使用 ItemTouchHelper 拖动项目时 RecyclerView 滚动到顶部
RecyclerView scrolls to top when dragging item with ItemTouchHelper
我有一个奇怪的错误,每当我开始在其中拖动项目时,我的 RecyclerView
就会滚动回到顶部位置。如果有任何区别,它在 ViewPager
内。您可以在附加的 .gif 中看到行为。
编辑:
当 notifyItemMoved
被调用时,RecyclerView
视图似乎滚动到顶部,并且它滚动到第一个视图至少部分显示在屏幕上。
查看
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/accounts_recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbarStyle="outsideOverlay"
android:scrollbars="none"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
tools:listitem="@layout/view_account_list_item" />
适配器
class AccountListAdapter(
private val onAccountClickListener: OnAccountClickListener) :
ListAdapter<Account, AccountListAdapter.ViewHolder>(
AccountDiffCallback()
) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val inflater = LayoutInflater.from(parent.context)
return ViewHolder(
inflater.inflate(
R.layout.view_account_list_item,
parent,
false
)
)
}
override fun getItemId(position: Int): Long {
return getItem(position).accountId.toLong()
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.bind(getItem(position), onAccountClickListener)
}
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView), OnItemDragged {
fun bind(account: Account, onAccountClickListener: OnAccountClickListener) {
itemView.account_name.text = account.name
itemView.setOnClickListener {
onAccountClickListener.onAccountClick(account)
}
}
override fun onItemSelected() {
itemView.setBackgroundColor(
ContextCompat.getColor(
itemView.context,
R.color.background_contrast
)
)
}
override fun onItemClear() {
itemView.setBackgroundColor(
ContextCompat.getColor(
itemView.context,
R.color.background
)
)
}
}
class AccountDiffCallback : DiffUtil.ItemCallback<Account>() {
override fun areItemsTheSame(oldItem: Account, newItem: Account): Boolean {
return oldItem.accountId == newItem.accountId
}
override fun areContentsTheSame(oldItem: Account, newItem: Account): Boolean {
return (oldItem.balance == newItem.balance
&& oldItem.annualReturn == newItem.annualReturn
&& oldItem.name == newItem.name)
}
}
interface OnAccountClickListener {
fun onAccountClick(account: Account)
}
interface OnItemDragged {
fun onItemSelected()
fun onItemClear()
}}
ItemTouchHelper
private fun setupListAdapter() {
accountListAdapter = AccountListAdapter(this)
accountListAdapter.setHasStableIds(true)
accounts_recycler_view.adapter = accountListAdapter
accounts_recycler_view.addItemDecoration(
DividerItemDecoration(
requireContext(),
DividerItemDecoration.VERTICAL
)
)
val accountTouchHelper = ItemTouchHelper(
object : ItemTouchHelper.SimpleCallback(
ItemTouchHelper.UP or ItemTouchHelper.DOWN,
0
) {
override fun onSelectedChanged(
viewHolder: RecyclerView.ViewHolder?,
actionState: Int
) {
if (actionState == ItemTouchHelper.ACTION_STATE_DRAG) {
val accountViewHolder = viewHolder as AccountListAdapter.ViewHolder
accountViewHolder.onItemSelected()
}
super.onSelectedChanged(viewHolder, actionState)
}
override fun clearView(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder
) {
val accountViewHolder = viewHolder as AccountListAdapter.ViewHolder
accountViewHolder.onItemClear()
super.clearView(recyclerView, viewHolder)
}
override fun onMove(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder,
target: RecyclerView.ViewHolder
): Boolean {
val fromPos: Int = viewHolder.adapterPosition
val toPos: Int = target.adapterPosition
Collections.swap(_accountList, fromPos, toPos)
accountListAdapter.notifyItemMoved(fromPos, toPos)
return true
}
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {}
})
accountTouchHelper.attachToRecyclerView(accounts_recycler_view)
}
所以问题是我的 Recyclerview
在 ViewPager
里面,而 ViewPager
在 ConstraintLayout
里面。 View pager 被垂直限制,高度设置为 0dp,但宽度设置为 match_parent
。我所需要的只是将宽度设置为 0dp 并将 setHasFixedSize = true
设置为 RecyclerView
水平约束
