MultiDexApplication in Android: why you need it and how to set it up

How to set up MultiDexApplication in a project

Integration MultiDexApplication consists of several steps. Here are step-by-step guide:

1. Add a dependency to build.gradle (module level):

   implementation 'androidx.multidex:multidex:2.0.1'

2. Enable multidex support in defaultConfig:

   android {
   defaultConfig {
   multiDexEnabled true
   }
   }

3. Create a descendant class (or change an existing one Application):

   public class MyApplication extends MultiDexApplication {
   @Override
   public void onCreate() {
   super.onCreate();
   // Your initialization code
   }
   }

4. Indicate your class in AndroidManifest.xml:

   <application
   android:name=".MyApplication"
   ...>

For projects on Kotlin the code will look like this:

class MyApp : MultiDexApplication() {
override fun onCreate() {
super.onCreate()
// Initialization
}
}

If you use ProGuard or R8, make sure that the obfuscation rules do not remove critical classes from additional .dexfiles. Add to proguard-rules.pro:

-keep class com.android.support.multidex.** { *; }

Project optimization: how to avoid MultiDexApplication

Before Instead of switching to multidex, try optimizing the project. Here are some effective ways to reduce the number of methods:

• 🧹 Remove unnecessary dependencies. Use ./gradlew :app:dependenciesto find and remove unused libraries.
• 🔄 Replace heavy libraries. For example, instead Guava use lighter alternatives.
• 📦 Use compileOnly for libraries needed only at the compilation stage.
• 🛠️ Include minifyEnabled and shrinkResources to remove unused code.

An example of dependency optimization in build.gradle:

dependencies {
// Instead of the full version of Firebase
implementation 'com.google.firebase:firebase-analytics-ktx'

// We use only the necessary modules
implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.6.2'
implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.6.2'

// compileOnly for annotations
compileOnly 'org.jetbrains:annotations:24.0.1'
}

Another effective way is to use Dynamic Feature Moduleswhich allows you to separate parts of the application into separate .apkfiles that are loaded on demand. This not only reduces the size of the main .dexfile, but also optimizes the loading of the application.

Typical problems with MultiDexApplication and their solutions

Even after correct configuration MultiDexApplication you may encounter problems. Here are the most common ones and ways to solve them:

⚠️ Attention: If you use Instant Run v Android Studio, multidex may be unstable. It is recommended to either disable Instant Runor use Apply Changes instead Apply Code Changes.

1. Error "No implementation found for ... "

This error occurs when a class from the main .dexfile tries to access a class from an additional .dexfile that has not yet been loaded. Solution:

• 🔧 Make sure that all critical classes (activities, services, providers) fall into the main .dexfile.
• 📝 Create a file multidex-config.pro or multidex-config.txt in directory app/ and indicate in it the classes that should be in the main .dexfile.

2. Increasing startup time

Loading multiple .dexfiles increases the cold start time. To reduce this time:

• ⚡ Use MultiDex.install(this) in attachBaseContext() instead of onCreate().
• 📉 Optimize the main .dexfile, leaving only the most necessary classes in it.

Example of optimized code:

public class MyApp extends MultiDexApplication {
@Override
protected void attachBaseContext(Context base) {
super.attachBaseContext(base);
MultiDex.install(this);
}
}

3. Problems with ProGuard/R8

If after enabling obfuscation the application stops working, check:

• 🔍 Rules proguard-rules.pro for conflicts with multidex.
• 📋 Build logs for warnings about deleted classes.

Add to proguard-rules.pro:

-keep class com.android.support.multidex.** { *; }
-keep public class * extends android.support.multidex.MultiDexApplication

⚠️ Attention: Work details ProGuard and R8 may change in new versions Android Gradle Plugin. Always check the latest settings in the official documentation.

Alternatives to MultiDexApplication

If you don't want to use MultiDexApplication, consider alternative approaches:

• 📦 Dynamic Feature Modules —allow you to break the application into modules that are loaded on demand. Supported with Android 5.0 (API 21).
• 🔄 App Bundles —a new publication format that automatically optimizes code delivery to users.
• 🧩 Micro-services —moving some of the functionality into separate services or libraries.
• 🗑️ Removing legacy code —cleaning the project of unused classes and libraries.

Configuration example Dynamic Feature Module in build.gradle:

android {
dynamicFeatures = [':dynamic_feature']
}

dependencies {
implementation project(':dynamic_feature')
}

App Bundles is a modern approach that not only solves the problem with the limit of methods, but also optimizes the size of the APK downloaded by the user. Google Play automatically generates optimized APKs for different devices.

To switch to App Bundles, change in build.gradle:

android {
bundle {
language {
enableSplit = true
}
density {
enableSplit = true
}
abi {
enableSplit = true
}
}
}

FAQ: Frequently asked questions about MultiDexApplication

./gradlew :app:analyzeDependencies

./gradlew :app:countDebugMethods

android {
buildTypes {
debug {
multiDexEnabled false
}
release {
multiDexEnabled true
}
}
}