Halo. Suatu hari saya mengalami masalah dalam mengimplementasikan pilihan beberapa item di RecyclerView menggunakan dataBinding.
Memulai
Pertama, mari tulis adaptor dasar yang mendukung dataBinding.
/**
* data binding'.
* @param layoutRes id layout',
* @param lifecycleOwner lifecycle owner , recycler view
* @param itemBindingId id layout',
* @param onClick ,
*/
class RecyclerViewAdapter<Item : IRecyclerViewItem>(
@LayoutRes private val layoutRes: Int,
private val lifecycleOwner: LifecycleOwner,
private val itemBindingId: Int? = null,
private val onClick: ((Item) -> Unit)? = null
) : RecyclerView.Adapter<RecyclerViewAdapter<Item>.ViewHolder>() {
private val items = mutableListOf<Item>()
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val inflater = LayoutInflater.from(parent.context)
// ViewDataBinding layoutRes
val binding = DataBindingUtil.inflate<ViewDataBinding>(inflater, layoutRes, parent, false)
return ViewHolder(binding)
}
override fun getItemCount(): Int = items.size
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
// onBind
val item = items[position]
holder.onBind(item)
}
/**
*
*
* @param newItems
*/
fun setItems(newItems: List<Item>) {
val diffUtilCallback = DiffUtilCallback(newItems)
val diffResult = DiffUtil.calculateDiff(diffUtilCallback)
items.apply {
clear()
addAll(newItems)
}
diffResult.dispatchUpdatesTo(this)
}
// DataBinding'
inner class ViewHolder(
private val binding: ViewDataBinding
) : RecyclerView.ViewHolder(binding.root) {
fun onBind(item: Item) {
binding.apply {
//
setVariable(itemBindingId ?: BR.item, item)
root.setOnClickListener { onClick?.invoke(item) }
lifecycleOwner = this@RecyclerViewAdapter.lifecycleOwner
}
}
}
private inner class DiffUtilCallback(private val newItems: List<Item>) : DiffUtil.Callback() {
override fun getOldListSize(): Int = itemCount
override fun getNewListSize(): Int = newItems.size
override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
return newItems[newItemPosition].id == items[oldItemPosition].id
}
override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
return newItems[newItemPosition] == items[oldItemPosition]
}
}
}
Juga, agar DiffUtil berfungsi, saya membuat antarmuka yang menunjukkan bahwa elemen tersebut memiliki bidang yang unik
/**
* ui , RecyclerViewAdapter.
* @property id
*/
interface IRecyclerViewItem {
val id: Int
}
Hingga saat ini, adaptor ini mampu menyelesaikan hampir semua tugas dengan daftar. Bergantung pada proyeknya, onClick dapat diganti dengan onBind: (binding: ViewDataBinding) -> Unit, sehingga Anda dapat menyesuaikan elemen individual item.
Pembantu seleksi
, SelectionHelper, dataBinding' .
, , , .
, , :
class SelectionHelper<T : IRecyclerViewItem> : ISelectionHelper<T>() {
//
private val selectedItems = mutableMapOf<Int, T>()
// , - , -
override fun handleItem(item: T) {
if (selectedItems[item.id] == null) {
selectedItems[item.id] = item
} else {
selectedItems.remove(item.id)
}
// dataBining, ui)
notifyChange()
}
override fun isSelected(id: Int): Boolean = selectedItems.containsKey(id)
override fun getSelectedItems(): List<T> = selectedItems.values.toList()
override fun getSelectedItemsSize(): Int = selectedItems.size
}
// BaseObservable, , dataBinding
//
abstract class ISelectionHelper<T : IRecyclerViewItem> : BaseObservable() {
abstract fun handleItem(item: T)
abstract fun isSelected(id: Int): Boolean
abstract fun getSelectedItems(): List<T>
abstract fun getSelectedItemsSize(): Int
}
:
viewModel selectionHelper.getSelectedItems, .
