Compose Multiplatform App Debugging: Expert Guide for Jetpack Compose

Developing a multiplatform application with Jetpack Compose is an exciting way to share code across various platforms such as Android, iOS, Desktop, and Web. However, debugging can become challenging when dealing with multiple platforms and shared code. This post explores debugging strategies specific to Compose Multiplatform apps, providing best practices and examples to streamline your development process.

Understanding Compose Multiplatform Architecture

Before diving into debugging, it’s important to understand the architecture of a Compose Multiplatform application. These applications typically consist of:

• Shared Code: Contains the business logic, UI components (using Jetpack Compose), and other non-platform-specific code.
• Platform-Specific Code: Contains code that interacts with platform APIs and bootstraps the shared code for each platform (Android, iOS, Desktop, Web).

Debugging Strategies for Compose Multiplatform

Effective debugging in a Compose Multiplatform project requires a combination of strategies to handle issues in both shared and platform-specific code.

1. Logging and Tracing

Logging is a fundamental debugging technique. Implement comprehensive logging throughout your shared code to trace the flow of execution and identify potential issues.

Example (Kotlin):

import mu.KotlinLogging

private val logger = KotlinLogging.logger {}

fun processData(data: String) {
    logger.debug { "Processing data: $data" }
    try {
        // Your logic here
        if (data.isEmpty()) {
            logger.error { "Data is empty!" }
            throw IllegalArgumentException("Data cannot be empty")
        }
        logger.info { "Data processing successful." }
    } catch (e: Exception) {
        logger.error(e) { "Error processing data: ${e.message}" }
    }
}

In this example, we use KotlinLogging to log debug, info, and error messages. This can be adapted for any logging library you prefer.

2. Platform-Specific Debugging Tools

Leverage the debugging tools provided by each platform’s IDE (e.g., Android Studio for Android, Xcode for iOS). These tools allow you to set breakpoints, inspect variables, and step through code.

Debugging on Android

• Use Android Studio’s debugger to attach to the running process.
• Set breakpoints in both Kotlin/JVM and Compose code.
• Inspect variables in real-time.

Debugging on iOS

• Use Xcode to attach to the running iOS app.
• Set breakpoints in Swift/Objective-C code and Kotlin/Native code.
• Use Xcode’s console to view logs and error messages.

Debugging on Desktop (JVM)

• Use IntelliJ IDEA’s debugger to debug the Kotlin/JVM code.
• Set breakpoints and inspect variables as you would in a standard Kotlin/JVM application.

Debugging on Web (JavaScript)

• Use browser developer tools (Chrome DevTools, Firefox Developer Tools) to debug the Kotlin/JS code.
• Set breakpoints in the generated JavaScript code.
• Inspect variables and use console logging.

3. Unit and Integration Tests

Write unit tests for your shared code to verify the correctness of individual components and functions. Integration tests ensure that different parts of the system work together correctly.

Example (Kotlin Test):

import org.junit.Test
import kotlin.test.assertEquals

class DataProcessorTest {

    @Test
    fun `processData should handle valid data`() {
        val result = processData("Sample Data")
        assertEquals("Success", result)
    }

    @Test(expected = IllegalArgumentException::class)
    fun `processData should throw exception for empty data`() {
        processData("")
    }
}

Use JUnit or similar testing frameworks for JVM-based platforms and Kotlin/Native’s testing support for native targets.

4. Compose UI Inspection

Use the Compose UI Inspector to inspect the composable hierarchy, view component properties, and identify layout issues.

Steps to use Compose UI Inspector:

• Ensure your app is running in debug mode.
• Open the Layout Inspector in Android Studio (Tools > Layout Inspector).
• Select the running device/process.
• Inspect the Compose UI elements and their properties.

5. Conditional Compilation

Use conditional compilation to include or exclude code based on the target platform. This is useful for platform-specific debugging logic.

Example (expect/actual):

// Shared code
expect fun platformName(): String

// Android-specific implementation
actual fun platformName(): String = "Android"

// iOS-specific implementation
actual fun platformName(): String = "iOS"

In this example, platformName() returns a different value depending on the platform. You can use this to add platform-specific logging or debugging logic.

6. Network Inspection

For multiplatform apps that communicate with backend services, use network inspection tools to monitor HTTP requests and responses. Charles Proxy, Fiddler, and platform-specific tools (like Android Studio’s Network Inspector) can help you identify issues related to data serialization, API endpoints, and network connectivity.

7. Memory Leak Detection

Memory leaks can be a significant problem in multiplatform apps, especially on platforms with manual memory management (like iOS). Use memory profiling tools provided by each platform to detect and diagnose memory leaks.

• Android: Android Profiler in Android Studio.
• iOS: Instruments in Xcode.
• Desktop: Java VisualVM or IntelliJ Profiler.

Common Debugging Scenarios and Solutions

Scenario 1: UI Rendering Differences

Different platforms may render UI elements slightly differently due to variations in styling engines and rendering pipelines. Use platform-specific styling or conditional compilation to address these differences.

Scenario 2: Platform API Compatibility

Ensure that platform-specific API calls are correctly wrapped and handled. Use expect/actual declarations to provide platform-specific implementations of common interfaces.

Scenario 3: Asynchronous Operations

Asynchronous operations (e.g., coroutines, threads) can behave differently on different platforms. Use structured concurrency and thoroughly test asynchronous code on each target platform.

Scenario 4: Build Configuration Issues

Ensure that your build configurations are correctly set up for each platform. Pay attention to compiler flags, linker settings, and dependency management.

Best Practices for Debugging Compose Multiplatform Apps

• Consistent Logging: Maintain consistent logging practices across all platforms.
• Automated Testing: Implement a comprehensive suite of unit and integration tests.
• Platform-Specific Knowledge: Understand the nuances of each target platform’s debugging tools and techniques.
• Reproducible Builds: Ensure that your builds are reproducible to facilitate debugging and issue tracking.
• Community Resources: Leverage the Compose Multiplatform community for support, tips, and troubleshooting advice.

Conclusion

Debugging Compose Multiplatform applications requires a strategic approach that combines logging, platform-specific tools, automated testing, and a deep understanding of the underlying architecture. By adopting these strategies and best practices, you can efficiently identify and resolve issues, ensuring a smooth and productive development experience. Happy debugging!