Created
September 26, 2020 17:29
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A DSL for creating `ListAdapter`s
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import android.view.LayoutInflater | |
import android.view.View | |
import android.view.ViewGroup | |
import androidx.annotation.LayoutRes | |
import androidx.recyclerview.widget.DiffUtil | |
import androidx.recyclerview.widget.ListAdapter | |
import androidx.recyclerview.widget.RecyclerView | |
fun <T, VH : ListAdapterBuilder.ViewHolder<T>> createListAdapter( | |
init: ListAdapterBuilder<T, VH>.() -> Unit | |
): ListAdapter<T, VH> = ListAdapterBuilder(init).build() | |
class ListAdapterBuilder<T, VH : ListAdapterBuilder.ViewHolder<T>>() { | |
constructor(init: ListAdapterBuilder<T, VH>.() -> Unit) : this() { | |
init() | |
} | |
@LayoutRes private var layoutRes: Int? = null | |
private var areItemsEqualByReference: ((T, T) -> Boolean)? = null | |
private var areItemsEqualByContent: ((T, T) -> Boolean)? = null | |
private var viewHolderCreation: ((View, Int) -> VH)? = null | |
private var itemViewType: (Int, Int) -> Int = { _, _ -> layoutRes ?: 1 } | |
fun layout(init: () -> Int) { layoutRes = init() } | |
fun compareItemsByReference(f: (T, T) -> Boolean) { | |
areItemsEqualByReference = f | |
} | |
fun compareItemsByContent(f: (T, T) -> Boolean) { | |
areItemsEqualByContent = f | |
} | |
fun viewHolderCreation(f: (View, Int) -> VH) { | |
viewHolderCreation = f | |
} | |
fun viewTypeByPosition(f: (Int, Int) -> Int) { | |
itemViewType = f | |
} | |
fun build(): ListAdapter<T, VH> { | |
val layout = requireNotNull(layoutRes) | |
val byReference = requireNotNull(areItemsEqualByReference) | |
val byContent = requireNotNull(areItemsEqualByContent) | |
val createViewHolder = requireNotNull(viewHolderCreation) | |
val diffCalculator = object : DiffUtil.ItemCallback<T>() { | |
override fun areItemsTheSame(oldItem: T, newItem: T): Boolean = | |
byReference(oldItem, newItem) | |
override fun areContentsTheSame(oldItem: T, newItem: T): Boolean = | |
byContent(oldItem, newItem) | |
} | |
return object : ListAdapter<T, VH>(diffCalculator) { | |
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): VH = | |
LayoutInflater.from(parent.context) | |
.inflate(layout, parent, false) | |
.run { createViewHolder(this, viewType) } | |
override fun onBindViewHolder(holder: VH, position: Int) { | |
holder.bind(getItem(position)) | |
} | |
override fun getItemViewType(position: Int): Int { | |
return itemViewType(position, itemCount) | |
} | |
} | |
} | |
abstract class ViewHolder<T>(itemView: View) : RecyclerView.ViewHolder(itemView) { | |
abstract fun bind(item: T) | |
} | |
} |
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