改变RecyclerView中未选择/选中的项目的颜色

Question 1

我的问题是，我想在一个 RecyclerView 中选择一个项目，它应该改变颜色，如果我点击另一个项目，第一个被选中的项目应该改变为默认颜色（最后一个被点击的项目应该有被选中的颜色）。

我已经改变了所选项目的颜色，如果我再次点击所选项目，它就会变成默认颜色。现在我只想知道，如果我点击一个未选择的项目，如果我已经选择了一个项目，它们的颜色就会 "切换"。

这是我的SubItem类。

class SubItem(val channel: Channel) : Item<GroupieViewHolder>() {
    @SuppressLint("ResourceAsColor")
    override fun bind(viewHolder: GroupieViewHolder, position: Int) {
        val profileImageUrl =  channel.channel_logo
        viewHolder.itemView.sub_item_name.text = channel.channel_name
        viewHolder.itemView.sub_item_layout.setBackgroundResource(R.color.white)
        viewHolder.itemView.sub_item_name.setTextColor(R.color.colorSecondaryText)
        val targetImageView = viewHolder.itemView.sub_item_profile
        try {
            Picasso.get().load(profileImageUrl)
                .placeholder(R.drawable.ic_baseline_account_circle_24)
                .into(targetImageView)
        }catch (e:Exception){
            Log.d("SubItem","${e.message}")
        viewHolder.itemView.sub_item_layout.setOnClickListener {
            if (selected_position == position){
                selected_position = null
                viewHolder.itemView.sub_item_layout.setBackgroundResource(R.color.white)
                viewHolder.itemView.sub_item_name.setTextColor(R.color.colorSecondaryText)
            else{
                selected_position = position
                viewHolder.itemView.sub_item_layout.setBackgroundResource(R.color.colorSecondaryText)
                viewHolder.itemView.sub_item_name.setTextColor(R.color.black)
    override fun getLayout(): Int {
        return R.layout.subscription_item
如果有帮助的话，这是我的函数，我把项目添加到RecyclerView中。
private fun fetchSubs() {
        val uid = auth.uid
        val user = database.getReference("/users/$uid/subscriptions")
        val adapter = GroupAdapter<GroupieViewHolder>()
        user.addListenerForSingleValueEvent(object : ValueEventListener{
            @SuppressLint("NotifyDataSetChanged")
            override fun onDataChange(p0: DataSnapshot) {
                p0.children.forEach{
                    val sub = it.getValue(Subscription::class.java) ?: return
                    if (sub.subscribed == true) {
                        val ref = database.getReference("/channels/${sub.channel_uid}")
                        ref.addListenerForSingleValueEvent(object : ValueEventListener {
                            override fun onDataChange(p0: DataSnapshot) {
                                val channel = p0.getValue(Channel::class.java) ?: return
                                adapter.add(SubItem(channel))
                            override fun onCancelled(error: DatabaseError) {
                adapter.setOnItemClickListener{ item, view ->
                    val subItem = item as SubItem
                    val channelName = subItem.channel.channel_name
                    val channelUid = subItem.channel.uid
                    Toast.makeText(requireContext(),"$channelName : $channelUid", Toast.LENGTH_SHORT).show()
                    fetchSubs()
                sub_recyclerview.adapter = adapter
            override fun onCancelled(error: DatabaseError) {
对不起，我没有使用模型和适配器

Question 2


          
           
            For everyone who uses
            
             groupie
            
            like me this could help you in future.
           
           
            This is my solution for my Problem.
           
           
            
             SubItem类
            
           
           class SubItem(val channel: Channel) : Item<GroupieViewHolder>() {
    @SuppressLint("ResourceAsColor")
    override fun bind(viewHolder: GroupieViewHolder, position: Int) {
        val profileImageUrl =  channel.channel_logo
        viewHolder.itemView.sub_item_name.text = channel.channel_name
        val targetImageView = viewHolder.itemView.sub_item_profile
        try {
            Picasso.get().load(profileImageUrl)
                .placeholder(R.drawable.ic_baseline_account_circle_24)
                .into(targetImageView)
        }catch (e:Exception){
            Log.d("SubItem","${e.message}")
//            Toast.makeText(,e.message,Toast.LENGTH_SHORT).show()
        checkFilter(viewHolder,position)
    @SuppressLint("ResourceAsColor")
    private fun checkFilter(v: GroupieViewHolder, p: Int) {
        when (SubscriptionsFragment.list[p]) {
            true -> {
                v.itemView.sub_item_layout.setBackgroundResource(R.color.colorDivider)
                v.itemView.sub_item_name.setTextColor(R.color.black)
            false -> {
                v.itemView.sub_item_layout.setBackgroundResource(R.color.white)
                v.itemView.sub_item_name.setTextColor(R.color.colorSecondaryText)
    override fun getLayout(): Int {
        return R.layout.subscription_item
My function with setOnItemClickListener
private fun fetchSubs() {
        val uid = auth.uid
        val user = database.getReference("/users/$uid/subscriptions")
        val adapter = GroupAdapter<GroupieViewHolder>()
        user.addListenerForSingleValueEvent(object : ValueEventListener{
            @SuppressLint("NotifyDataSetChanged")
            override fun onDataChange(p0: DataSnapshot) {
                list = mutableListOf()
                p0.children.forEach{
                    val sub = it.getValue(Subscription::class.java) ?: return
                    if (sub.subscribed == true) {
                        val ref = database.getReference("/channels/${sub.channel_uid}")
                        ref.addListenerForSingleValueEvent(object : ValueEventListener {
                            override fun onDataChange(p0: DataSnapshot) {
                                val channel = p0.getValue(Channel::class.java) ?: return
                                list.add(false) // created in companion object: var list =  mutableListOf<Boolean>()
                                oldList.add(false) // created in companion object: var oldlist =  mutableListOf<Boolean>()
                                adapter.add(SubItem(channel))
                            override fun onCancelled(error: DatabaseError) {
                adapter.setOnItemClickListener{ item, view ->
                    val subItem = item as SubItem
                    val pos = adapter.getAdapterPosition(subItem)
                    // Here happens the magic
                    list[pos] = !list[pos] // change selected item from false to true or from true to false
                    val l = list[pos] // saving Boolean
                    list = mutableListOf()
                    oldList.forEach{ // using oldList to loop so many times I need
                        list.add(false) // setting all to false
                    if (l){ // if Boolean is true
                        list[pos] = !list[pos] // change selected item from false to true
                    val channelUid = subItem.channel.uid
                    fetchVideos(channelUid)
                    adapter.notifyDataSetChanged() // refresh all items in SubItem
                try {
                    sub_recyclerview.adapter = adapter
                } catch(e:Exception){
                    Log.d("fetchSubs","${e.message}")
            override fun onCancelled(error: DatabaseError) {