What is dependency injection principle in programming. What are its usages and where to use it? Dependency inversion principle. How to implement DI in Android. Dagger2 framework in Android. Android app development with Dagger2. Scope and components. Must use framework for Android developers.

1. Dependency
injection
AND DAGGER2 FRAMEWORK IN ANDROID

2. WHAT IS DEPENDENCY?

3. INJECTION
 Push dependency from outside into the class.
• Fetch dependency
• Receive dependency

4. DI
 Ask third party to create object, instead of create dependencies
yourself.

5. WHY NEED DI
 Decouple classes construction from construction of your
dependency.

6. DEPENDENCY INVERSION PRINCIPLE
Class Dependency
Interface
Implementation
Dependen
cy

7. DI CONTAINER
 Create and map dependency

8. DI LIBRARY FOR ANDROID
• Dagger 2

9. Dagger 2
 Dagger 2 analyzes dependencies for you and generates code to
help wire them together.

10. WITHOUT DAGGER 2
Activities
Fragments
Views
Objects
API interface
(Retrofit)
Image Loader
(Picasso)
Shared
Preference
Network client
Image disk
cache

11. DAGGER USAGE
Components Object
Find object
@Inject
Take all fields with annotation, look in the component and find the object by
type, and set the field.

12. DAGGER USAGE
@Inject Picasso Picasso;
@ Inject Preference preference onject
// in oncreate function
getComponent().inject(this)
Take all fields with annotation, look in the component and find the object by type, and set
the field.

13. ANNOTATIONS USED BY DAGGER 2
• @Module and @Provides
• @Inject
• @Components

14. MODULES & COMPONENTS
 Activities
 Fragmen
ts
 Views
 Objects
Network client
Shared
Preferences
Application
Network module
Storage module
Application
module
Applicati
on
compon
ent
.inject(
)

15. SCOPES
• @UserScope
• @Singleton
• @ActivityScope

16. CONSTRUCTOR INJECTION
@Provides
public StoreUserInfo
provideStorUserInfo(NetworkApi networkApi){
return new StoreUserInfo(networkApi);
}
public class MainActivity extends
AppCompatActivity {
@Inject
StoreUserInfo storeUserInfo;
@Override
protected void onCreate(Bundle
savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
((MyApplication)
getApplication()).getComponent()
.inject(this);
}

17. Contact:
 Paramvir Singh
 Paramvir.singh88@gmail.com