Efficient Logging in Kotlin with ProGuard Optimization

In Android development, logging is crucial for debugging and monitoring your application. However, excessive logging in production can expose sensitive data, increase APK size, and degrade performance. This guide will walk you through creating a powerful yet lightweight logging system in Kotlin, ensuring logs are automatically removed in release builds using ProGuard.

Key Features of the Logging System

🔹 Automatic class name, method name, and line number detection.

🔹 Supports multiple log levels: DEBUG, INFO, WARN, and ERROR.

🔹 Automatically disabled in release builds for performance and security.

🔹 Clickable log links for quick navigation in Android Studio.

Step 1: Create a Custom Logging Utility

To simplify your logging process and maintain clean code, create a reusable log function.
LogUtil.kt :-

object LogUtil {

    enum class LogType { DEBUG, INFO, WARN, ERROR }

    fun log(keyName: String, value: Any?, type: LogType = LogType.DEBUG) {
        if (!BuildConfig.DEBUG) return  // Only log in DEBUG mode
        val stackTrace = Throwable().stackTrace[1] // Caller information
        val tag = stackTrace.className.substringAfterLast(".")  // Auto Class Name
        val fileName = stackTrace.fileName                      // File Name for clickable link
        val methodName = stackTrace.methodName                  // Auto Method Name
        val lineNumber = stackTrace.lineNumber                  // Auto Line Number

        val dataType = value?.let { it::class.simpleName } ?: "null"

        val logMessage = "($fileName:$lineNumber) ➔ $keyName ($dataType) = $value"

        when (type) {
            LogType.DEBUG -> Log.d(tag, logMessage)
            LogType.INFO -> Log.i(tag, logMessage)
            LogType.WARN -> Log.w(tag, logMessage)
            LogType.ERROR -> Log.e(tag, logMessage)
        }
    }
}

Example Usage in MainActivity

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val appName = "Kotlin App"
        val versionCode = 1
        val isPremiumUser = true
        val userList = listOf("Alice", "Bob", "Charlie")

        LogUtil.log("appName", appName, LogType.DEBUG)
        LogUtil.log("versionCode", versionCode, LogType.INFO)
        LogUtil.log("isPremiumUser", isPremiumUser, LogType.WARN)
        LogUtil.log("userList", userList, LogType.ERROR)
    }
}

Sample Log Output in Logcat

In this screenshot, clicking on MainActivity:86 in Logcat directly opens the corresponding file and line number in your IDE, enhancing development efficiency.

Step 2: Add ProGuard Rules to Remove Logs

ProGuard is a powerful tool that optimizes and obfuscates your code. By adding a ProGuard rule, you can ensure that all Log statements are stripped from the release build.
proguard-rules.pro :-

# Remove all Log statements in release builds
-assumenosideeffects class android.util.Log {
    public static int d(...);
    public static int i(...);
    public static int w(...);
    public static int e(...);
    public static int v(...);
    public static int println(...);
}

Step 3: Add ProGuard File in build.gradle.kts

Ensure your build.gradle.kts file includes ProGuard configuration in the release build type.
build.gradle.kts (app) :-

buildTypes {
    release {
        isMinifyEnabled = true
        isShrinkResources = true
        proguardFiles(
            getDefaultProguardFile("proguard-android-optimize.txt"),
            "proguard-rules.pro"
        )
    }
}

Step 4: Clean & Rebuild

1. Clean Project ➔ Build > Clean Project
2. Rebuild Project ➔ Build > Rebuild Project(Clean and Assemble project with tests)
3. Generate Release APK ➔ Build > Generate Signed APK

Step 5: Outcome

✅ Debug Build Variant: Logs will appear as usual.
✅ Release Build Variant: Logs will be removed automatically for better performance and security.

This method is effective, lightweight, and ensures no accidental logs leak into your production build. 🚀

Happy coding!

If you’re interested in learning more about Kotlin Multiplatform and Compose Multiplatform, check out my playlist on YouTube Channel:
Mastering Kotlin Multiplatform with Jetpack Compose: Complete Guide in Hindi

Thank you for reading! 🙌🙏✌ I hope you found this guide useful.

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Explore More Projects

If you’re interested in seeing full applications built with Kotlin Multiplatform and Jetpack Compose, check out these open-source projects:

• News Kotlin Multiplatform App (Supports Android, iOS, Windows, macOS, Linux):
  News KMP App is a Kotlin Compose Multiplatform (KMP) project that aims to provide a consistent news reading experience across multiple platforms, including Android, iOS, Windows, macOS, and Linux. This project leverages Kotlin’s multiplatform capabilities to share code and logic while using Compose for UI, ensuring a seamless and native experience on each platform.
  GitHub Repository: News-KMP-App
• Gemini AI Kotlin Multiplatform App (Supports Android, iOS, Windows, macOS, Linux, and Web):
  Gemini AI KMP App is a Kotlin Compose Multiplatform project designed by Gemini AI where you can retrieve information from text and images in a conversational format. Additionally, it allows storing chats group-wise using SQLDelight and KStore, and facilitates changing the Gemini API key.
  GitHub Repository: Gemini-AI-KMP-App

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