Adapter for switching items

FavoriteItemsListAdapter.kt

class FavoriteItemsListAdapter(
    private val activity: Activity,
    private val listener: (section: FavoriteSection) -> Unit
) : ListAdapter<FavoriteItem, FavoriteItemsListAdapter.FavoriteViewHolder>(DiffCallback()) {

    private var recyclerView: RecyclerView? = null

    override fun onAttachedToRecyclerView(recyclerView: RecyclerView) {
        super.onAttachedToRecyclerView(recyclerView)
        this.recyclerView = recyclerView
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): FavoriteViewHolder {
        val binding = ItemFavoriteBinding.inflate(parent.getInflater(), parent, false)
        if (itemCount == 2) binding.root.setTwoItemsWidth()
        return FavoriteViewHolder(binding)
    }

    override fun onBindViewHolder(holder: FavoriteViewHolder, position: Int) {
        super.onBindViewHolder(holder, position, emptyList())
    }

    override fun onBindViewHolder(
        holder: FavoriteViewHolder,
        position: Int,
        payloads: MutableList<Any>
    ) {
        val payload = payloads.firstOrNull() as? FavoritePayload
        if (payload == null) {
            holder.bind(currentList[position])
        } else {
            holder.updateSelection(payload.backgroundRes, payload.selected)
        }
    }

    override fun getItemCount() = currentList.size

    private fun ViewGroup.setTwoItemsWidth() {
        if (activity.isTablet) {
            val width = resources.getDimensionPixelSize(R.dimen.top_lists_selectors_container_width)
            layoutParams.width = width / 2
        } else {
            val screenWidth = activity.getScreenParams().widthPixels
            val padding = recyclerView?.paddingStart ?: 0
            layoutParams.width = screenWidth / 2 - padding
        }
    }

    inner class FavoriteViewHolder(
        private val binding: ItemFavoriteBinding,
    ) : RecyclerView.ViewHolder(binding.root) {

        fun bind(item: FavoriteItem) {
            with(binding) {
                updateSelection(item.backgroundRes, item.selected)
                tvTitle.text = item.type.title.string()
                root.setOnClickListener { listener.invoke(item.type) }
            }
        }

        fun updateSelection(@DrawableRes backgroundRes: Int, selected: Boolean) {
            with(binding) {
                selector.visibleOrGone(selected)
                root.setBackgroundResource(backgroundRes)
            }
        }
    }

    private class DiffCallback : DiffUtil.ItemCallback<FavoriteItem>() {

        override fun areItemsTheSame(oldItem: FavoriteItem, newItem: FavoriteItem) =
            oldItem.type == newItem.type

        override fun areContentsTheSame(oldItem: FavoriteItem, newItem: FavoriteItem) =
            oldItem == newItem

        override fun getChangePayload(oldItem: FavoriteItem, newItem: FavoriteItem): Any? {
            return when {
                oldItem.selected != newItem.selected -> {
                    FavoritePayload(newItem.backgroundRes, newItem.selected)
                }
                else -> null
            }
        }
    }

    private data class FavoritePayload(
        @DrawableRes val backgroundRes: Int,
        val selected: Boolean
    )
}


class FavoriteItemsLayoutManager(
    context: Context
) : LinearLayoutManager(context, RecyclerView.HORIZONTAL, false) {

    private val smoothScroller: RecyclerView.SmoothScroller by lazy {
        CenterSmoothScroller(context)
    }

    override fun smoothScrollToPosition(
        recyclerView: RecyclerView,
        state: RecyclerView.State,
        position: Int
    ) {
        smoothScroller.targetPosition = position
        startSmoothScroll(smoothScroller)
    }

    private class CenterSmoothScroller(context: Context) : LinearSmoothScroller(context) {

        override fun calculateDtToFit(
            viewStart: Int,
            viewEnd: Int,
            boxStart: Int,
            boxEnd: Int,
            snapPreference: Int
        ): Int {
            return boxStart + (boxEnd - boxStart) / 2 - (viewStart + (viewEnd - viewStart) / 2)
        }

        override fun calculateSpeedPerPixel(displayMetrics: DisplayMetrics): Float {
            return MILLISECONDS_PER_INCH / displayMetrics.densityDpi
        }

        override fun calculateTimeForScrolling(dx: Int): Int {
            return super.calculateTimeForScrolling(dx)
                .coerceAtLeast(MIN_SCROLLING_TIME_MS)
        }
    }

    companion object {
        private const val MILLISECONDS_PER_INCH = 100f // default is 25f (bigger = slower)
        private const val MIN_SCROLLING_TIME_MS = 200
    }
}


// GetFavoriteItemsUseCase.kt
class GetFavoriteItemsUseCase(
    coroutineDispatcher: CoroutineDispatcher,
    private val getUserUseCase: GetUserUseCase,
) : CoroutineUseCase<GetFavoriteItemsUseCase.Params, List<FavoriteItem>>(coroutineDispatcher) {

    override suspend fun execute(parameters: Params): List<FavoriteItem> {
        val (sectionId, isUserUSM) = parameters

        val user = getUserUseCase(Unit).successOrThrow()
        val hasFavorites = user.user.hasA360Favorites

        val currentSection = when {
            sectionId != -1 -> sectionId
            isUserUSM && !hasFavorites -> FavoriteSection.TOP_LISTS.id
            else -> FavoriteSection.FAVORITES.id
        }

        val sections = FavoriteSection.values().toMutableList()
        if (!isUserUSM) sections.remove(FavoriteSection.TOP_LISTS)

        return sections.mapIndexed { index, favoriteSection ->
            FavoriteItem(
                type = favoriteSection,
                backgroundRes = when (index) {
                    0 -> R.drawable.background_favorite_start
                    sections.lastIndex -> R.drawable.background_favorite_end
                    else -> R.drawable.background_favorite_default
                },
                selected = favoriteSection.id == currentSection,
            )
        }
    }

    data class Params(
        val sectionId: Int,
        val isUserUSM: Boolean,
    )
}

// FavoriteItem.kt
data class FavoriteItem(
    val type: FavoriteSection,

    @DrawableRes val backgroundRes: Int = R.drawable.background_favorite_default,

    val selected: Boolean = false,
)

// 



// item_favorite.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="wrap_content"
    android:layout_height="@dimen/favorite_item_height">

    <View
        android:id="@+id/selector"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_margin="@dimen/margin_2"
        android:background="@drawable/background_favorite_selected"
        android:elevation="2dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/tvTitle"
        style="@style/TextAppearance.TextSemiBold"
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:layout_margin="@dimen/margin_2"
        android:elevation="2dp"
        android:gravity="center"
        android:includeFontPadding="false"
        android:paddingHorizontal="@dimen/padding_16"
        android:textColor="@color/black"
        android:textSize="@dimen/textSize_14"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>
  
  
  
// Selected
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="@color/colorWhite" />
    <corners android:radius="@dimen/selector_shapeRadius" />
</shape>
  
// Default
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="@color/bgFavoriteItem" />
</shape>
  
// End
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="@color/bgFavoriteItem" />
    <corners
        android:bottomRightRadius="@dimen/selector_shapeRadius"
        android:topRightRadius="@dimen/selector_shapeRadius" />
</shape>

// Start
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="@color/bgFavoriteItem" />
    <corners
        android:bottomLeftRadius="@dimen/selector_shapeRadius"
        android:topLeftRadius="@dimen/selector_shapeRadius" />
</shape>