Dependency injection with Hilt in depth in Android Kotlin - Build, Publish & Deploy

Build & Publish - Dependency injection with Hilt in depth

Performance Impact

Using Hilt for dependency injection helps your app start faster by managing object creation efficiently. It avoids repeated manual object creation, reducing CPU work during runtime. This leads to smoother UI rendering and better battery life because objects are created only once and reused.

However, improper use of scopes or injecting heavy objects in the wrong place can increase memory use and slow down app startup.

Optimization Tips

• Use proper scopes (@Singleton, @ActivityScoped) to limit object lifetimes and avoid memory leaks.
• Inject only what you need; avoid injecting large objects into components that live long.
• Use constructor injection for easier testing and faster object creation.
• Keep modules small and focused to speed up compile time and reduce generated code size.
• Use @Provides methods only when constructor injection is not possible.

App Size and Startup Time

Hilt adds some generated code to your app, which slightly increases APK size, usually by a few hundred KB. This is small compared to the benefits of cleaner code and easier testing.

Startup time improves because Hilt manages dependencies efficiently, avoiding redundant object creation during app launch.

iOS vs Android Differences

Hilt is Android-specific and built on top of Dagger for Kotlin. iOS apps use different dependency injection patterns, often manual or with Swift frameworks like Swinject.

Android apps benefit from Hilt's compile-time injection and annotation processing, which is not available on iOS.

Store Review Guidelines

• Ensure your app does not delay startup excessively; Hilt helps by efficient injection.
• Do not include unused dependencies or modules to keep app size small.
• Follow Android's security best practices when injecting sensitive data.
• Make sure your app handles configuration changes properly with scoped components.

Self Check

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

• You might be injecting heavy or many dependencies in the wrong scope, causing slow initialization.
• Modules may be too large or complex, increasing compile and runtime overhead.
• Objects might be recreated unnecessarily instead of being scoped as singletons.
• Check if you are doing heavy work on the main thread during injection.

Key Result

Using Hilt for dependency injection improves app startup and runtime performance by managing object creation efficiently, but requires careful scope management to avoid memory overhead and slow loading.