App size optimization in Android Kotlin - Build, Publish & Deploy

Build & Publish - App size optimization

Performance Impact

Optimizing app size helps your app load faster and use less memory. Smaller apps start quicker, improving user experience. It also reduces battery drain because less data is processed during startup. A smaller app is easier to keep smooth at 60 frames per second, especially on low-end devices.

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How to Optimize for 60fps Rendering

Remove unused resources like images and code. Use Android App Bundles to deliver only needed parts to each device. Compress images and use vector graphics when possible. Avoid large libraries if you only need small features. Enable ProGuard or R8 to shrink and optimize your code. These steps reduce work during app startup and UI rendering, helping maintain smooth animations.

Impact on App Bundle Size and Startup Time

Reducing app size lowers download time and storage use. Smaller apps start faster because less code and fewer resources load into memory. This is important for users with slow internet or limited storage. Using Android App Bundles can reduce APK size by up to 30-50%. Optimized images and code shrinking can further cut size, improving startup speed and responsiveness.

iOS vs Android Differences

On Android, App Bundles (.aab) allow dynamic delivery of resources, reducing install size per device. iOS uses App Thinning with slicing and on-demand resources to achieve similar results. Android requires signing with a keystore and supports multiple APKs for different device configurations. iOS apps are signed with certificates and provisioning profiles. Both platforms benefit from code and resource optimization but use different tools and processes.

Store Review Guidelines and Requirements

Google Play requires apps to be signed with a valid keystore and recommends using App Bundles for smaller downloads. Apple App Store requires code signing with valid certificates and recommends App Thinning to reduce app size. Both stores check for excessive permissions and large unused resources that can affect user trust and app performance. Follow platform guidelines to avoid rejection and ensure smooth user experience.

Self-Check: Your app takes 5 seconds to load this screen. What's likely wrong?

Possible issues include large uncompressed images, unused libraries increasing app size, or no code shrinking enabled. The app might be loading too many resources at startup instead of on demand. Check if ProGuard/R8 is enabled and if Android App Bundles are used. Optimizing these areas can reduce load time and improve performance.

Key Result

Optimizing app size improves startup speed, reduces memory use, and helps maintain smooth UI at 60fps. Use Android App Bundles, code shrinking, and resource optimization to deliver smaller, faster apps that meet store requirements.

Practice

1. What is the main purpose of enabling minifyEnabled in an Android app's build configuration?

easy

A. To add more debugging information

B. To increase the app's runtime speed

C. To remove unused code and reduce the app size

D. To enable multi-language support

Solution

1. Step 1: Understand minifyEnabled role

   This setting activates code shrinking tools like ProGuard or R8 to remove unused code.

2. Step 2: Effect on app size

   Removing unused code reduces the final APK or AAB size, making the app smaller.

3. Final Answer:

   To remove unused code and reduce the app size -> Option C

4. Quick Check:

   minifyEnabled = Remove unused code [OK]

Hint: minifyEnabled removes unused code to shrink app size [OK]

Common Mistakes:

• Thinking it improves runtime speed directly
• Confusing it with enabling debugging
• Assuming it adds features like language support

2. Which of the following is the correct way to enable resource shrinking in your build.gradle file for an Android app?

easy

A. shrinkResources = true

B. shrinkResources()

C. shrinkResources: true

D. shrinkResources true

Solution

1. Step 1: Check Gradle syntax for booleans

   In Gradle Groovy DSL, boolean properties are set with property true syntax.

2. Step 2: Apply to shrinkResources

   The correct syntax is shrinkResources true inside the buildTypes block.

3. Final Answer:

   shrinkResources true -> Option D

4. Quick Check:

   Gradle boolean syntax = property true [OK]

Hint: Use `property true` syntax in build.gradle (Groovy) [OK]

Common Mistakes:

• Using equals sign (Kotlin DSL)
• Using colon instead of space
• Calling it like a function

3. Given this build.gradle snippet, what will be the effect on the app size?

buildTypes {
  release {
    minifyEnabled true
    shrinkResources true
  }
}

medium

A. App size will increase due to added debugging info

B. App size will decrease by removing unused code and resources

C. App size will remain the same

D. App will fail to build due to syntax error

Solution

1. Step 1: Analyze minifyEnabled true

   This enables code shrinking tools to remove unused code.

2. Step 2: Analyze shrinkResources true

   This removes unused resources like images and strings from the APK.

3. Step 3: Combined effect on app size

   Both together reduce app size by removing unused code and resources.

4. Final Answer:

   App size will decrease by removing unused code and resources -> Option B

5. Quick Check:

   minifyEnabled + shrinkResources = smaller app [OK]

Hint: Both flags together shrink code and resources [OK]

Common Mistakes:

• Thinking it adds debugging info
• Assuming no effect on size
• Confusing syntax causing build failure

4. You enabled minifyEnabled true and shrinkResources true but your app crashes on startup. What is the most likely cause?

medium

A. You forgot to add ProGuard rules to keep necessary classes

B. You did not enable debugging mode

C. You used wrong syntax in build.gradle

D. You did not update your Android Studio version

Solution

1. Step 1: Understand minify effect on code

   Minify removes unused code but can mistakenly remove needed classes if rules are missing.

2. Step 2: Importance of ProGuard rules

   Proper rules keep essential classes from removal, preventing crashes.

3. Final Answer:

   You forgot to add ProGuard rules to keep necessary classes -> Option A

4. Quick Check:

   Missing ProGuard rules cause crashes after minify [OK]

Hint: Always add ProGuard rules when minifying [OK]

Common Mistakes:

• Blaming debugging mode
• Assuming syntax error without checking logs
• Ignoring ProGuard configuration

5. You want to reduce your Android app size by removing unused resources but keep some images used only in code via reflection. How should you configure your build to avoid removing these images?

hard

A. Add keep rules in proguard-rules.pro to keep resource references

B. Disable shrinkResources and rely only on minifyEnabled

C. Rename the images to start with underscore to protect them

D. Use shrinkResources with resConfigs to specify languages only

Solution

1. Step 1: Understand resource shrinking behavior

   Resource shrinking removes unused resources detected by static analysis.

2. Step 2: Handling resources used via reflection

   Resources accessed dynamically may appear unused and get removed unless explicitly kept.

3. Step 3: Use ProGuard keep rules

   Adding keep rules in proguard-rules.pro tells the shrinker to keep these resources.

4. Final Answer:

   Add keep rules in proguard-rules.pro to keep resource references -> Option A

5. Quick Check:

   Keep rules protect resources used dynamically [OK]

Hint: Use keep rules to protect resources used by reflection [OK]

Common Mistakes:

• Disabling shrinkResources loses size benefits
• Renaming files does not protect them
• Using resConfigs only filters languages, not resources