Kotlin Dependency Injection With Dagger2

Prepare

1. Install Android Studio version 3.0.1 or more
2. Create new android project and check on "Include Kotlin support"

I. Compile library

• build.gradle module app

    apply plugin: "kotlin-kapt"

    def dagger = 2.24
    def daggerCompiler = 2.24

    kapt {
        generateStubs = true
    }

    dependencies {
        ...

        implementation "com.google.dagger:dagger:$dagger"
        implementation "com.google.dagger:dagger-android:$dagger"
        kapt "com.google.dagger:dagger-compiler:$daggerCompiler"
        kapt "com.google.dagger:dagger-android-processor:$daggerCompiler"
    }

II. Config

1. Create folder and files folow structure

    PACKAGE
    |-- domain
        |-- home
            |-- HomeActivity.kt
            |-- HomeComponent.kt
        |-- second
            |-- SecondActivity.kt
            |-- SecondComponent.kt
    |-- infrastructures
        |-- model
            |-- Person.kt
        |-- module
            |-- ActivityModule.kt
            |-- ApplicationComponent.kt
            |-- ApplicationModule.kt
        |-- scope
            |-- ActivityScope.kt
            |-- ApplicationScope.kt
    |-- MainApplication.kt

2. Create files and content flow as

• ApplicationScope.kt
• ActivityScope.kt
• ApplicationModule.kt
• ApplicationComponent.kt
• ActivityModule.kt
• Person.kt
• HomeActivity.kt
• HomeComponent.kt
• SecondActivity.kt
• SecondComponent.kt
• MainApplication.kt
• AndroidManifest.xml

    <application
        ...
        android:name=".MainApplication">
        
        ...
    </application>

• activity_home.xml
• activity_second.xml

III. Use

• In ApplicationModule, create Person for app

    @Module
    class ApplicationModule(val app: Application) {
        ...

        @Provides
        @ApplicationScope
        fun providePerson(): Person {
            return Person("Alice", 30)
        }
    }

• In ApplicationComponent provide resources created by ApplicationModule

    @ApplicationScope
    @Component(modules = arrayOf(ApplicationModule::class))
    interface ApplicationComponent {
        fun person(): Person
    }

• In each activity will inject to use without create new Person

    @Inject lateinit var person: Person

HomeActivity:

SecondActivity: