Dependency injection with Hilt in depth in Android Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Dependency Injection (DI) in Android development?

Dependency Injection is a design pattern that helps provide objects that a class needs (its dependencies) from outside rather than creating them inside the class. This makes code easier to test, maintain, and reuse.

beginner

What is Hilt and why is it used in Android?

Hilt is a library built on top of Dagger that simplifies dependency injection in Android apps. It provides standard components and annotations to reduce boilerplate and make DI easier to implement.

intermediate

Explain the role of @HiltAndroidApp annotation.

The @HiltAndroidApp annotation is placed on the Application class. It triggers Hilt's code generation and creates a base class that manages the app-level dependency container.

intermediate

How do you inject dependencies into an Android Activity using Hilt?

You annotate the Activity with @AndroidEntryPoint. Then, you can use @Inject on fields or constructor parameters to get dependencies automatically provided by Hilt.

intermediate

What is a Hilt Module and how do you define one?

A Hilt Module is a class annotated with @Module and @InstallIn that tells Hilt how to provide certain dependencies. Inside, you define functions annotated with @Provides that return the objects to inject.

Which annotation do you use to enable Hilt in your Application class?

A @AndroidEntryPoint

B @Inject

C @HiltAndroidApp

D @Module

The @HiltAndroidApp annotation is required on the Application class to start Hilt's code generation and setup.

How do you tell Hilt to inject dependencies into an Activity?

A Call inject() manually in onCreate()

B Annotate the Activity with @AndroidEntryPoint

C Use @Provides inside the Activity

D Annotate the Activity with @HiltAndroidApp

Annotating the Activity with @AndroidEntryPoint allows Hilt to generate the necessary code to inject dependencies.

What is the purpose of a Hilt Module?

A To store UI layout files

B To replace the Application class

C To annotate Activities for injection

D To provide instructions on how to create dependencies

Modules tell Hilt how to create and provide dependencies using @Provides functions.

Which annotation is used on a function inside a Hilt Module to provide a dependency?

A @Provides

B @Inject

C @Singleton

D @EntryPoint

@Provides marks a function that returns an object Hilt can inject.

What scope annotation would you use to make a dependency live as long as the Application?

A @Singleton

B @FragmentScoped

C @ActivityScoped

D @ViewModelScoped

@Singleton scope means the dependency lives as long as the Application instance.

Describe the steps to set up Hilt in an Android app and inject a dependency into an Activity.

Think about annotations on Application, Activity, and Modules.

Explain how Hilt manages the lifecycle of dependencies and what scopes are available.

Consider how different parts of the app need different lifetimes for objects.