如何在RecyclerView中只显示2项？

Question

有一个操作列表，我通过ListAdapter在回收视图中显示。RecyclerView的大小是两个元素。

ListAdapter：

class OperationAdapter(private val onItemClicked: (Operation) -> Unit) :
ListAdapter<Operation, OperationAdapter.OperationViewHolder>(DiffCallback) {



override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): OperationViewHolder {
    val viewHolder = OperationViewHolder(
        OperationItemBinding.inflate(
            LayoutInflater.from(parent.context),
            parent,
            false
        )
    )

    return viewHolder
}

@SuppressLint("ResourceAsColor", "SetTextI18n")
override fun onBindViewHolder(holder: OperationViewHolder, position: Int) {

    holder.bind(getItem(position))
}


class OperationViewHolder(private var binding: OperationItemBinding): RecyclerView.ViewHolder(binding.root) {
    /*val imageOperation:ImageView = view.findViewById(R.id.imageViewItem)
    val nameOperation:TextView = view.findViewById(R.id.name_operation)
    val balanceOperation:TextView = view.findViewById(R.id.textSum)*/
    fun bind(operation: Operation){
        if(operation.receive == ACCOUNT.number){
            binding.imageViewItem.setImageResource(R.drawable.ic_type_recieve)

            binding.nameOperation.text = operation.send
            binding.nameOperation.setTextColor(Color.rgb(35, 135, 0))

            val sum = NumberFormat.getCurrencyInstance(Locale("en", "US")).format(operation.sum)
            binding.textSum.text = sum
            binding.textSum.setTextColor(Color.rgb(35, 135, 0))
        }else{
            binding.imageViewItem.setImageResource(R.drawable.ic_type_sent)

            binding.nameOperation.text = operation.receive
            binding.nameOperation.setTextColor(Color.rgb(231, 223,255))

            val sum = NumberFormat.getCurrencyInstance(Locale("en", "US")).format(operation.sum)
            binding.textSum.text = "-$sum"
            binding.textSum.setTextColor(Color.rgb(231, 223,255))
        }
    }
}

companion object{
    private val DiffCallback = object: DiffUtil.ItemCallback<Operation>(){
        override fun areItemsTheSame(oldItem: Operation, newItem: Operation): Boolean {
            return oldItem.id == newItem.id
        }

        override fun areContentsTheSame(oldItem: Operation, newItem: Operation): Boolean {
            return oldItem == newItem
        }

    }
}

}

我从房间里从沙发检索到了清单：

  GlobalScope.launch(Dispatchers.IO){
        sharedViewModel.getOperationsAll(ACCOUNT.number).collect(){ it ->
            operationAdapter.submitList(it.sortedByDescending { it.time })
        }
    }

我不能输出只有两个项目的回收视图，用户可以滚动它。

Answer 1

您不能为此使用GlobalScope，因为它会在应用程序的整个生命周期内泄漏您的活动和/或片段。每次屏幕变化，它都会泄漏另一个拷贝，直到你的应用程序耗尽内存。

Dispatchers.IO是不必要的。您不能在这个协同线中调用任何阻塞函数。

若要限制为两项，可以在将列表传递给适配器之前在列表上使用take(2)：

lifecycleScope.launch {
    sharedViewModel.getOperationsAll(ACCOUNT.number).collect { opList ->
        operationAdapter.submitList(opList.sortedByDescending { it.time }.take(2))
    }
}

如果这是一个片段，则应该使用viewLifecycleOwner.lifecycleScope。