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getChangePayload
in DiffUtil
potatotips #70
2020/07/10 rmakiyama
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ɹɹࣗݾհ
•ࢁྎ
•Radiotalkגࣜձࣾ
•AndroidΤϯδχΞ
• @_rmakiyama
• rmakiyama
ref. https:"//github.com/rmakiyama/recyclerview-playground
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Ϧετͷࠩߋ৽
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Androidʹ͓͚ΔϦετUIͷදࣔ
• RecyclerViewΛϨΠΞτʹՃ
• LayoutManagerΛઃఆ͠ஔํ๏Λࢦఆ
• RecyclerView.AdapterΛηοτ
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RecyclerViewͷߋ৽
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RecyclerView.AdapterͰͷϦετߋ৽
• notifyDataSetChanged
• notifyItemChanged
• notifyItemInserted
• notifyItemMoved
• bla bla bla…
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DiffUtil
• ̎ͭͷϦετͷࠩΛޮΑ͘ܭࢉ
• ܭࢉ݁Ռ͔ΒRecyclerViewΛ͍͍ײ͡ʹߋ৽
• దͳnotifyϝιουΛݺΜͰ͘ΕΔ
• దͳΞχϝʔγϣϯ͕ݺΕΔ
• ίʔϧόοΫΛ࣮ͯ͠͏
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DiffUtil.Callback
public abstract static class Callback {
public abstract int getOldListSize();
public abstract int getNewListSize();
public abstract boolean areItemsTheSame(int oldItemPosition, int newItemPosition);
public abstract boolean areContentsTheSame(int oldItemPosition, int newItemPosition);
public Object getChangePayload(int oldItemPosition, int newItemPosition) {
return null;
}
}
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DiffUtil.ItemCallback
public abstract static class ItemCallback {
public abstract boolean areItemsTheSame(@NonNull T oldItem, @NonNull T newItem);
public abstract boolean areContentsTheSame(@NonNull T oldItem, @NonNull T newItem);
public Object getChangePayload(@NonNull T oldItem, @NonNull T newItem) {
return null;
}
}
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DiffUtil.ItemCallback
• areItemsTheSame
• ΞΠςϜ͕ಉ͔͡ఆ݁͠ՌΛฦ͢
• areContentsTheSame
• ΞΠςϜͷத͕ಉ͔͡ఆ݁͠ՌΛฦ͢
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areItemsTheSame
• ΞΠςϜ͕ಉ͔͡ఆ
• ҰҙͳࣝผࢠͰൺֱ͢Δͱྑ͍
• ྫͰUserΛஔ͖͍͑ͯΔ
• notifyItemRangeRemoved
• notifyItemRangeInserted
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areContentsTheSame
• ΞΠςϜͷத͕ಉ͔͡ఆ
• areItemsTheSame͕trueͷͱ͖ධՁ
• ྫͰImageUrl / isFavoriteΛมߋ
• notifyItemRangeChanged
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DiffUtil.ItemCallback
public abstract static class ItemCallback {
public abstract boolean areItemsTheSame(@NonNull T oldItem, @NonNull T newItem);
public abstract boolean areContentsTheSame(@NonNull T oldItem, @NonNull T newItem);
public Object getChangePayload(@NonNull T oldItem, @NonNull T newItem) {
return null;
}
}
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getChangePayload
• areItemsTheSame͕true͔ͭ
areContentsTheSame͕falseͰݺΕΔ
• มߋʹؔ͢ΔϖΠϩʔυΛΦϒδΣΫτͰฦͤΔ
• ࡉ͔͍ߋ৽ͷ੍ޚ͕Մೳ
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ྫʣUserDiff.kt
object UserDiff : DiffUtil.ItemCallback() {
override fun areItemsTheSame(oldItem: User, newItem: User): Boolean {
return oldItem.id "== newItem.id
}
override fun areContentsTheSame(oldItem: User, newItem: User): Boolean {
return oldItem "== newItem
}
…
}
data class User(
val id: String,
val imageUrl: String,
val isFavorite: Boolean
)
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ྫʣUserDiff.kt
object UserDiff : DiffUtil.ItemCallback() {
…
override fun getChangePayload(oldItem: User, newItem: User): Any? {
return when {
oldItem.imageUrl "!= newItem.imageUrl "-> Payload.ImageUrl(newItem.imageUrl)
oldItem.isFavorite "!= newItem.isFavorite "-> Payload.IsFavorite(newItem.isFavorite)
else "-> null
}
}
sealed class Payload {
data class ImageUrl(val value: String) : Payload()
data class IsFavorite(val value: Boolean) : Payload()
}
}
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ListAdapterΛͬͨ߹
class UserListAdapter() : ListAdapter(UserDiff) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): UserViewHolder {
…
return UserViewHolder(…)
}
override fun onBindViewHolder(holder: UserViewHolder, position: Int) {
holder.bind(getItem(position))
}
…
}
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ListAdapterΛͬͨ߹
class UserListAdapter() : ListAdapter(UserDiff) {
…
override fun onBindViewHolder(holder: UserViewHolder, position: Int, payloads: MutableList) {
if (payloads.isEmpty()) {
onBindViewHolder(holder, position)
} else {
payloads.distinct().forEach { payload "->
when (payload) {
is UserDiff.Payload.ImageUrl "-> holder.updateImageUrl(payload.value)
is UserDiff.Payload.IsFavorite "-> holder.updateFavorite(payload.value)
}
}
}
}
}
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ListAdapterΛͬͨ߹
class UserViewHolder(binding: ItemDummyBinding) : RecyclerView.ViewHolder(binding.root) {
fun bind(user: User) {
"// ViewʹUserใΛදࣔ
val binding = ItemDummyBinding.bind(itemView)
binding.uuid.text = user.id
loadImage(user.imageUrl)
setImageRes(user.isFavorite)
}
fun updateImageUrl(imageUrl: String) = loadImage(imageUrl)
fun updateFavorite(isFavorite: Boolean) = setImageRes(isFavorite)
…
}
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w BGUFS
isFavoriteมߋͰը૾͕ͪΒ͔ͭͳ͍
• before
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͓·͚ɿGroupieΛར༻͍ͯ͠Δ߹
• Item#isSameAs
• areItemsTheSame
• Item#hasSameContentAs
• areContentsTheSame
• Item#getChangePayload
• getChangePayload
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·ͱΊ
• DiffUtilΛ͏͜ͱͰࠩߋ৽ָ͕ʹͳΔ
• getChangePayloadΛ͏ͱࡉ੍͔͘ޚՄೳ
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Appendix
• https:"//developer.android.com/guide/topics/ui/layout/recyclerview
• https:"//developer.android.com/reference/androidx/recyclerview/widget/DiffUtil
• https:"//medium.com/tech-insider/diffutil-handling-recyclerview-smartly-
ac3401d22903
• https:"//satoshun.github.io/2019/11/groupie-diffutil/
• https:"//github.com/DroidKaigi/conference-app-2020/pull/331
• https:"//github.com/rmakiyama/recyclerview-playground