Essential Libraries for Compose Multiplatform App Development

Jetpack Compose has revolutionized Android UI development, and its extension to Kotlin Multiplatform (KMP) allows developers to build cross-platform applications with a single codebase. Leveraging specific libraries in Compose Multiplatform significantly enhances the efficiency and functionality of these applications. This post delves into essential Compose Multiplatform app libraries, providing detailed code examples and insights.

What is Compose Multiplatform?

Compose Multiplatform is a declarative UI framework that enables developers to build applications for Android, iOS, desktop, and web using Kotlin. It utilizes the same principles as Jetpack Compose, emphasizing composable functions and reactive state management.

Why Use Libraries in Compose Multiplatform?

• Code Reusability: Share UI and business logic across platforms.
• Efficiency: Accelerate development by leveraging pre-built components and functionalities.
• Consistency: Ensure a consistent look and feel across different platforms.
• Maintainability: Simplify updates and maintenance with a unified codebase.

Key Compose Multiplatform App Libraries

Several libraries are crucial for building robust Compose Multiplatform applications. Here’s a detailed look at some of the most important ones.

1. Compose UI Libraries

The foundation of any Compose Multiplatform project lies in its UI libraries. These include:

• org.jetbrains.compose.ui:ui-core: Core UI components for building layouts.
• org.jetbrains.compose.ui:ui-tooling: Tools for previewing and debugging UI.
• org.jetbrains.compose.material:material: Material Design components.
• org.jetbrains.compose.foundation:foundation: Fundamental building blocks for UI.

Example of a simple composable:

import androidx.compose.material.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.tooling.preview.Preview

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

@Preview
@Composable
fun PreviewGreeting() {
    Greeting("Compose Multiplatform")
}

2. Kotlin Coroutines

Kotlin Coroutines are essential for handling asynchronous operations such as network requests or database queries. In Compose Multiplatform, they help keep the UI responsive.

Adding Dependencies:

dependencies {
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.3")
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3") // For Android
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-swing:1.7.3")   // For Desktop
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.7.3")    // For Testing
}

Example Using Coroutines:

import kotlinx.coroutines.*
import androidx.compose.runtime.*
import androidx.compose.material.Button
import androidx.compose.material.Text

@Composable
fun CoroutineExample() {
    var result by remember { mutableStateOf("Click the button") }

    val scope = rememberCoroutineScope()

    Button(onClick = {
        scope.launch {
            result = fetchData() // Simulate network request
        }
    }) {
        Text("Fetch Data")
    }
    Text(result)
}

suspend fun fetchData(): String {
    delay(2000) // Simulate network delay
    return "Data fetched!"
}

3. Ktor Client

Ktor Client is a multiplatform HTTP client that simplifies making network requests in Compose Multiplatform. It supports various platforms and provides a clean and efficient API.

Adding Dependencies:

dependencies {
    implementation("io.ktor:ktor-client-core:2.3.9")
    implementation("io.ktor:ktor-client-cio:2.3.9")           // Common engine
    implementation("io.ktor:ktor-client-android:2.3.9")      // Android engine
    implementation("io.ktor:ktor-client-js:2.3.9")           // JavaScript engine
    implementation("io.ktor:ktor-client-iossimulator:2.3.9") // iOS simulator engine
    implementation("io.ktor:ktor-serialization-kotlinx-json:2.3.9")
}

Example Using Ktor Client:

import io.ktor.client.*
import io.ktor.client.engine.cio.*
import io.ktor.client.request.*
import io.ktor.client.statement.*
import kotlinx.coroutines.*
import androidx.compose.runtime.*
import androidx.compose.material.Button
import androidx.compose.material.Text

@Composable
fun KtorExample() {
    var result by remember { mutableStateOf("Click to fetch data") }
    val client = HttpClient(CIO)
    val scope = rememberCoroutineScope()

    Button(onClick = {
        scope.launch {
            try {
                val response: HttpResponse = client.get("https://ktor.io/")
                result = "Response: ${response.status.value}"
            } catch (e: Exception) {
                result = "Error: ${e.message}"
            } finally {
                client.close()
            }
        }
    }) {
        Text("Fetch Data from Ktor")
    }
    Text(result)
}

4. SQLDelight

SQLDelight is a Kotlin library that generates typesafe Kotlin APIs from SQL schemas. It is ideal for managing local data storage across platforms.

