In this Notes article, I roughly jotted down notes in English from the content of the English session video/podcast. This article is intended to be read as a reference while watching the video. I hope this article helps you even a little when you watch the actual video. (Please feel free to contact me if there are any errors or typos! m(__)m)

This article is based on An Opinionated Guide to Dependency Injection on Android (Android Dev Summit ‘19).

Dependency Injection

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Car needs engine to work = Engine is a dependency of car = Car depends on engine

• With dependency injection, those dependencies are provided to a class instead of the class creating them itself.

• You should always apply dependency injection principle to your app

  • sets fundamentals of testable and scalable app

  • Reusability of code

  • Good balance of loosely-coupled dependencies

  • Ease of refactoring

Dagger

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Recommendation

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• Does not use reflection

• Recommended tool

• Dagger is used on Gmail, Google Photos, Youtube

Steep learning curve..

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• Started providing a common guidance, which is a set of documentation from the basics to the complex topics

• Codelab for Dagger

dagger-android?

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• Google is stopping its development

• Adding no more feature

• Trying to reduce the amount of code you have to write

Better Dagger code with Kotlin

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Dagger + Kotlin = ♡

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• No more JvmStatic

• Qualifier Annotations

• Kotlin wildcards

Future versions

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• Some more improvements are coming

  • e.g. for companion object

Simple DI Approach in Android

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• still under construction

• how it will look like

  • Focus on binding declarations

Bindings

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The time you spend working on DI should really go to what you keep working on to scale your app.

Injection

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• Not just using @Inject, you should do some more extra work, for example to set up app component

• Add @EntryPoint for Android component class

  • Tells that you want this Android component to be a entry point into the graph

• Support and provide easy hookups for lifecycle related components like ViewModel

Components

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• Predefined Components

  • SingletonComponent

  • ActivityComponent

  • ServiceComponent

  • FragmentComponent

Jetpack DI Initiative

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• Integrated with Dagger

• Jetpack Extensions

  • Fragments

  • ViewModel

  • WorkManager

Takeaways

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• Use DI

• Use Dagger

• Check out the guidance

• We’re improving DI in Android, so stay tuned!

Impressions / Summary / Key Takeaways

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• They created a common guide.
  • It covers everything from basics to complex topics, so please check it out.
• They want to improve compatibility with Kotlin further.
  • Plans to include releases related to Companion Objects in future versions?
• Development of dagger-android has stopped for now.
  • Because they think it can be improved further.
• Aiming to lower setup and learning costs.
  • Mechanisms like adding @EntryPoint to Framework EntryPoints like Activities to create a graph from that class, automatically handling the Component setup in onCreate.
  • Mechanisms to make DI easier for other lifecycle-related AAC classes.
  • Providing common predefined Components without needing to define them yourself.

I got the message: DI is great, Dagger is great, we’ll keep making it better so please use it!

That’s all!