Android ProGuard/R8 Setup

Configures ProGuard/R8 code minification and resource shrinking with safe default rules.

Prerequisites

• Android project with Gradle
• Kotlin DSL (build.gradle.kts)

Inputs

Process

Step 1: Create ProGuard Rules File

Create or update app/proguard-rules.pro with safe defaults:

cat > app/proguard-rules.pro << 'EOF'
# Add project specific ProGuard rules here.
# By default, the flags in this file are appended to flags specified
# in the Android SDK.

# Keep line numbers for debugging stack traces
-keepattributes SourceFile,LineNumberTable

# Hide the original source file name
-renamesourcefileattribute SourceFile

# Keep data classes and their fields
-keepclassmembers class * {
    @kotlinx.serialization.SerialName <fields>;
}

# Keep Parcelables
-keepclassmembers class * implements android.os.Parcelable {
    public static final android.os.Parcelable$Creator *;
}

# Keep custom views
-keep public class * extends android.view.View {
    public <init>(android.content.Context);
    public <init>(android.content.Context, android.util.AttributeSet);
    public <init>(android.content.Context, android.util.AttributeSet, int);
}

# Keep native methods
-keepclasseswithmembernames class * {
    native <methods>;
}
EOF

Note: If proguard-rules.pro already exists, ask the user if they want to:

• Replace with safe defaults
• Append safe defaults to existing rules
• Keep existing rules as-is

Step 2: Enable Minification in build.gradle.kts

Update app/build.gradle.kts to enable ProGuard/R8:

android {
    // ... existing config ...

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

Detection logic:

• Check if buildTypes.release already exists
• Check if isMinifyEnabled is already set
• Preserve existing proguardFiles if present, append if needed

Verification

MANDATORY: Run these commands:

# Verify ProGuard rules file exists
test -f app/proguard-rules.pro && echo "✓ ProGuard rules exist"

# Verify minification is enabled
grep "isMinifyEnabled = true" app/build.gradle.kts && echo "✓ Minification enabled"

# Verify resource shrinking is enabled
grep "isShrinkResources = true" app/build.gradle.kts && echo "✓ Resource shrinking enabled"

Expected output:

• ✓ ProGuard rules exist
• ✓ Minification enabled
• ✓ Resource shrinking enabled

Outputs

Troubleshooting

"Build fails with ProGuard error"

Cause: ProGuard removed required classes Fix: Add keep rules for the failing classes to proguard-rules.pro

"App crashes on release but not debug"

Cause: ProGuard obfuscated code that uses reflection Fix: Add keep rules for classes used via reflection

Library-Specific ProGuard Rules

Add these rules based on your project dependencies:

Retrofit/OkHttp

-keepattributes Signature
-keepattributes *Annotation*
-keep class okhttp3.** { *; }
-keep interface okhttp3.** { *; }
-dontwarn okhttp3.**
-keepattributes Signature, InnerClasses, EnclosingMethod
-keepclassmembers,allowshrinking,allowobfuscation interface * {
    @retrofit2.http.* <methods>;
}

Gson

-keepattributes Signature
-keepattributes *Annotation*
-keep class com.google.gson.** { *; }
-keep class * implements com.google.gson.TypeAdapterFactory
-keep class * implements com.google.gson.JsonSerializer
-keep class * implements com.google.gson.JsonDeserializer
-keepclassmembers,allowobfuscation class * {
    @com.google.gson.annotations.SerializedName <fields>;
}

Kotlin Serialization

-keepattributes *Annotation*, InnerClasses
-dontnote kotlinx.serialization.AnnotationsKt
-keepclassmembers class kotlinx.serialization.json.** {
    *** Companion;
}

Health Connect

-keep class androidx.health.connect.client.** { *; }
-keep class androidx.health.platform.client.** { *; }

Room

-keep class * extends androidx.room.RoomDatabase
-keep @androidx.room.Entity class *

ProGuard Test Configuration

Important: Test libraries should NEVER be in release builds. They are androidTestImplementation only.

If you need to run instrumented tests on release builds (e.g., to verify signing), use a separate test ProGuard file:

Step 1: Create app/proguard-rules-androidTest.pro:

# Keep EVERYTHING in test APK - we only care about signing, not size
-dontobfuscate
-dontoptimize
-dontshrink
-keep class ** { *; }

Step 2: Update app/build.gradle.kts:

android {
    buildTypes {
        release {
            isMinifyEnabled = true
            signingConfig = signingConfigs.getByName("release")
            proguardFiles(
                getDefaultProguardFile("proguard-android-optimize.txt"),
                "proguard-rules.pro"
            )
            // Keep-all rules for test APK only
            testProguardFiles("proguard-rules-androidTest.pro")
        }
    }
    testBuildType = "release"
}

Result:

• App APK: Minified with release key ✅
• Test APK: Not minified, signed with release key ✅
• Both have matching signatures for instrumentation ✅

Completion Criteria

• app/proguard-rules.pro exists with safe defaults
• isMinifyEnabled = true in app/build.gradle.kts
• isShrinkResources = true in app/build.gradle.kts
• ProGuard rules syntax is valid