Adding Dependencies:

plugins {
    id("app.cash.sqldelight") version "2.0.1"
}

dependencies {
    implementation("app.cash.sqldelight:runtime:2.0.1")
    implementation("app.cash.sqldelight:android-driver:2.0.1")      // Android driver
    implementation("app.cash.sqldelight:sqlite-driver:2.0.1")       // JVM driver
    implementation("app.cash.sqldelight:native-driver:2.0.1")        // Native driver
    implementation("app.cash.sqldelight:coroutines-extensions:2.0.1") // Kotlin coroutines extension
}

Example SQLDelight Usage:

First, define your SQL schema (.sq file):

CREATE TABLE User (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  username TEXT NOT NULL,
  email TEXT NOT NULL
);

insertUser:
INSERT INTO User (username, email) VALUES (?, ?);

selectAllUsers:
SELECT * FROM User;

Then, use it in your Kotlin code:

import com.example.Database
import com.squareup.sqldelight.db.SqlDriver

class DatabaseHelper(driver: SqlDriver) {
    private val database = Database(driver)
    private val dbQueries = database.userQueries

    fun insertUser(username: String, email: String) {
        dbQueries.insertUser(username, email)
    }

    fun getAllUsers(): List {
        return dbQueries.selectAllUsers().executeAsList()
    }
}

// Usage Example:
fun main() {
    // Note: Replace SqlDriver implementation based on the platform.
    // e.g., AndroidSqliteDriver, JdbcSqliteDriver for JVM, etc.
    //val driver: SqlDriver = JdbcSqliteDriver(JdbcSqliteDriver.IN_MEMORY) //example
    //val dbHelper = DatabaseHelper(driver)
    //dbHelper.insertUser("john_doe", "john.doe@example.com")
    //val users = dbHelper.getAllUsers()
    //println(users)
}

5. Settings

Settings is a multiplatform library for storing key-value data persistently. It’s great for saving user preferences and app settings.

Adding Dependencies:

dependencies {
    implementation("com.russhwolf:multiplatform-settings-no-arg:1.1.1")
    implementation("com.russhwolf:multiplatform-settings-coroutines:1.1.1")
    implementation("com.russhwolf:multiplatform-settings-serialization:1.1.1")
}

Example Using Settings:

import com.russhwolf.settings.*

val settings: Settings = Settings() // or Settings(factory.create("my_settings"))

fun saveSetting(key: String, value: String) {
    settings.putString(key, value)
}

fun getSetting(key: String, defaultValue: String): String {
    return settings.getString(key, defaultValue)
}

// Usage Example:
fun main() {
    saveSetting("theme", "dark")
    val currentTheme = getSetting("theme", "light")
    println("Current theme: $currentTheme")
}

6. ViewModel and State Management Libraries

Managing state across different platforms efficiently is crucial. Libraries like Decompose can help with hierarchical state management in a KMP environment.

Adding Dependency (Example with Decompose):

dependencies {
    implementation("com.arkivanov.decompose:decompose:2.4.0")
    implementation("com.arkivanov.decompose:extensions-compose:2.4.0")
}

ViewModel example using Decompose:

import com.arkivanov.decompose.ComponentContext
import com.arkivanov.decompose.value.MutableValue
import com.arkivanov.decompose.value.Value
import androidx.compose.runtime.*

interface MyComponent {
    val state: Value
    fun increment()
}

class MyComponentImpl(
    componentContext: ComponentContext
) : MyComponent, ComponentContext by componentContext {
    private val _state = MutableValue(0)
    override val state: Value = _state

    override fun increment() {
        _state.value = _state.value + 1
    }
}

@Composable
fun MyComposable(component: MyComponent) {
    val count by component.state.collectAsState()

    Button(onClick = { component.increment() }) {
        Text("Count: $count")
    }
}

Conclusion

Building Compose Multiplatform applications efficiently involves leveraging the right libraries. From UI components to asynchronous task handling, networking, data storage, and state management, the libraries discussed in this post can significantly streamline your development process and improve the robustness of your applications. By integrating these libraries effectively, you can ensure a cohesive and maintainable codebase across all supported platforms.