An introduction to using the Dagger 2 dependency injection framework for Android applications. Brief explanation of dependency injection and a example of how to implement Dagger 2. Includes a real world example of Dagger 2

1. Todd Burgess
Todd Burgess Media
todd@toddburgessmedia.com
Twitter: @tburgess57
Github: toddburgessmedia
Introduction to Dagger 2
How to Dependency Inject a Kitten
An Introduction to Dagger 2

2. Give an object its instance variables
James Shore
Introduction to Dagger 2
Dependency Injection Definition

3. Introduction to Dagger 2
The Tail of 2 Constructors
class A {
B b;
public A () {
this.b = new B();
}
public A (B b) {
this.b = b;
}
}

4. Dagger 2 is a library that manages dependency injection in our Android
applications
Dagger 2 is maintained by Google and is a fork of Dagger 1 that was
done by Square
Introduction to Dagger 2
Dagger 2 Introduction

5. Introduction to Dagger 2
SharedPreferences Between Activities

6. Creates two objects when there only needs to be one
Code is duplicated across two activites
Introduction to Dagger 2
Problem with Current Example

7. Introduction to Dagger 2
Breaking SharedPreferences

8. Introduction to Dagger 2
If Only There Was a Way to Solve This

9. Introduction to Dagger 2
The Problem and the Desired Solution

10. Dagger 2 To the Rescue

11. 1)Create Modules to Provide Dependencies
1)Create Component to Link Modules to
Activities/Fragments
1)Create Component instance in Application
1)Inject dependencies into Activites/Fragments
Introduction to Dagger 2
Dagger 2 in a Nutshell

12. Dagger Demo
https://github.com/toddburgessmedia/Dagger2Demo

13. //Dagger 2 dependencies
compile 'com.google.dagger:dagger:2.11'
annotationProcessor 'com.google.dagger:dagger-compiler:2.11'
provided 'javax.annotation:jsr250-api:1.0'
Introduction to Dagger 2
Step 1
Add Dagger 2 Dependencies to build.gradle

14. Create the Module
AppModule.java

15. Create the Component
DemoComponent.java

16. Create the Application class
DemoApplication.java

17. Add DemoApplication to AndroidManifest.xml

18. Inject SharedPreferences
GreetingActivity.java

19. @Inject
lateinit var prefs : SharePreferences
Avoid null checks for dependency injected fields with lateinit
Introduction to Dagger 2
Dagger 2 and Kotlin
Lateinit for field injection

20. Introduction to Dagger 2
How to Dependency Inject a Kitten
Toronto Cat Rescue Kitten - Argo

21. Library by Square
Retrofit queries REST sources and returns the result as POJOs
Introduction to Dagger 2
Introduction to Retrofit

22. Get All Cats Available for Adoption Using Retrofit

23. Get Information About a Kitten

24. Introduction to Dagger 2
Using Dagger 2 to Dependency Inject a Kitten

25. Dagger 2 allows you the developer to focus more on writing code and
instead of maintaining it
Dagger 2 can be used to assist with testing and app frameworks (ex.
MVP)
Introduction to Dagger 2
In Conclusion

26. Adopt a Toronto Cat Rescue Cat
Alex – 1 Year old, Female

27. Dagger 2
https://google.github.io/dagger/
Retrofit
https://github.com/square/retrofit
Dagger 2 Demo
https://github.com/toddburgessmedia/Dagger2Demo
Toronto Cat Rescue
https://torontocatrescue.ca/
Introduction to Dagger 2
Links