How to create and configure Dagger Hilt in an Android application?

1. Adding dependencies in build.gradle (Project):

// project-level build.gradle
buildscript {
    ext {
        hilt_version = '2.48' // Use the latest Hilt version
    }
    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath "com.google.dagger:hilt-android-gradle-plugin:$hilt_version"
        // ... other dependencies
    }
}

allprojects {
    repositories {
        google()
        mavenCentral()
        // ... other repositories
    }
}

2. Adding dependencies in build.gradle (Module):

// app-level build.gradle
plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id 'kotlin-kapt' // For Kapt code generation
    id 'dagger.hilt.android.plugin'
}

android {
    // ...
}

dependencies {
    implementation "com.google.dagger:hilt-android:$hilt_version"
    kapt "com.google.dagger:hilt-compiler:$hilt_version"
    kapt "androidx.hilt:hilt-compiler:1.0.0" // Optional, for Android-specific Hilt extensions
    // ... other dependencies
}

3. Creating the main application class with @HiltAndroidApp annotation:

// MyAndroidApp.kt
import android.app.Application
import dagger.hilt.android.HiltAndroidApp

@HiltAndroidApp
class MyAndroidApp : Application() {
    // Additional initialization if needed
}

4. Registering the created class in AndroidManifest.xml:

<!-- AndroidManifest.xml -->
<application
    android:name=".MyAndroidApp"
    ...>
    <!-- ... -->
</application>

5. Annotating Android components (Activity, Fragment, Service, etc.) with @AndroidEntryPoint:

// MyActivity.kt
import androidx.appcompat.app.AppCompatActivity
import dagger.hilt.android.AndroidEntryPoint

@AndroidEntryPoint
class MyActivity : AppCompatActivity() {
    // ...
}

Now, Hilt is ready to be used for dependency injection in annotated classes. You can then create modules (@Module), provide dependencies (@Provides or @Binds) within modules, and inject them into components using @Inject.

Example of a module:

// NetworkModule.kt
import dagger.Module
import dagger.Provides
import dagger.hilt.InstallIn
import dagger.hilt.components.SingletonComponent
import retrofit2.Retrofit
import javax.inject.Singleton

@Module
@InstallIn(SingletonComponent::class) // Install module in application scope
object NetworkModule {

    @Provides
    @Singleton
    fun provideRetrofit(): Retrofit {
        return Retrofit.Builder()
            // ... Retrofit configuration
            .build()
    }

    // Other dependency provisions
}

Example of dependency injection:

// MyActivity.kt
import androidx.appcompat.app.AppCompatActivity
import dagger.hilt.android.AndroidEntryPoint
import retrofit2.Retrofit
import javax.inject.Inject

@AndroidEntryPoint
class MyActivity : AppCompatActivity() {

    @Inject
    lateinit var retrofit: Retrofit // Inject Retrofit dependency

    // ... use retrofit
}