adapter.kt

package com.feresr.wallpapers.wallpapers

class WallpapersAdapter(private val context: Context, private val inflater: LayoutInflater) : BaseAdapter<Wallpaper>() {

    companion object {
        val TYPE_WALLPAPER: Int = 0
        val TYPE_LOADING: Int = 1
    }

    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, item: Wallpaper) {
        if (holder is WallpaperViewHolder) {
            GlideApp.with(context)
                    .load(item.thumbUrl)
                    .placeholder(ColorDrawable(Color.parseColor(item.color)))
                    .transition(DrawableTransitionOptions.withCrossFade())
                    .into(holder.wallpaperImageView)

            if (favourites.contains(item)) {
                holder.favouriteView.setImageResource(R.drawable.ic_heart_filled)
            } else {
                holder.favouriteView.setImageResource(R.drawable.ic_heart_outline)
            }

            listener?.apply {
                holder.itemView.setOnClickListener {
                    onWallpaperSelected(item)
                }

                holder.favouriteView.setOnClickListener {

                    if (favourites.contains(item)) {
                        if (onRemoveFromFavouriteSelected(item)) {
                            holder.favouriteView.setImageResource(R.drawable.ic_heart_out)
                            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
                                (holder.favouriteView.drawable as AnimatedVectorDrawable).start()
                            } else {
                                (holder.favouriteView.drawable as AnimatedVectorDrawableCompat).start()
                            }
                        }
                    } else {
                        holder.favouriteView.setImageResource(R.drawable.ic_heart_in)
                        onAddToFavouriteSelected(item)
                        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
                            (holder.favouriteView.drawable as AnimatedVectorDrawable).start()
                        } else {
                            (holder.favouriteView.drawable as AnimatedVectorDrawableCompat).start()
                        }
                    }

                }
            }
        }
    }

    private var listener: WallpaperClickedListener? = null
    var favourites: Set<Wallpaper> = HashSet()

    fun setWallpaperSelectedListener(listener: WallpaperClickedListener) {
        this.listener = listener
    }

    override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): RecyclerView.ViewHolder =
            when (viewType) {
                TYPE_WALLPAPER -> WallpaperViewHolder(inflater.inflate(R.layout.row_wallpaper, parent, false))
                TYPE_LOADING -> LoadingViewHolder(inflater.inflate(R.layout.progress_bar, parent, false))
                else -> throw IllegalStateException("Unknown viewType")
            }

    private class LoadingViewHolder(view: View) : RecyclerView.ViewHolder(view)

    class WallpaperViewHolder(view: View) : RecyclerView.ViewHolder(view) {
        val wallpaperImageView: ImageView = view.wallpaperImageView
        val favouriteView: ImageView = view.favouriteView
    }

    interface WallpaperClickedListener {
        fun onWallpaperSelected(wallpaper: Wallpaper)
        fun onWallpaperLongPressed(wallpaper: Wallpaper)
        fun onAddToFavouriteSelected(wallpaper: Wallpaper)

        /*
        * Return true if the heart favourite animation should be run, false otherwise
        * */
        fun onRemoveFromFavouriteSelected(wallpaper: Wallpaper): Boolean
    }
}



abstract class BaseWallpapersFragment : BaseFragment<Explore.Intent, Explore.ViewState>(), BaseAdapter.PagerListener, WallpapersAdapter.WallpaperClickedListener {

    private val NUMBER_OF_COLUMNS = 2
    private val wallpapersAdapter: WallpapersAdapter by lazy {
    //I use the applicationContext because this is a RetainedFragment
        WallpapersAdapter(activity.applicationContext, activity.applicationContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater)
    }