Examples

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Before you get started with the examples, check out PART 1 and PART 2

Install Hilt on Application

Add dependencies
Annotate YouApplicationClass with @HiltAndroidApp
Code:

@HiltAndroidApp
MyApplication : Application()

To Provide Dependency to `Activity`/`Fragment`

To @Inject any object to Activity or Fragment, we need to annotate Activity or Fragment with @AnroidEntryPoint
Code:

@AndroidEntryPoint
SampleActivity : BaseActivity(){
      @Inject
      lateinit var somethingObject : SomethingObject
}

To Provide Dependency to `ViewModel`

To @Inject any object to ViewModel, we need to annotate ViewModel with @HiltViewModel and @Inject the constructor.
Code:

@HiltViewModel
SomethingViewModel @Inject constructor() : BaseViewModel(){
      @Inject
      lateinit var somethingObject : SomethingObject
}

`ViewModel` Constructor Injection

To @Inject objects to ViewModel, we need to annotate ViewModel with @HiltViewModel and @Inject the constructor.
Code:

@HiltViewModel
SomethingViewModel @Inject constructor
(private val somethingObject : SomethingObject) 
: BaseViewModel(){...}

Provide Foreground Activity `Context` to any Injectable Class

To provide ActivityContext to any Injectable Class, @Inject class constructor and annotate context with @ActivityContext and register in ActivityComponent module to provide the Context.
Code:

// Lets see how to inject a custom dialog object to an activity or fragment

// First, create a CustomDialog class and inject the constructor with Context object
class CustomDialog @Inject constructor(@ActivityContext private val context : Context){....}

// Second, Register the CustomDialog to any ActivityComponent module
@Module
@InstallIn(ActivityComponent::class)
object ActivityModule{
    @Provide
    fun provideCustomDialog(@ActivityContext context : Context) : CustomDialog = CustomDialog(context)
}

// Third, Inject the CustomDialog to any activity or fragment
@AndroidEntryPoint
class Activity/Fragment : BaseActivity/BaseFragment{
    @Inject
    lateinit var customDialog : CustomDialog
}

How to Inject `Interface` or `Abstract Class`

To provide an instance of Interface or Abstract Class to any dependent object, we can't directly inject any interface or abstract class becuase there is no way to initialize interface or abstract class. So, we have to provide an Implementation of the interface or abstract class.
Code:

// Define an interface
interface SomethingObject{
    fun doSomething()
}

// Define the implementation
class SomethingObjectImpl @Inject constructor() : SomethingObject{
    @override
    fun doSomething(){...}
}

// Register the SomeObject to any *Component module
@Module
@InstallIn(SingletonComponent/ActivityComponent/ViewModelComponent::class)
object SomethingModule{    
    @Provide
    fun provideSomethingObject() : SomethingObject = SomethingObjectImpl()
}

That's it for this series. Happy Coding...

Dependency Injection (Android): Implementation with Examples (Hilt) [PART 3]

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Android Application Development

Dependency Injection (Android): Implementation (Hilt) [PART 2]

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Examples

Install Hilt on Application

To Provide Dependency to `Activity`/`Fragment`

To Provide Dependency to `ViewModel`

`ViewModel` Constructor Injection

Provide Foreground Activity `Context` to any Injectable Class

How to Inject `Interface` or `Abstract Class`

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Comments

Android Application Development

Dependency Injection (Android): Implementation (Hilt) [PART 2]

More from this blog

Examples

Install Hilt on Application

To Provide Dependency to Activity/Fragment

To Provide Dependency to ViewModel

ViewModel Constructor Injection

Provide Foreground Activity Context to any Injectable Class

How to Inject Interface or Abstract Class

To Provide Dependency to `Activity`/`Fragment`

To Provide Dependency to `ViewModel`

`ViewModel` Constructor Injection

Provide Foreground Activity `Context` to any Injectable Class

How to Inject `Interface` or `Abstract Class`