ProGuard and R8 optimization in Android Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of ProGuard in Android development?

ProGuard shrinks, optimizes, and obfuscates your app's code to reduce APK size and make reverse engineering harder.

intermediate

How does R8 differ from ProGuard?

R8 combines shrinking, optimization, and obfuscation in one step and is the default code shrinker in Android Studio since version 3.4.

beginner

What is a 'keep rule' in ProGuard or R8?

A keep rule tells the optimizer not to remove or rename certain classes or methods that are needed at runtime.

beginner

Why is obfuscation important in Android apps?

Obfuscation renames classes and methods to unreadable names, making it harder for others to understand or copy your code.

intermediate

When should you disable code shrinking in your Android app?

You might disable shrinking during debugging to speed up build times or if shrinking causes issues with reflection or libraries.

Which tool is the default code shrinker in Android Studio since version 3.4?

A R8

B ProGuard

C DexGuard

D Lint

R8 replaced ProGuard as the default shrinker and optimizer in Android Studio 3.4 and later.

What does a 'keep rule' in ProGuard or R8 do?

A Prevents removal or renaming of specified code

B Compresses images

C Removes unused code

D Generates logs

Keep rules protect code from being removed or renamed during shrinking and obfuscation.

Which of the following is NOT a benefit of using ProGuard or R8?

A Reducing APK size

B Improving app performance by optimizing code

C Making reverse engineering harder

D Automatically fixing runtime bugs

ProGuard and R8 do not fix runtime bugs automatically; they focus on shrinking, optimizing, and obfuscating code.

Why might you need to add keep rules when using R8?

A To speed up compilation

B To prevent removal of code used via reflection

C To enable multi-threading

D To increase APK size

Code accessed by reflection might be removed if not kept explicitly with keep rules.

What happens if you disable code shrinking in your Android app?

A Obfuscation is improved

B App runs faster

C App size usually increases

D App crashes immediately

Disabling shrinking keeps all code, which usually increases the app size.

Explain the roles of ProGuard and R8 in Android app optimization.

Think about how these tools help reduce app size and protect code.

Describe why and when you would use keep rules in your Android project.

Consider cases where code is used indirectly and must not be removed.