如何仅修改父RecyclerView第0项中嵌套RecyclerView的首个子元素

要实现仅父RecyclerView第0项内的子RecyclerView首个元素加粗，核心是让子RecyclerView的Adapter知晓自己所属的父项位置，而非仅判断子项的position。

Kotlin 实现示例 #

1. 修改子Adapter，接收父项位置参数

class ChildAdapter(
    private val items: List<String>,
    private val parentPosition: Int // 新增父项位置参数
) : RecyclerView.Adapter<ChildAdapter.ChildViewHolder>() {

    inner class ChildViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val tvItem: TextView = itemView.findViewById(R.id.tv_child_item)
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ChildViewHolder {
        val view = LayoutInflater.from(parent.context)
            .inflate(R.layout.item_child, parent, false)
        return ChildViewHolder(view)
    }

    override fun onBindViewHolder(holder: ChildViewHolder, position: Int) {
        val itemText = items[position]
        holder.tvItem.text = itemText

        // 仅当父项是第0项，且子项是第0个时加粗
        if (parentPosition == 0 && position == 0) {
            holder.tvItem.typeface = Typeface.DEFAULT_BOLD
        } else {
            holder.tvItem.typeface = Typeface.DEFAULT
        }
    }

    override fun getItemCount() = items.size
}

2. 父Adapter绑定子RecyclerView时传入当前父项位置

class ParentAdapter(private val parentData: List<List<String>>) : RecyclerView.Adapter<ParentAdapter.ParentViewHolder>() {

    inner class ParentViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val rvChild: RecyclerView = itemView.findViewById(R.id.rv_child)
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ParentViewHolder {
        val view = LayoutInflater.from(parent.context)
            .inflate(R.layout.item_parent, parent, false)
        return ParentViewHolder(view)
    }

    override fun onBindViewHolder(holder: ParentViewHolder, position: Int) {
        val childItems = parentData[position]
        // 创建子Adapter时传入当前父项的position
        val childAdapter = ChildAdapter(childItems, position)
        holder.rvChild.apply {
            layoutManager = LinearLayoutManager(context)
            adapter = childAdapter
        }
    }

    override fun getItemCount() = parentData.size
}

适配复杂已有Adapter的方案 #

如果你的子Adapter已经比较复杂，不想修改构造函数，可以通过Setter方法传递父项位置：

修改后的子Adapter

class ChildAdapter(private val items: List<String>) : RecyclerView.Adapter<ChildAdapter.ChildViewHolder>() {
    private var parentPosition = -1

    // 新增Setter方法设置父项位置
    fun setParentPosition(pos: Int) {
        this.parentPosition = pos
        notifyDataSetChanged() // 触发列表更新
    }

    inner class ChildViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val tvItem: TextView = itemView.findViewById(R.id.tv_child_item)
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ChildViewHolder {
        val view = LayoutInflater.from(parent.context)
            .inflate(R.layout.item_child, parent, false)
        return ChildViewHolder(view)
    }

    override fun onBindViewHolder(holder: ChildViewHolder, position: Int) {
        val itemText = items[position]
        holder.tvItem.text = itemText

        if (parentPosition == 0 && position == 0) {
            holder.tvItem.typeface = Typeface.DEFAULT_BOLD
        } else {
            holder.tvItem.typeface = Typeface.DEFAULT
        }
    }

    override fun getItemCount() = items.size
}

父Adapter中设置父项位置

override fun onBindViewHolder(holder: ParentViewHolder, position: Int) {
    val childItems = parentData[position]
    // 复用已有Adapter或创建新的
    val childAdapter = holder.rvChild.adapter as? ChildAdapter ?: ChildAdapter(childItems)
    // 设置当前父项位置
    childAdapter.setParentPosition(position)
    holder.rvChild.adapter = childAdapter
}

关键说明 #

• 核心逻辑是同时判断父项位置和子项位置，避免仅通过子项position=0导致所有子列表首个元素加粗的问题。
• 由于RecyclerView存在ViewHolder复用机制，务必在父Adapter的onBindViewHolder中确保子Adapter的父项位置被正确更新，避免复用旧的配置。

内容的提问来源于stack exchange，提问作者Altohombre