Android/kotlin/Dagger2

dagger2とは

Google製のDIライブラリ

サンプル

dagger2を使って、例として、年齢(age)を取得する方法

app/build.gradle

apply plugin: 'kotlin-kapt'

dependencies {
    def dagger_version = 2.27
    implementation "com.google.dagger:dagger:$dagger_version"
    annotationProcessor "com.google.dagger:dagger-compiler:$dagger_version"
    kapt "com.google.dagger:dagger-compiler:$dagger_version"
    kaptTest "com.google.dagger:dagger-compiler:$dagger_version"
}

MainActivity.kt

<pre>
package com.example.daggerapplication

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import javax.inject.Inject

class MainActivity : AppCompatActivity() {
    @Inject
    lateinit var viewModel: MainViewModel

    private val component = DaggerMainActivityComponent.builder()
            .viewModelModule(ViewModelModule())
            .repositoryModule(RepositoryModule())
            .build()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        component.inject(this)

        Log.i("MainActivity", "age=" + viewModel.age())
    }
}

MainActivityComponent.kt

package com.example.daggerapplication

import dagger.Component

@Component(modules = [ViewModelModule::class, RepositoryModule::class])
interface MainActivityComponent {
    fun inject(activity: MainActivity)
}

MainViewModel.kt

package com.example.daggerapplication

import javax.inject.Inject

class MainViewModel @Inject constructor(private val userRepository: IUserRepository) {
    fun age(): Int {
        return userRepository.age()
    }
}

RepositoryModule.kt

package com.example.daggerapplication

import dagger.Module
import dagger.Provides

@Module
class RepositoryModule {
    @Provides
    fun provideUserRepository(): IUserRepository {
        return UserRepository()
    }
}

UserRepository.kt

package com.example.daggerapplication

class UserRepository : IUserRepository {
    override fun age(): Int {
        return 12
    }
}

IUserRepository.kt

package com.example.daggerapplication

interface IUserRepository {
    fun age(): Int
}

ViewModelModule.kt

package com.example.daggerapplication

import dagger.Module
import dagger.Provides

@Module
class ViewModelModule {
    @Provides
    fun provideMainViewModel(userRepository: IUserRepository): MainViewModel {
        return MainViewModel(userRepository)
    }
}

参考

https://qiita.com/sudachi808/items/a05237e1294639ea41dd

https://qiita.com/iTakahiro/items/c9203f5ad886b7ddae2f