突出显示recyclerview的选定项目

Question

请不要将其标记为重复我指的是

出现异常：

kotlin.KotlinNullPointerException at package.name.ProductDetails.Custom_detail_Adapter.onBindViewHolder(Custom_detail_Adapter.kt:57)

这是行：

holder.relativeitem.setSelected(selectedItems?.get(position, false)!!);

而且我也想知道如何在加载时 setSelected 位于第一个位置 activity。（如何预填充SparseBooleanArray？）

这是我的适配器：

    class  Custom_detail_Adapter(context: Context, dataList: List<Product_images_response>) :
    RecyclerView.Adapter<Custom_detail_Adapter.CustomViewHolder>() {
    private val dataList: List<Product_images_response>
    private val context: Context
    private val selectedItems: SparseBooleanArray?=null

    inner class CustomViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView),View.OnClickListener {
        val mView: View

         val avatar: ImageView
         val relativeitem:RelativeLayout

        init {
            mView = itemView

            avatar = mView.findViewById(R.id.view3)
            relativeitem=mView.findViewById(R.id.relativeitem)
        }

        override fun onClick(v: View?) {
            if (selectedItems?.get(getAdapterPosition(), false)!!) {
                selectedItems?.delete(getAdapterPosition());
                relativeitem.setSelected(false);
            }
            else {
                selectedItems?.put(getAdapterPosition(), true);
                relativeitem.setSelected(true);
            }
        }

    }

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

    override fun onBindViewHolder(holder: CustomViewHolder, position: Int) {
        holder.relativeitem.setSelected(selectedItems?.get(position, false)!!);

     Glide.with(context).load(dataList[position].image)
            .thumbnail(0.5f)
            .diskCacheStrategy(DiskCacheStrategy.ALL)
            .into(holder.avatar)


        holder.avatar.setOnClickListener(View.OnClickListener {
           
            val intent = Intent("custom-message")
        
            intent.putExtra("item", dataList.get(position).image)
            LocalBroadcastManager.getInstance(context).sendBroadcast(intent)
        })
    }

    override fun getItemCount(): Int {
        return dataList.size
        //return (dataList == null) ? 0 : dataList.size();
    }

    init {
        this.context = context
        this.dataList = dataList
    }
    }

这是我的布局：

    <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:id="@+id/relativeitem"
    android:background="@drawable/activated_color_selector"
    android:layout_height="wrap_content">
    <ImageView
        android:layout_width="235px"
        android:layout_height="207px"
        android:id="@+id/view3"

        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp"
        android:layout_weight="1"
        />
        </RelativeLayout>

需要帮助！谢谢。

Answer 1

首先，给selectedItems变量一个初始值。也没有必要让它成为可选的，从而消除了用问号打开可选值的需要（这个 selectedItems? 变成了这个 selectedItems）：

private val selectedItems = SparseBooleanArray()

如果要在加载适配器之前设置选定位置，请将此变量设为构造函数参数之一。使用此主要构造函数，您可以删除 init 块：

class  Custom_detail_Adapter(private val context: Context, private val dataList: List<Product_images_response>, private val selectedItems: SparseBooleanArray) :
RecyclerView.Adapter<Custom_detail_Adapter.CustomViewHolder>() {

inner class CustomViewHolder ...

此 SparseBooleanArray 构造函数参数可以预先填充指示选择了哪些项目的值。

突出显示recyclerview的选定项目

highlight the selected item of recyclerview

android

selecteditem

kotlin

android-recyclerview