adapter调用notifyItemMoved
时,如果RecyclerView
灵活,则重绘所有item,默认聚焦第一个item。
我有一个奇怪的错误,每当我开始在其中拖动项目时,我的 RecyclerView
就会滚动回到顶部位置。如果有任何区别,它在 ViewPager
内。您可以在附加的 .gif 中看到行为。
编辑:
当 notifyItemMoved
被调用时,RecyclerView
视图似乎滚动到顶部,并且它滚动到第一个视图至少部分显示在屏幕上。
查看
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/accounts_recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbarStyle="outsideOverlay"
android:scrollbars="none"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
tools:listitem="@layout/view_account_list_item" />
适配器
class AccountListAdapter(
private val onAccountClickListener: OnAccountClickListener) :
ListAdapter<Account, AccountListAdapter.ViewHolder>(
AccountDiffCallback()
) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val inflater = LayoutInflater.from(parent.context)
return ViewHolder(
inflater.inflate(
R.layout.view_account_list_item,
parent,
false
)
)
}
override fun getItemId(position: Int): Long {
return getItem(position).accountId.toLong()
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.bind(getItem(position), onAccountClickListener)
}
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView), OnItemDragged {
fun bind(account: Account, onAccountClickListener: OnAccountClickListener) {
itemView.account_name.text = account.name
itemView.setOnClickListener {
onAccountClickListener.onAccountClick(account)
}
}
override fun onItemSelected() {
itemView.setBackgroundColor(
ContextCompat.getColor(
itemView.context,
R.color.background_contrast
)
)
}
override fun onItemClear() {
itemView.setBackgroundColor(
ContextCompat.getColor(
itemView.context,
R.color.background
)
)
}
}
class AccountDiffCallback : DiffUtil.ItemCallback<Account>() {
override fun areItemsTheSame(oldItem: Account, newItem: Account): Boolean {
return oldItem.accountId == newItem.accountId
}
override fun areContentsTheSame(oldItem: Account, newItem: Account): Boolean {
return (oldItem.balance == newItem.balance
&& oldItem.annualReturn == newItem.annualReturn
&& oldItem.name == newItem.name)
}
}
interface OnAccountClickListener {
fun onAccountClick(account: Account)
}
interface OnItemDragged {
fun onItemSelected()
fun onItemClear()
}}
ItemTouchHelper
private fun setupListAdapter() {
accountListAdapter = AccountListAdapter(this)
accountListAdapter.setHasStableIds(true)
accounts_recycler_view.adapter = accountListAdapter
accounts_recycler_view.addItemDecoration(
DividerItemDecoration(
requireContext(),
DividerItemDecoration.VERTICAL
)
)
val accountTouchHelper = ItemTouchHelper(
object : ItemTouchHelper.SimpleCallback(
ItemTouchHelper.UP or ItemTouchHelper.DOWN,
0
) {
override fun onSelectedChanged(
viewHolder: RecyclerView.ViewHolder?,
actionState: Int
) {
if (actionState == ItemTouchHelper.ACTION_STATE_DRAG) {
val accountViewHolder = viewHolder as AccountListAdapter.ViewHolder
accountViewHolder.onItemSelected()
}
super.onSelectedChanged(viewHolder, actionState)
}
override fun clearView(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder
) {
val accountViewHolder = viewHolder as AccountListAdapter.ViewHolder
accountViewHolder.onItemClear()
super.clearView(recyclerView, viewHolder)
}
override fun onMove(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder,
target: RecyclerView.ViewHolder
): Boolean {
val fromPos: Int = viewHolder.adapterPosition
val toPos: Int = target.adapterPosition
Collections.swap(_accountList, fromPos, toPos)
accountListAdapter.notifyItemMoved(fromPos, toPos)
return true
}
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {}
})
accountTouchHelper.attachToRecyclerView(accounts_recycler_view)
}
所以问题是我的 Recyclerview
在 ViewPager
里面,而 ViewPager
在 ConstraintLayout
里面。 View pager 被垂直限制,高度设置为 0dp,但宽度设置为 match_parent
。我所需要的只是将宽度设置为 0dp 并将 setHasFixedSize = true
设置为 RecyclerView
adapter调用notifyItemMoved
时,如果RecyclerView
灵活,则重绘所有item,默认聚焦第一个item。