dependency injection and dagger2 in android paramvir singh
TRANSCRIPT
Dependency
injectionAND DAGGER2 FRAMEWORK IN ANDROID
WHAT IS DEPENDENCY?
INJECTION
Push dependency from outside into the class.
• Fetch dependency
• Receive dependency
DI
Ask third party to create object, instead of create dependencies
yourself.
WHY NEED DI
Decouple classes construction from construction of your
dependency.
DEPENDENCY INVERSION PRINCIPLE
Class Dependency
Interface
Implementation
Dependen
cy
DI CONTAINER
Create and map dependency
DI LIBRARY FOR ANDROID
• Dagger 2
Dagger 2
Dagger 2 analyzes dependencies for you and generates code to
help wire them together.
WITHOUT DAGGER 2
Activities
Fragments
Views
Objects
API interface
(Retrofit)
Image Loader
(Picasso)
Shared
Preference
Network client
Image disk
cache
DAGGER USAGE
Components ObjectFind object
@Inject
Take all fields with annotation, look in the component and find the object by
type, and set the field.
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.
ANNOTATIONS USED BY DAGGER 2
• @Module and @Provides
• @Inject
• @Components
MODULES & COMPONENTS
Activities
Fragmen
ts
Views
Objects
Network client
Shared
Preferences
Application
Network module
Storage module
Application
module
Applicati
on
compon
ent
.inject(
)
SCOPES
• @UserScope
• @Singleton
• @ActivityScope
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);
}