DataBinding, - adapter
, onBind
:
viewModel/presenter ,
xml
- ,
adadpter
class RecyclerViewAdapter<Item : IRecyclerViewItem>(
@LayoutRes private val layoutRes: Int,
private val lifecycleOwner: LifecycleOwner,
private val itemBindingId: Int? = null,
// , ,
private val selectionHelper: ISelectionHelper<Item>? = null,
private val onClick: ((Item) -> Unit)? = null
) : RecyclerView.Adapter<RecyclerViewAdapter<Item>.ViewHolder>() {
...
inner class ViewHolder(
private val binding: ViewDataBinding
) : RecyclerView.ViewHolder(binding.root) {
fun onBind(item: Item) {
binding.apply {
//
setVariable(itemBindingId ?: BR.item, item)
selectionHelper?.let { setVariable(BR.selectionHelper, it) }
root.setOnClickListener {
//
selectionHelper?.handleItem(item)
onClick?.invoke(item)
}
lifecycleOwner = this@RecyclerViewAdapter.lifecycleOwner
}
}
}
}
/ , , onBind, - .
class RecyclerViewAdapter<Item : IRecyclerViewItem>(
@LayoutRes private val layoutRes: Int,
private val lifecycleOwner: LifecycleOwner,
private val itemBindingId: Int? = null,
private val selectionHelper: ISelectionHelper<Item>? = null,
private val onClick: ((Item) -> Unit)? = null
) : RecyclerView.Adapter<RecyclerViewAdapter<Item>.ViewHolder>() {
private val items = mutableListOf<Item>()
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val inflater = LayoutInflater.from(parent.context)
val binding = DataBindingUtil.inflate<ViewDataBinding>(inflater, layoutRes, parent, false)
return ViewHolder(binding)
}
override fun getItemCount(): Int = items.size
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val item = items[position]
holder.onBind(item)
}
/**
*
*
* @param newItems
*/
fun setItems(newItems: List<Item>) {
val diffUtilCallback = DiffUtilCallback(newItems)
val diffResult = DiffUtil.calculateDiff(diffUtilCallback)
items.apply {
clear()
addAll(newItems)
}
diffResult.dispatchUpdatesTo(this)
}
inner class ViewHolder(
private val binding: ViewDataBinding
) : RecyclerView.ViewHolder(binding.root) {
fun onBind(item: Item) {
binding.apply {
//
setVariable(itemBindingId ?: BR.item, item)
selectionHelper?.let { setVariable(BR.selectionHelper, it) }
root.setOnClickListener {
//
selectionHelper?.handleItem(item)
onClick?.invoke(item)
}
lifecycleOwner = this@RecyclerViewAdapter.lifecycleOwner
}
}
}
private inner class DiffUtilCallback(private val newItems: List<Item>) : DiffUtil.Callback() {
override fun getOldListSize(): Int = itemCount
override fun getNewListSize(): Int = newItems.size
override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
return newItems[newItemPosition].id == items[oldItemPosition].id
}
override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
return newItems[newItemPosition] == items[oldItemPosition]
}
}
}
, xml , selectionHelper xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<data>
<variable
name="item"
type="ImageItemUi" />
<!-- ) -->
<variable
name="selectionHelper"
type="dev.syncended.ctime.utils.ui.ISelectionHelper<ImageItemUi>" />
<import type="dev.syncended.ctime.models.ui.ImageItemUi" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<ImageView
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_margin="@dimen/ui_spacing_normal"
android:padding="@dimen/1dp"
android:scaleType="centerCrop"
app:file="@{item.file}"
app:item_id="@{item.id}"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintDimensionRatio="1:1"
app:layout_constraintTop_toTopOf="parent"
app:selection_helper="@{selectionHelper}"
tools:ignore="ContentDescription" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
padding = 1dp, , , .
bindingAdapter selectionHelper
// selectionHelper', id
@BindingAdapter("selection_helper", "item_id", requireAll = true)
fun <T : IRecyclerViewItem> handleSelection(
view: View,
selectionHelper: ISelectionHelper<T>,
itemId: Int
) {
//
val isSelected = selectionHelper.isSelected(itemId)
//
val color = if (isSelected) {
R.color.color_primary
} else {
android.R.color.transparent
}
view.setBackgroundColor(ContextCompat.getColor(view.context, color))
}
, background.
:
:
Hasilnya, kami mendapat alat yang cukup sederhana untuk memilih item daftar. Jika Anda beralih dari pemilihan biasa dengan bingkai, Anda dapat mengubah status, katakanlah, kotak centang, bergantung pada apakah elemen dipilih atau tidak.
android:checked=@{selectionHelper.isSelected(item.id)}
Dengan analogi, Anda dapat membuat banyak variasi berbeda menggunakan helper ini.
Terima kasih sudah membaca, ini artikel pertama saya, jadi jangan menilai dengan tegas, tapi juga pelihara kucingnya.
