Reduce APK size

I) Shrink Code and Resources

Shrink Code

use minifyEnabled true

android {
    ...
    buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'),
                    'proguard-rules.pro'
        }
    }
}

• It will remove unused code of own app and library and also obfuscates the class, variable, method with short name base on proguard config when build project.
• After shrink, it will output some files for the details of the shrinking so if you want to verify shrinking is correct you can check that files (check docs for more details)
• Sometime, shrinking remove some code that we don’t want to remove so we can custom the remove files by custom the proguard

Some noted

• Shrinking code is disable when we use Instant Run, to enable it check the (check docs for more details)

Shrink Resources

use shrinkResources true

android {
    ...
    buildTypes {
        release {
            shrinkResources true
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'),
                    'proguard-rules.pro'
        }
    }
}

• It will remove unused resource of own app and library
• We can remove some unused resource of some specific density by build multiple APK.

Build multiple APK

use splits in gradle

android {  
    splits {  
           ...          
    }         
} [check the docs here](https://developer.android.com/studio/build/configure-apk-splits.html)

II) Use Drawable object instead of image

• Use shape
• Use vector image

III) Reused resource

• Use android:rotate for rotate image
• Use android:tint for change the color of image

IV) Avoid enumerations

Enum take more size when build, if possible use @IntDef, @StringDef annotation