Building a High-Performance Android Wallpaper App with Kotlin & Retrofit

1. Setting Up Retrofit in Android Studio

Add the following dependencies in your app-level build.gradle.kts:

implementation("com.squareup.retrofit2:retrofit:2.9.0")
implementation("com.squareup.retrofit2:converter-gson:2.9.0")
implementation("io.coil-kt:coil:2.5.0")
implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3")

2. Kotlin Retrofit API Service

interface NexWallApiService {
    @GET("api/developer/v1/wallpapers")
    suspend fun getWallpapers(
        @Header("Authorization") token: String = "Bearer YOUR_API_KEY",
        @Header("Accept") accept: String = "application/json",
        @Query("page") page: Int = 1,
        @Query("per_page") perPage: Int = 30,
        @Query("category_id") categoryId: Int? = null
    ): Response<WallpaperResponse>
}

3. Jetpack Compose or XML Image Loading

Load the 4K wallpaper smoothly using Coil in Jetpack Compose:

AsyncImage(
    model = wallpaper.thumbnailUrl,
    contentDescription = "4K Wallpaper",
    contentScale = ContentScale.Crop,
    modifier = Modifier
        .fillMaxWidth()
        .aspectRatio(9f / 16f)
        .clip(RoundedCornerShape(14.dp))
)