Question

我有一个用Kotlin编写的购物车应用程序的RecyclerViewAdapter。当用户更改购物车中的物品数量时，我想用当前购物车总数更新ActionBar的标题。

我已经看过使用回调，侦听器和传递上下文的各种代码，以尝试从RecyclerViewAdapter访问ActionBar，但是我不知道它们是否适用于Kotlin，或者总是将所有内容都保留下来也没有太大意义。在RecyclerViewAdapter中的代码（数据库查找，写入，CardView更新等）

以下是我的调用代码和RecyclerViewAdapter的高度缩写代码（但我希望我拥有所有重要的组件）：

class ItemRecyclerViewAdapter(private val itemArray: MutableList<ItemObject>, private val contextABC: Context) : RecyclerView.Adapter<ItemRecyclerViewAdapter.ViewHolder>() {

    inner class ViewHolder(v: View) : RecyclerView.ViewHolder(v) {
        private val cardViewAdd: Button

        init {
            cardViewAdd = v.findViewById<View>(R.id.cardview_item_Add) as Button

            // Add one to Qty Ordered
            cardViewAdd.setOnClickListener { updateItemQty(adapterPosition, itemArray[adapterPosition].qtyOrdered + 1, v) }
        }
    }

private fun updateItemQty(arrayPosition: Int, pQtyOrdered: Int, v: View) {
            itemArray[arrayPosition].qtyOrdered = pQtyOrdered
            notifyItemChanged(arrayPosition)
    }
}

class CartActivity : BaseActivity() {
    internal var cartItemsList: MutableList<ItemObject> = ArrayList()

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

        cartItemsList = DatabaseAdapter.cartItems
        cart_RecyclerView.setHasFixedSize(true)
        cart_RecyclerView.layoutManager = LinearLayoutManager(this)
        rvAdapter = ItemRecyclerViewAdapter(cartItemsList, this)
        cart_RecyclerView.adapter = rvAdapter
    }
}

有人可以让我朝正确的方向前进吗？我当然感谢您的帮助！

[编辑] 在Birju Vachhani的大力帮助下，这是我的工作代码：

class ItemRecyclerViewAdapter(private val itemArray: MutableList<ItemObject>,
    private val contextABC: Context, val updateActionBarTitle: (ItemObject) -> Unit = {})
 : RecyclerView.Adapter<ItemRecyclerViewAdapter.ViewHolder>() {

    inner class ViewHolder(v: View) : RecyclerView.ViewHolder(v) {
        private val cardViewAdd: Button

        init {
            cardViewAdd = v.findViewById<View>(R.id.cardview_item_Add) as Button

            // Add one to Qty Ordered
            cardViewAdd.setOnClickListener { updateItemQty(adapterPosition, itemArray[adapterPosition].qtyOrdered + 1, v) }
        }
    }

private fun updateItemQty(arrayPosition: Int, pQtyOrdered: Int, v: View) {
            itemArray[arrayPosition].qtyOrdered = pQtyOrdered
            notifyItemChanged(arrayPosition)
            updateActionBarTitle(itemArray[arrayPosition])
    }
}

class CartActivity : BaseActivity() {
    internal var cartItemsList: MutableList<ItemObject> = ArrayList()

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

        cartItemsList = DatabaseAdapter.cartItems
        cart_RecyclerView.setHasFixedSize(true)
        cart_RecyclerView.layoutManager = LinearLayoutManager(this)
        rvAdapter = ItemRecyclerViewAdapter(cartItemsList, this){item->
            supportActionBar?.setTitle("hi")
        }
        cart_RecyclerView.adapter = rvAdapter
    }
}

Answer 1

您可以通过使用Kotlin的lambda函数来做到这一点：

适配器：

class ItemRecyclerViewAdapter(
    private val itemArray: MutableList<ItemObject>,
    val onItemAdded: (ItemObject) -> Unit = {}
) :
    RecyclerView.Adapter<ItemRecyclerViewAdapter.ViewHolder>() {

    override fun getItemCount(): Int {
        return itemArray.size
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return ViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.item_layout,parent,false))
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.cardViewAdd.setOnClickListener {
            updateItemQty(position, itemArray[position].qtyOrdered + 1)
            onItemAdded(itemArray[position])
        }
    }

    class ViewHolder(v: View) : RecyclerView.ViewHolder(v) {
        val cardViewAdd: Button = v.findViewById(R.id.cardview_item_Add)

        fun bind(item:ItemObject){
            // bind your data with view here
        }
    }

    fun updateItemQty(arrayPosition: Int, pQtyOrdered: Int) {
        itemArray[arrayPosition].qtyOrdered = pQtyOrdered
        notifyItemChanged(arrayPosition)
    }
}

在您的活动中：

CartActivity类：BaseActivity（）{ 内部var cartItemsList：MutableList = ArrayList（）

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

    cartItemsList = DatabaseAdapter.cartItems
    cart_RecyclerView.setHasFixedSize(true)
    cart_RecyclerView.layoutManager = LinearLayoutManager(this)
    rvAdapter = ItemRecyclerViewAdapter(cartItemsList, this){item->
        // here you can access your ActionBar as perform actions on it
    }
    cart_RecyclerView.adapter = rvAdapter
}

}

使用Kotlin更新Android RecyclerViewAdapter中的ActionBar

1 个答案: