使用ItemTouchHelper

问题描述

我有一个奇怪的错误，当我开始在其中拖动项目时，我的RecyclerView会滚动回到顶部位置。如果有任何区别，它位于ViewPager内部。您可以在.gif附件中看到该行为。

编辑：

当调用RecyclerView时，notifyItemmoved视图似乎滚动到顶部，并且它的滚动程度与第一视图至少部分地显示在屏幕上一样。

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)

}

解决方法

问题是我的Recyclerview在ViewPager内部，而ConstraintLayout在match_parent内部。视图分页器在垂直方向上受到限制，高度设置为0dp，但是宽度设置为setHasFixedSize = true。我所需要做的是将宽度水平设置为0dp，将RecyclerView设置为notifyItemMoved

在调用RecyclerView作为适配器时，如果const User = require("../models/user"); exports.signup = (req,res) => { const user = new User(req.body); user.save((err,user) => { if(err || !user){ return res.status(400).json({ err: "NOT able to save user in DB" }) } res.json({ name: user.name,email: user.email,id: user._id }); }); }; exports.signout = (req,res) => { res.json({ message: "User signout" }); }; 是灵活的，则将重绘所有项目，并且默认情况下，它集中在第一个项目上。