Android RecyclerView点击条目时如何修改其他holder的视图背景

问题根源 #

你当前的代码存在两个核心问题：

1. 点击事件中直接遍历数据列表尝试修改其他条目样式是无效的，RecyclerView只会持有当前可见条目的Holder实例，不可见的条目你无法直接拿到对应实例修改样式
2. 你在onBind方法中将条目背景写死为灰色，每次Holder复用的时候都会覆盖你之前修改的背景状态，滑动后选中状态会直接错乱

修改步骤 #

1. Adapter新增选中位置记录变量 #

在Adapter类中新增成员变量记录当前选中的条目位置，默认值可以根据需求设置为0（默认选中第一个）或者-1（默认无选中）

private var selectedPosition = 0

2. 改造onBind方法的背景设置逻辑 #

不要写死背景样式，根据当前position是否为选中位置动态设置背景：

// 删掉原来固定写死灰色背景的代码，替换成下面的逻辑
if (position == selectedPosition) {
    linear_background.background = context.getDrawable(R.drawable.shape_white_gift_recycler_stroke)
} else {
    linear_background.background = context.getDrawable(R.drawable.shape_gray_gift_recycler_stroke)
}

3. 改造点击事件逻辑 #

点击时只需要更新选中位置，调用刷新方法让RecyclerView重新渲染所有可见条目即可，不需要手动遍历修改每个Holder的样式

setOnClickListener {
    val preSelectedPos = selectedPosition
    selectedPosition = position
    // 局部刷新新旧两个选中位置，性能优于全局刷新notifyDataSetChanged()
    notifyItemChanged(preSelectedPos)
    notifyItemChanged(selectedPosition)
    viewModel?.getBrandItemsResult(item[position].categorySeq)
}

修改后完整代码 #

class GiftShowCategoryAdapterHolder(parent: ViewGroup) : RecyclerView.ViewHolder(
    LayoutInflater.from(parent.context).inflate(R.layout.item_giftshow_category, parent, false)
) {
    fun onBind(item: ArrayList<GiftCardResponse.brandCategories>, viewModel: GiftShowViewModel?, position: Int, selectedPosition: Int) {
        itemView.run {
            val displaymetrics = DisplayMetrics()
            (context as Activity).windowManager.defaultDisplay.getMetrics(displaymetrics)
            val devicewidth: Int = displaymetrics.widthPixels / 4
            val deviceheight: Int = displaymetrics.heightPixels / 8

            iv_giftshow_category.layoutParams.width = devicewidth
            iv_giftshow_category.layoutParams.height = deviceheight

            Glide.with(this).load(item[position].categoryIcon).error(R.drawable.choice_cash)
                .into(iv_giftshow_category)

            tv_giftshow_category.text = item[position].categoryName

            // 动态设置背景
            if (position == selectedPosition) {
                linear_background.background = context.getDrawable(R.drawable.shape_white_gift_recycler_stroke)
            } else {
                linear_background.background = context.getDrawable(R.drawable.shape_gray_gift_recycler_stroke)
            }

            setOnClickListener {
                val preSelected = selectedPosition
                selectedPosition = position
                notifyItemChanged(preSelected)
                notifyItemChanged(selectedPosition)
                viewModel?.getBrandItemsResult(item[position].categorySeq)
            }
        }
    }
}

private var giftShowCategoryList = ArrayList<GiftCardResponse.brandCategories>()
// 新增选中位置记录
private var selectedPosition = 0
private var viewModel: GiftShowViewModel? = null

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) = GiftShowCategoryAdapterHolder(parent);

override fun getItemCount() = giftShowCategoryList.size

override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
    (holder as? GiftShowCategoryAdapterHolder)?.onBind(giftShowCategoryList, viewModel, position, selectedPosition)
}

fun addItem(items: List<GiftCardResponse.brandCategories>) {
    giftShowCategoryList = items as ArrayList<GiftCardResponse.brandCategories>
}

fun addViewModel(viewModel: GiftShowViewModel) {
    this.viewModel = viewModel
}

内容的提问来源于stack exchange，提问作者Duseop