Enabling Jetpack Compose for Library Modules in Gradle

Jetpack Compose is revolutionizing Android UI development with its declarative approach, allowing developers to create intuitive, performant, and modern UIs with less boilerplate code. While integrating Compose in application modules is relatively straightforward, enabling Compose in library modules introduces unique considerations and best practices.

In this blog post, we'll dive deep into the steps required to enable Jetpack Compose for library modules in Gradle, explore common challenges, and discuss advanced tips for optimizing your library's build and usage.

Prerequisites

Before you start integrating Jetpack Compose into your library module, ensure the following:

  • Android Studio: Use a recent version, ideally Arctic Fox (2020.3.1) or newer, as Compose support requires an updated IDE.

  • Compose Version: Use a stable or compatible version of Jetpack Compose.

  • Gradle: Minimum required version is 7.0.0.

  • Kotlin: Ensure you're using Kotlin 1.5.21 or newer.

Step-by-Step Guide

1. Enable Jetpack Compose in the Library Module

To use Jetpack Compose in a library module, you need to enable Compose-specific configurations in the build.gradle (or build.gradle.kts) file.

Add Compose Dependencies

Add the required dependencies for Jetpack Compose in your library module's build.gradle file:

def compose_version = '1.5.1' // Use the latest compatible version

android {
    compileSdk = 34 // Ensure this matches your app's compileSdk

    defaultConfig {
        minSdk = 21 // Jetpack Compose requires a minimum of API 21
    }

    buildFeatures {
        compose true
    }

    composeOptions {
        kotlinCompilerExtensionVersion = compose_version
    }

    kotlinOptions {
        jvmTarget = '1.8'
    }
}

dependencies {
    implementation "androidx.compose.ui:ui:\$compose_version"
    implementation "androidx.compose.material:material:\$compose_version"
    implementation "androidx.compose.ui:ui-tooling-preview:\$compose_version"
    debugImplementation "androidx.compose.ui:ui-tooling:\$compose_version"
}

Update gradle.properties

Ensure gradle.properties includes Compose-specific flags:

org.gradle.jvmargs=-Xmx2048m
android.enableJetifier=true
android.useAndroidX=true
kotlin.compiler.extension.version=1.5.1

2. Export Compose APIs from Your Library

A library module might expose Compose APIs or UI components for reuse. To allow seamless integration, ensure that the public APIs are well-defined and follow Compose's guidelines for recomposable functions.

Example: Exposing a Compose Component

Define a composable function in your library module:

package com.example.mylibrary

import androidx.compose.runtime.Composable
import androidx.compose.material.Text

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

Developers consuming your library can now use this Greeting composable directly.

Challenges and Solutions

1. Version Conflicts

Jetpack Compose relies on specific versions of Kotlin and Android Gradle Plugin. When enabling Compose in library modules, version conflicts can occur if the consuming app uses different versions.

Solution:

Use api dependencies to ensure consistent versions of Compose libraries are propagated to consuming modules. For example:

dependencies {
    api "androidx.compose.ui:ui:\$compose_version"
    api "androidx.compose.material:material:\$compose_version"
}

Additionally, document the required Compose and Kotlin versions in your library's README to guide consumers.

2. Binary Compatibility

Compose's compiler plugin introduces changes that may affect binary compatibility across library updates.

Solution:

  • Avoid exposing internal Compose implementations (e.g., Modifier chains) in public APIs.

  • Rigorously test your library with each Compose update.

  • Follow Compose API guidelines to ensure stability.

3. Tooling and Preview Support

Developers consuming your library might face issues with the Compose preview feature if dependencies are misconfigured.

Solution:

Include ui-tooling and ui-tooling-preview dependencies in your library:

debugImplementation "androidx.compose.ui:ui-tooling:\$compose_version"
implementation "androidx.compose.ui:ui-tooling-preview:\$compose_version"

Best Practices

1. Modularize Strategically

When using Compose in a library module, ensure clear boundaries between UI-specific code and other logic. For instance, separate Compose-based UI components into a dedicated module to minimize dependencies in non-UI libraries.

2. Optimize Build Times

Compose libraries can increase build times due to the compiler plugin. Use these strategies to mitigate:

  • Enable incremental compilation in gradle.properties:

    kotlin.incremental=true

  • Use lazy dependency resolution by defining dependencies only when needed.

3. Document Compose API Usage

Provide thorough documentation for your library's Compose APIs, including:

  • Required setup steps

  • Minimum supported Compose version

  • Examples of usage in consuming projects

Advanced Use Cases

1. Theme and Styling for Library Components

To ensure consistent theming across consuming apps, provide customizable themes or rely on the app's existing theme. For example:

@Composable
fun LibraryButton(
    text: String,
    onClick: () -> Unit,
    modifier: Modifier = Modifier
) {
    Button(
        onClick = onClick,
        modifier = modifier
    ) {
        Text(text = text)
    }
}

2. Compose Multiplatform Libraries

Jetpack Compose's multiplatform support (Compose for Desktop, Compose for Web) allows libraries to target multiple platforms. Configure your build.gradle for Kotlin Multiplatform if needed:

kotlin {
    android()
    jvm() // For desktop

    sourceSets {
        val commonMain by getting {
            dependencies {
                implementation("org.jetbrains.compose.runtime:runtime:1.5.1")
            }
        }
    }
}

Conclusion

Enabling Jetpack Compose in library modules unlocks a powerful way to create reusable UI components for Android apps. By following best practices and addressing common challenges, you can build robust, user-friendly libraries that leverage the full potential of Compose.

Whether you're crafting UI libraries or integrating Compose into existing ones, the strategies outlined here will ensure a smooth development experience and a high-quality product. Start enabling Jetpack Compose in your library modules today, and share the power of modern UI development!