proguard-r8-without-gradle

SKILL: ProGuard / R8 Without Gradle

Key insight: R8 is already inside d8.jar!

You do NOT need to download ProGuard or R8 separately. Google's R8 compiler (which replaced ProGuard in all modern Android builds) is bundled inside d8.jar from the Android SDK build-tools. Same jar, different main class:

# D8 mode — just converts .class → .dex (no shrinking)
java -cp d8.jar com.android.tools.r8.D8 ...

# R8 mode — shrinks + obfuscates + converts .class → .dex
java -cp d8.jar com.android.tools.r8.R8 ...

R8 does everything ProGuard does plus DEX conversion in one step — no separate ProGuard pass needed.

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What R8 does

Feature	Result
Tree shaking	Removes unused classes, methods, fields
Obfuscation	Renames classes/methods to a, b, c...
Minification	Removes debug info, line numbers
DEX conversion	Outputs classes.dex directly

Typical size reduction on a real app: 30-50%. On already-minimal apps (like a 16KB Tetris): 15-27% — most of the weight is APK structure and signing overhead.

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ProGuard config file

Create proguard.pro — tells R8 what to keep (don't obfuscate entry points):

# Keep all Android entry points
-keep public class * extends android.app.Activity
-keep public class * extends android.app.Service
-keep public class * extends android.view.View
-keep public class * extends android.view.SurfaceView

# Keep lifecycle methods on Activities
-keepclassmembers class * extends android.app.Activity {
    protected void onCreate(android.os.Bundle);
    protected void onDestroy();
    protected void onPause();
    protected void onResume();
    protected void onActivityResult(int, int, android.content.Intent);
}

# Keep SurfaceView callbacks
-keepclassmembers class * extends android.view.SurfaceView {
    public void surfaceCreated(android.view.SurfaceHolder);
    public void surfaceDestroyed(android.view.SurfaceHolder);
    public void surfaceChanged(android.view.SurfaceHolder, int, int, int);
    public boolean onTouchEvent(android.view.MotionEvent);
}

# Keep View constructors (needed for inflation)
-keepclassmembers class * extends android.view.View {
    public <init>(android.content.Context);
    public <init>(android.content.Context, android.util.AttributeSet);
}

# Don't warn about missing classes from android.jar stubs
-dontwarn **

# Allow R8 to make members more accessible for optimization
-allowaccessmodification

# Skip preverification (not needed for Android/DEX)
-dontpreverify