Jetpack Compose Best Practices

Jetpack Compose, Android's modern toolkit for building native UI, has revolutionized how we create user interfaces. Its declarative nature and powerful features allow for more efficient and enjoyable development. To truly leverage its potential, adhering to best practices is crucial. This post explores some key recommendations for building robust and maintainable Compose UIs.

1. Embrace Declarative Principles

The core of Compose is its declarative paradigm. Instead of imperatively manipulating UI elements, you describe what your UI should look like based on your current state. This means your Composable functions should be:

Pure: Given the same inputs, they should always produce the same output.
Side-effect free: Avoid direct state mutation or network calls within the Composable itself.
Composable: Break down your UI into small, reusable, and focused Composable functions.

A good example of a simple, declarative Composable:

import androidx.compose.material3.Text
import androidx.compose.runtime.Composable

@Composable
fun Greeting(name: String) {
    Text(text = "Hello, $name!")
}
            

2. Manage State Effectively

State management is fundamental. Compose provides several ways to handle state, and choosing the right one is key. For simple UI state that lives only as long as the Composable is on screen, use remember { mutableStateOf(...) }.

import androidx.compose.foundation.layout.Column
import androidx.compose.material3.Button
import androidx.compose.material3.Text
import androidx.compose.runtime.*

@Composable
fun Counter() {
    var count by remember { mutableStateOf(0) }

    Column {
        Text(text = "Count: $count")
        Button(onClick = { count++ }) {
            Text("Increment")
        }
    }
}
            

For state that needs to be shared across multiple Composables or persist beyond the Composable's lifecycle, consider state holders like ViewModel with StateFlow or LiveData.

3. Understand Recomposition

Compose intelligently recomposes only the parts of your UI that have changed. This is a performance benefit, but understanding how it works prevents common pitfalls:

Avoid unnecessary calculations: Complex computations within a Composable that don't depend on state will be re-executed on every recomposition. Memoize expensive operations using remember.
Stable types: Ensure your data classes are @Immutable or @Stable to help Compose optimize recompositions.

4. Optimize Layouts

Compose's layout system is flexible. Use modifiers extensively for layout behavior. For performance, be mindful of nested layouts that can lead to multiple measurement and placement passes.

Use weight() for proportional sizing in Row and Column.
Consider ConstraintLayout for complex, one-pass layouts.
Avoid placing Composables that don't need to be visible or interactive within the layout hierarchy if they are expensive to render.

5. Composition vs. Layout

It's important to distinguish between composition and layout. Composition is the process of calling Composable functions to describe the UI. Layout is the process of measuring and placing these Composables on the screen. Prefer to keep your Composables focused on description rather than complex layout logic.

6. Use Modifiers Wisely

Modifiers are the workhorses of Compose UI. They chain together to add behavior, appearance, and layout aspects to Composables. Apply modifiers in the correct order. For example, padding should typically be applied after size modifiers.

import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.size
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.dp

@Composable
fun StyledBox(text: String) {
    Box(
        modifier = Modifier
            .padding(16.dp) // Padding applied first
            .size(100.dp) // Then size
            .background(Color.Cyan) // Then background
            .padding(8.dp) // Inner padding
    ) {
        Text(text = text)
    }
}
            

7. Keep Composables Small and Reusable

Break down your UI into the smallest possible Composable functions that represent a single logical unit. This improves readability, testability, and reusability.

8. Handle Side Effects Correctly

Effects like launching coroutines, showing dialogs, or navigating should be done using side-effect APIs like LaunchedEffect, SideEffect, produceState, or rememberCoroutineScope.

import androidx.compose.runtime.*
import kotlinx.coroutines.delay

@Composable
fun ShowMessageAfterDelay(message: String) {
    var visible by remember { mutableStateOf(false) }

    LaunchedEffect(Unit) {
        delay(1000)
        visible = true
    }

    if (visible) {
        Text(message)
    }
}
            

Conclusion

Adopting these Jetpack Compose best practices will lead to more robust, performant, and maintainable Android applications. Remember to experiment, read the official documentation, and leverage the vibrant Compose community for continuous learning.

Happy coding!