This is a simple introduction into achieving dependency injection on android using the dagger2 framework.

1. DAGGER SO SHARP!
DEPENDENCY INJECTION IN ANDROID

2. TOPICS
 What is Dependency Injection
 What is Dagger
 Pros and Cons of Dagger
 Dagger alternatives
 Sample Implementation
 QA session

3. WHAT IS DEPENDENCY INJECTION?
 Dependency Injection (DI) is a design pattern used to implement Inversion of Control(IoC). It allows the
creation of dependent objects outside of a class and provides those objects to a class through different
ways. Using DI, we move the creation and binding of the dependent objects outside of the class that
depends on them.
 It's a design pattern(No need for a library to implement)
 We all use some form of DI
Car Engine
Dependency
Depends

4. DEPENDENCY INJECTION PATTERN
CLIENT
INJECTOR
SERVICE
Uses

5. HARD COUPLED
EXAMPLE
 BadCar is tightly coupled to
the fate of Engine and
Wheels

6. BENEFITS OF DI
LOOSE COUPLING EASY TO TEST CODE REUSABILITY

7. TYPES OF DI
Constructor
injection
Field
injection
Method
injection

9. POPULAR
LIBRARIES
 Dagger2
 Koin
 Kodein
 Roboguice
 Butterknife
 Android annotation
 Toothpick

10. WEAPONS,
MONEY AND
DRUGS
A SIDE BY SIDE
COMPARISON OF
DAGGER2, KOIN
AND KODEIN

11. COMPARISON BETWEEN DAGGER2, KOIN & KODEIN
Dagger 2 Koin Kodein
Written in Java Written in kotlin Written in Kotlin(Java support)
Generates code in build does not generate code(less
build time)
No code generation
Has proxy classes No proxy classes No proxy classes
Uses annotations No annotation No annotation
A lot of boilerplate Less boilerplate

12. DAGGER2
Car
Engine
Plugs Starter
Wheels
Tires Nuts
Driver

13. DAGGER2
 Uses Directed Acyclic Graph = DAGger
 There are no cyclic dependencies
 @Module and @Provides: define classes and methods which provide dependencies
 @Inject: request dependencies. Can be used on a constructor, a field, or a method
 @Component: enable selected modules and used for performing dependency injection

14. LET'S ROLL UP
OUR SLEEVES
AND WRITE
SOME CODE!

15. BENEFITS OF DAGGER2
 Provides compile-time verification of the whole dependency graph so app doesn't crash at runtime
 Very clear error messages
 Designed for low-end devices

16. CONS OF DAGGER2
 Too verbose
 Steep learning curve

17. INTERACTIVE QA
SESSION
ASK AWAY

18. THANK YOU THE END. THAT'S IT.

19. REFERENCES &
FURTHER
READING
 https://codinginflow.com/tutorials/android/dagger-2/part-1-introduction
 https://www.tutorialsteacher.com/ioc/dependency-injection
 https://android.jlelse.eu/fundamentals-of-dependency-injection-and-
popular-libraries-in-android-c17cf48b5253
 https://medium.com/@egek92/koin-di-comparison-of-android-dependency-
injection-frameworks-236a6909bc3e
 https://dagger.dev/users-guide
 https://medium.com/@charbgr/bye-bye-dagger-1494118dcd41
 https://www.journaldev.com/20654/android-mvp-dagger2-retrofit-rxjava
 https://android.jlelse.eu/7-steps-to-implement-dagger-2-in-android-
dabc16715a3a
 https://www.vogella.com/tutorials/Dagger/article.html
 https://blog.mindorks.com/introduction-to-dagger-2-using-dependency-
injection-in-android-part-2-b55857911bcd
 https://medium.com/@harivigneshjayapalan/dagger-2-for-android-
beginners-introduction-be6580cb3edb
 https://www.youtube.com/watch?v=ZZ_qek0hGkM
 https://medium.com/dvt-engineering/android-dagger-2-isnt-hard-
97671ac15b07

20. DAGGERING
NEVER STOP
I HAD TO ADD THIS