Mastering Dagger Hilt: A Key to Success in Android Interviews

Hitesh Kohli
7 min readJul 16, 2023
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In Android development, dependency injection is a crucial concept that helps manage dependencies and promotes code modularity. Dagger Hilt, a powerful library, offers an easier approach to implementing dependency injection in Android applications.

In this blog, I will demystify Dagger Hilt, exploring its purpose, relationship with Dagger 2, and its growing prominence as a standard for dependency injection.

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Importance of Understanding Dagger Hilt:

Dagger Hilt’s importance lies in its ability to simplify the complex setup of Dagger 2, its predecessor. By introducing the concept of layered components, Dagger Hilt eliminates the need for multiple components, making dependency injection more accessible and intuitive. This improved approach streamlines the management of dependencies and promotes a modular architecture.

Understanding Dagger Hilt:

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Dagger Hilt serves as a library that simplifies the implementation of dependency injection in Android projects. It builds upon the foundations of Dagger 2, another popular dependency injection framework.

With Dagger Hilt, developers can embrace the benefits of dependency injection without dealing with the complexities of Dagger 2 directly.

Key Features of Dagger Hilt:

  1. Simplicity: Dagger Hilt provides a more intuitive and streamlined approach to dependency injection, making it easier to grasp and implement.
  2. Wrapper around Dagger 2: The hilt acts as a convenient wrapper around Dagger 2, abstracting away its complexities and reducing boilerplate code.
  3. Standard Implementation: With its growing popularity, Dagger Hilt has become the preferred choice for implementing dependency injection in Android projects.
  4. Code Generation: Behind the scenes, Dagger Hilt generates Dagger code to handle dependency injection, automating the process for developers.

Dagger Hilt simplifies the implementation of dependency injection in Android development. While knowing Dagger 2 can be advantageous, it is not a prerequisite to benefit from Dagger Hilt.

Getting Started with Dagger Hilt:

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To start implementing Dagger Hilt in your Android app, you need to follow a few key steps:

  1. Add Dependencies: Include the necessary Dagger Hilt dependencies in your app’s build. gradle file.
  2. Kotlin-Kapt Plugin: Enable the Kotlin Annotation Processing Tool (Kapt) plugin to process Dagger Hilt annotations during the build process.
  3. Leverage Annotations: Utilize Dagger Hilt annotations, similar to how they are used in Dagger 2, to define and inject dependencies throughout your app.
  4. Benefit from Simplified Dependency Injection: With Dagger Hilt in place, the framework takes care of object creation and dependency resolution, reducing boilerplate code and making your codebase more maintainable.

How Dagger Hilt simplifies Dagger 2:

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Standardized Annotations in Dagger Hilt:

One of the key advantages of Dagger Hilt is the provision of standardized annotations. Unlike Dagger 2, where you may need to define your custom annotations, Dagger Hilt comes with a set of predefined annotations that simplify the dependency injection process. These annotations serve as a layer on top of other annotations, providing a more intuitive and standardized approach to dependency injection.

Layer-Based Approach:

Dagger Hilt employs a layer-based approach in its annotation system. This means that there is a parent annotation and other annotations that inherit from the parent. By utilizing this approach, Dagger Hilt eliminates the need to define multiple custom annotations, reducing complexity and improving code readability.

Exploring Documentation for In-Depth Understanding:

To fully grasp the benefits of Dagger Hilt’s streamlined approach, it is recommended to refer to the official documentation. The documentation provides detailed explanations of the annotations and their usage, enabling developers to leverage Dagger Hilt’s streamlined features effectively.

Concept of Layered Components in Hilt:

Layered components in Dagger Hilt allow for modular architecture. The SingletonComponent represents the top-level component, which is applicable in the application context. However, Hilt also enables the creation of ActivityComponent or FragmentComponent as per specific requirements. This flexibility ensures that dependencies are scoped correctly and promotes efficient object creation.

What is @ HiltAndroidApp ?

The @HiltAndroidApp annotation serves as a crucial component in Dagger Hilt’s architecture. It is placed in the application class (application Context) to signify the entry point for Dagger Hilt in your Android app. By adding this annotation, you provide a reference to the application context, which other Dagger Hilt annotations can access.

Behind the scenes, the @HiltAndroidApp annotation triggers the generation of Dagger code required for dependency injection.

The inclusion of the @HiltAndroidApp annotation is a crucial step in setting up Dagger Hilt in your Android app. It acts as a gateway for Dagger Hilt, allowing other annotations to access the application context seamlessly.

What is @ AndroidEntryPoint?

The @AndroidEntryPoint annotation serves as a crucial element in Dagger Hilt’s integration process. It is placed on top of the main activity in your Android app, indicating the entry point for dependency injections. By applying this annotation, you inform Dagger Hilt about the class where dependencies need to be injected.

When using @AndroidEntryPoint, it is important to maintain consistency in the usage of this annotation. If a class is annotated with @AndroidEntryPoint and other classes depend on it, those dependent classes must also have the @AndroidEntryPoint annotation. This ensures that the entire dependency graph is properly set up for injection.

What is @ Inject?

@Inject means if you want to build a particular object, execute this constructor. @Inject allows Dagger Hilt the information needed to build that object.

What is @ Module?

The @Module annotation in Dagger Hilt serves as a directive to inform the framework that a particular class will be used to provide dependencies. By annotating a class with @Module, you create a module specifically designed to define the dependencies that will be used in the application.

@Module allows developers to customize the dependency injection process by defining specific dependencies and their respective providers. Inside a module, you can use the @Provides annotation to define methods that generate instances of dependencies.

What is InstallIn(SingletonCompoenent::Class)?

The use of InstallIn(SingletonComponent: class) is particularly valuable when dealing with dependencies that are expensive to create or should be shared across the entire application. By scoping such dependencies within the Singleton Component, Dagger Hilt ensures that they are created only once and reused throughout the application’s lifespan. This optimization can greatly improve performance and resource usage, especially in scenarios such as Retrofit calls or heavy object creation.

What is @ Binds?

By utilizing @Binds, developers can streamline the process of binding interfaces to their respective implementations. Unlike traditional methods that involve using @Provides and creating instances within modules, @Binds eliminates the need for instantiating the implementation class explicitly. Instead, it establishes a direct binding between the interface and the implementation, reducing boilerplate code and simplifying the overall configuration.

Summary of Key Points:

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  1. Dagger Hilt simplifies dependency injection by introducing layered components, such as the Singleton Component, enabling efficient object creation and management.
  2. The InstallIn(SingletonComponent::class) annotation signifies the seamless integration of Dagger Hilt and represents an improvement over the complexity of Dagger 2.
  3. The Singleton Component specializes in scoping dependencies within the Application Context, while ActivityComponent and FragmentComponent allow for more granular dependency management.
  4. Dagger Hilt’s injection process involves initial checks for @Inject constructors, searching for @Provides within relevant components, and utilizing the Singleton Component for object creation and injection.

By delving into the depths of Dagger Hilt, You have gained the ability to efficiently manage dependencies, enhance code quality, and optimize application performance.



Hitesh Kohli

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