Reducing APK size Christophe Beyls GDG Brussels

Why reduce the APK size? - Faster download times and less consumed data. (slow connections, costly/limited data fees) - Smaller install size on the device. (most entry-level phones only have 8 Gb of storage)

Also... Less bytecode means - Faster application startup (classloader). Especially when avoiding multidex. - Much smaller install size on the device. Lollipop & Marshmallow install size = 3-4x apk size - Faster installation on Lollipop & Marshmallow.

Inside an APK file - classes.dex: application bytecode. Sometimes more than one file (multidex). - lib/: folder with native libraries. Optional. - res/: folder with resources files. Images + binary XML files. (layouts, selector drawables, menus, anims, …) - resources.arsc: compiled resources tables - strings, colors, dimens, styles, ids. Uncompressed for faster access.

APK Analyzer in Android Studio 2.2

classes.dex

1. Optimize your dependencies Never include the full version of Google Play Services. dependencies { compile 'com.google.android.gms:play-services:9.0.2' } Only declare the modules you need. dependencies { compile 'com.google.android.gms:play-services-maps:9.0.2' compile 'com.google.android.gms:play-services-location:9.0.2' compile 'com.google.android.gms:play-services-gcm:9.0.2' }

1. Optimize your dependencies Choose lighter libraries. www.methodscount.com Example Dex Size: - Picasso 2.5.2 106 KB - Glide 3.7.0 403 KB - Fresco 0.9.0 1483 KB If possible, avoid libraries requiring large native binaries (.so files). Examples: Fresco, Realm.

1. Optimize your dependencies ./gradlew [app]:dependencies

2. Use Proguard for release builds android { buildTypes { release { minifyEnabled true proguardFiles getDefaultProguardFile(‘proguard-android. txt'), 'proguard-rules.pro' } } } - Big apps: multidex for debug, Proguard for release. - Add Proguard rules (if any) for each library you’re using. Many libraries already include Proguard rules inside their .aar file. - Avoid using reflection in your code. Else, add Proguard rules for it.

2. Use Proguard for release builds “I can’t read my stack traces anymore” 1. Lazy: add Proguard rule -dontobfuscate 2. Better: upload [app]/build/outputs/mapping/release/mapping.txt to Google Play Developer Console

lib/

If your app includes native binaries (.so files) 3. Split APK by CPU architecture Create one APK file for each CPU architecture. android { ... splits { abi { enable true reset() include 'x86', 'armeabi-v7a', 'mips' universalApk false } } }

res/

4. Remove unused resource files Very useful to remove unused parts of libraries. Requires Proguard. android { buildTypes { release { minifyEnabled true shrinkResources true proguardFiles getDefaultProguardFile('proguard-android. txt'), 'proguard-rules.pro' } } }

5. Optimize images - Manually optimize PNG (and JPEG) files using tools like Mac OS X: ImageOptim Linux: Trimage Windows: FileOptimizer. - Then disable automatic PNG optimization. Because it makes already optimized files bigger (issue 65335). android { aaptOptions { cruncherEnabled false } }

5. Optimize images - Replace JPEG files with lossy WebP files (Android 4+). Same quality, 33% smaller file size. - Replace small PNG icons with Vector Drawables and enable full VectorDrawable support in the support library 23.2+: android { defaultConfig { vectorDrawables.useSupportLibrary = true } } - More image optimizations: medium.com/@duhroach

resources.arsc

6. Remove unsupported locales - Libraries like AppCompat or Google Play Services include many strings in 75+ languages. - Specify the locales you support, the build tool will remove the rest. - Expect gaining a few hundred kilobytes. android { defaultConfig { ... resConfigs "en", "fr", "nl" } }

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