- Create the UiState
First, define a UiState to represent the state of your UI:
This UiState holds the state of your counter and potentially other UI-related data (such as a loading indicator, errors, etc).
2. ViewModel to Manage State
Next, create a ViewModel to manage this state. Use MutableStateFlow to hold the state and expose it as a StateFlow to your composables.
3. Composable to Observe the ViewModel
In the composable, you can observe the uiState from the ViewModel using collectAsState. This ensures that the UI only re-renders when necessary.
In this case:
- The lambdas passed to onIncrement and onLoad are stable because they only capture the viewModel instance (which is stable).
- Compose will automatically optimize this and avoid unnecessary recompositions.
Wrap-Up: Emitting Sealed Classes for Better State Management
In addition to handling state efficiently using StateFlow and UiState, you can take your state management to the next level by emitting sealed classes from your ViewModel. This approach allows you to represent complex UI states like loading, success, error, or other specific events in a more structured and readable way.
For example, you can define a sealed class to represent different states of your UI:
And in your ViewModel, you can emit different states based on the business logic:
In your composable, you can handle these different states and show the appropriate UI based on the state:
Benefits of Using Sealed Classes for State Management:
• Clarity: Sealed classes provide clear, well-defined states for your UI, reducing ambiguity.
• Extensibility: As your app grows, you can easily add new states (like error, empty state, etc.) without introducing fragile logic.
• Type Safety: By using sealed classes, you can ensure the compiler will enforce exhaustiveness checks, meaning you’ll handle every possible state in your UI.
By combining Jetpack Compose’s reactive nature with sealed classes, you can achieve more maintainable, scalable, and predictable UI state management in your applications.
Thats it!
If this article helped you understand a little better state management in compose you can leave a 👏, any questions feel free to leave a comment, thanks!
