如何制作删除按钮以删除kotlin中的recyclerview项目？

Question

我在主要活动上创建了selectDelete 按钮，而不是RecyclerView。 当我单击该按钮时，我想删除选中的项目。 检查RecyclerView项目复选框并在滚动时取消选中项目时出现错误。

---

活动

class CartViewActivity : AppCompatActivity(), SwipeRefreshLayout.OnRefreshListener {

    private val tag = this::class.java.simpleName

    lateinit var adapter: CartItemRecyclerAdapter

    var itemList: MutableList<CartItemDataVo> = arrayListOf()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_cart_view)

        selectDelete.setOnClickListener {

            if (checkBox.isChecked) {
                  *adapter.removeItems()*
            }
        }

        swipeRefreshLo.setOnRefreshListener(this)

        itemList.add(CartItemDataVo("item1", 1, 16800, "cart_doll", false))
        itemList.add(CartItemDataVo("item2", 1, 16800, "cart_cup", false))
        itemList.add(CartItemDataVo("item3", 1, 30000, "cart_perfume", false))
        itemList.add(CartItemDataVo("item4", 1, 16800, "cart_fan", false))

        adapter = CartItemRecyclerAdapter(this, this, itemList)
        recycler_view.adapter = adapter
        recycler_view.layoutManager =
            androidx.recyclerview.widget.LinearLayoutManager(applicationContext)
    }

    override fun onRefresh() {
        swipeRefreshLo.isRefreshing = false
    }
}

---

适配器：

class CartItemDataVo(
    title: String,
    itemNumber: Int,
    pointValue: Int,
    imageView: String,
    CheckBox: Boolean
) {
    var title: String = title
    var itemNumber: Int = itemNumber
    var pointValue: Int = pointValue
    var image: String = imageView
    var isChecked: Boolean = CheckBox
}

class CartItemRecyclerAdapter(
    val context: Context,
    private var activity: Activity,
    private var dataList: MutableList<CartItemDataVo>
) : RecyclerView.Adapter<CartItemRecyclerAdapter.Holder>() {

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

    override fun onBindViewHolder(holder: Holder, position: Int) {
        holder?.bind(dataList[position], context)
    }

    override fun getItemCount(): Int = dataList.size


    *@SuppressLint("NewApi")
    fun removeItems() {
        dataList.removeIf { it.isChecked }
        notifyDataSetChanged()
     }*

    fun toggleItems() {
        for (item: CartItemDataVo in dataList) {
            var state = item.isChecked
            item.isChecked = state.not()
        }
        notifyDataSetChanged()
    }

    inner class Holder(itemView: View?) : RecyclerView.ViewHolder(itemView!!) {

        var titleText = itemView?.findViewById(R.id.titleText) as TextView
        var temNumerTextt = itemView?.findViewById(R.id.textViewItemNumer) as TextView
        var pointValueText = itemView?.findViewById(R.id.pointValueText) as TextView
        var imageView = itemView?.findViewById(R.id.imageView) as ImageView
        var checkBox = itemView?.findViewById(R.id.checkBox) as CheckBox

        fun bind(data: CartItemDataVo, context: Context) {
            if (data.image != "") {
                val resourceId =
                    context.resources.getIdentifier(data.image, "drawable", context.packageName)
                imageView?.setImageResource(resourceId)
            } else {
                imageView.setImageResource(R.mipmap.ic_launcher)
            }
            titleText?.text = data.title
            temNumerTextt?.text = data.itemNumber.toString()
            pointValueText?.text = data.pointValue.toString() + "P"

            if (data.isChecked) {
                checkBox.buttonDrawable =
                    checkBox.context.getDrawable(R.drawable.check_box_active_cs)
                val layout = activity?.findViewById(R.id.layoutOrder) as LinearLayout
                layout.visibility = View.VISIBLE
            } else {
                checkBox.buttonDrawable = checkBox.context.getDrawable(R.drawable.check_box_no)
                val layout = activity?.findViewById(R.id.layoutOrder) as LinearLayout
                layout.visibility = View.GONE
            }


            checkBox?.setOnClickListener {
                if (checkBox.isChecked == data.isChecked) {
                    checkBox.buttonDrawable = it.context.getDrawable(R.drawable.check_box_active_cs)
                    val layout = activity?.findViewById(R.id.layoutOrder) as LinearLayout
                    layout.visibility = View.VISIBLE
                } else {
                    checkBox.buttonDrawable = it.context.getDrawable(R.drawable.check_box_no)
                    val layout = activity?.findViewById(R.id.layoutOrder) as LinearLayout
                    layout.visibility = View.GONE
                }

            }
        }
    }
}

Answer 1

首先，替换

var itemList: MutableList<CartItemDataVo> = arrayListOf()

与

val itemList: MutableList<CartItemDataVo> = arrayListOf()

你不想要可变属性，它同时也是可变集合。这是非常糟糕的做法。

适配器中的相同情况

private var dataList : MutableList<CartItemDataVo>

替换为

private val dataList : MutableList<CartItemDataVo>

---

然后从适配器的构造函数中删除private var activity : Activity。不要在适配器中放置任何对Activity 或Fragment 的引用！

适配器应该只负责显示列表。

如果在任何情况下，您需要Activity 或Fragment 与适配器之间的通信，请改用接口。这不是ViewHolder 负责持有对父布局的引用并对其进行操作！

val layout = activity?.findViewById(R.id.layoutOrder) as LinearLayout

应从ViewHolder 中删除如下所有行。如果你需要设置属于Activity的东西，基于列表上的动作，使用接口。

---

最后，在适配器的 add 方法中删除选中的项目：

fun removeItems() {
    itemList.removeIf { it.isChecked }
    notifyDataSetChanged()
}

在checkBox?.setOnClickListener { 之后添加以下行（作为侦听器的第一行）

data.isChecked = !data.isChecked

并替换

selectDelete.setOnClickListener {

    if(checkBox.isChecked){


    }
}

与

selectDelete.setOnClickListener {

    if(checkBox.isChecked){
        adapter?.removeItems()
    }
}

---

奖金：

• 阅读 data class，并将其用于 CartItemDataVo（不要在构造函数中使用 CheckBox），

• updateData 方法可以使用DiffUtil 优化RecyclerView，

• 可以通过修改Activity中的数据来改进，而不是在适配器中，所以负责人会被转移到更好的地方，

• 了解 SOLID 原则，

• 了解 MVVM 和 MVP 设计模式。