使用按钮单击删除RecyclerView和Dao中的项目

Question

我有一个显示来自Dao的数据的RecyclerView。在recyclerView中显示的数据中有一个用来删除项目的按钮。

我知道它的功能是：

fun deleteReceipt(receipts: Receipts) = viewModelScope.launch {
    receiptDao.delete(receipts)
}

但我不太确定该把它放在哪里并调用它。因为如果要在设置其他显示项值的Adapter中调用它，则无法访问Dao

以下是代码片段：

@AndroidEntryPoint
class HistoryFragment : Fragment(R.layout.fragment_history) {

private val viewModel: PurchaseViewmodel by viewModels()




override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    val binding = FragmentHistoryBinding.bind(view)

    val exampleAdapter = ExampleAdapter()

    binding.apply{
        recyclerView.apply{

            layoutManager = LinearLayoutManager(requireContext())
            adapter = exampleAdapter
            setHasFixedSize(true)
        }
    }

    setFragmentResultListener("add_receipt_request"){_,bundle ->
        val result = bundle.getInt("add_receipt_request")
        viewModel.onAddResult(result)
    }

    viewModel.receipts.observe(viewLifecycleOwner){ /// New Items get passed to the List
        exampleAdapter.submitList(it)
    }
}
}

ViewModel：

@HiltViewModel
class PurchaseViewmodel @Inject constructor(
private val receiptDao: ReceiptDao
    ): ViewModel() {
private val tasksEventChannel = Channel<TasksEvent>()
val addTaskEvent = tasksEventChannel.receiveAsFlow()
        val receipts = receiptDao.getAllReceipts().asLiveData()

fun onAddResult(result: Int){
    when (result){
        ADD_RECEIPT_RESULT_OK ->showReceiptSavedConfirmation("Receipt is saved")
    }
}
private fun showReceiptSavedConfirmation (text: String) = viewModelScope.launch {
    tasksEventChannel.send(TasksEvent.ShowReceiptSavedConfirmation(text))
}

fun deleteReceipt(receipts: Receipts) = viewModelScope.launch {
    receiptDao.delete(receipts)
}

sealed class TasksEvent {
    data class ShowReceiptSavedConfirmation(val msg: String) : TasksEvent()
}
}

和适配器：

class ExampleAdapter : ListAdapter<Receipts,ExampleAdapter.ExampleViewHolder>(DiffCallback()) {

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ExampleViewHolder { // Basically how to get a new Item from the List and display it
    val binding = ReceiptsBinding.inflate(LayoutInflater.from(parent.context),parent,false)
    return ExampleViewHolder(binding)
}

override fun onBindViewHolder(holder: ExampleViewHolder, position: Int) {
    val currentItem = getItem(position)
    holder.bind(currentItem)
}

override fun getItemCount(): Int {
    return super.getItemCount()
}

class ExampleViewHolder(private val binding: ReceiptsBinding) : RecyclerView.ViewHolder(binding.root){ //Examples One Row in our list
    fun bind (receipts: Receipts) {
        binding.apply {
            storeHistory.text = receipts.store
            amountHistory.text = receipts.total
            dateHistory.text  = receipts.date
        }
    }
}
class DiffCallback : DiffUtil.ItemCallback<Receipts>() {
    override fun areItemsTheSame(oldItem: Receipts, newItem: Receipts) =
        oldItem.id == newItem.id

    override fun areContentsTheSame(oldItem: Receipts, newItem: Receipts) =
        oldItem == newItem
}
}

Answer 1

使用此方法创建侦听器适配器中的listener in Fragment

• Create listener变量将侦听器从片段传递到适配器Interface

• Implement将侦听器传递到viewHolder

• on删除按钮单击该项调用listener方法，这将触发片段中的实现，您可以使用viewModel.deleteReceipt

访问ViewModel

• delete