我應該怎么辦？我在TabLayout片段中的片段上使用的RecyclerView不會顯示

我正在嘗試在 TabLayout 中的片段上顯示 RecyclerView，該片段也是片段。但是，即使沒有錯誤，RecyclerView 仍然拒絕顯示。根據我收集的資訊，TabLayout 的片段應該有可能具有 RecyclerView。但是，我不知道問題是否在于我在片段上構建 TabLayout 導致 recyclerview 不顯示。我想我一定是做錯了什么，我需要一些幫助。這是我的代碼：

TabLayoutFragment

    var viewPager = root.findViewById(R.id.viewPager) as ViewPager
    var tablayout = root.findViewById(R.id.tabLayout) as TabLayout

    val fragmentAdapter = FragmentAdapter(requireActivity().supportFragmentManager)
    fragmentAdapter.addFragment(OpenLoansFragment(), "Active")
    fragmentAdapter.addFragment(ClosedLoansFragment(), "Closed")

    viewPager.adapter = fragmentAdapter
    tablayout.setupWithViewPager(viewPager)

RecyclerView 片段

private lateinit var swipeRefreshLayout:SwipeRefreshLayout
private lateinit var loanRecRcv:RecyclerView
private var list: ArrayList<LoanRecordModel> = ArrayList()
private var loanRecRcvAdapter = LoanRecRcvAdapter(list, this)

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {

    _binding = FragmentOpenLoansBinding.inflate(inflater, container, false)
    val root: View = binding.root

    return root
}

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

    list = arrayListOf(
        LoanRecordModel("", "Petty Cash Loan", "12/05/2022", "Open"),
        LoanRecordModel("", "Petty Cash Loan", "12/05/2022", "Open"),
        LoanRecordModel("", "Petty Cash Loan", "12/05/2022", "Open"),
        LoanRecordModel("", "Petty Cash Loan", "12/05/2022", "Open"),
        LoanRecordModel("", "Petty Cash Loan", "12/05/2022", "Open")

    )

    initView()

    loanRecRcv.apply{
        layoutManager = LinearLayoutManager(activity)
        adapter = loanRecRcvAdapter
    }
}

private fun initView() {

    swipeRefreshLayout = requireActivity().findViewById(R.id.swipeRefresh)
    loanRecRcv = requireActivity().findViewById(R.id.loanRecRcv)

}

uj5u.com熱心網友回復：

您在RecyclerView. 首先，您在構建時創建一個空配接器：

// empty list
private var list: ArrayList<LoanRecordModel> = ArrayList()
// adapter created with the empty list
private var loanRecRcvAdapter = LoanRecRcvAdapter(list, this)

稍后您將該配接器應用到您的 RV：

loanRecRcv.apply{
    ...
    adapter = loanRecRcvAdapter
}

您正在創建一個專案串列onViewCreated

list = arrayListOf(
    LoanRecordModel("", "Petty Cash Loan", "12/05/2022", "Open"),
    ...
)

但這正在替換存盤在list變數中的串列。您已經Adapter使用原始串列創建了較早的（構建時），因此它仍在內部使用該空串列。它沒有參考您的list變數。

兩個基本選項 - 創建list一個MutableList并更新其內容而不是替換它：

// empty mutable list - you never need to actually use ArrayLists or whatever
// made it a val so you can't replace it!
private val list = mutableListOf<LoanRecordModel>()
// pass that list object to the adapter, so it's shared
private var loanRecRcvAdapter = LoanRecRcvAdapter(list, this)

...

// update your list contents
list.addAll(listOf(
    LoanRecordModel("", "Petty Cash Loan", "12/05/2022", "Open"),
    ...
))
// notify the adapter that it needs to refresh since its data set (the shared list) has changed
adapter.notifyDataSetChanged()

或者（更好）只是將新資料傳遞給配接器并讓它在內部存盤，處理自身更新等：

// in your adapter

// store the current data here - initially an empty list, so it can still display
private var list: List<LoanRecordModel> = emptyList()

fun setData(data: List<LoanRecordModel>) {
    // calling toList makes a new list object - even if the 'data' list object gets
    // modified later, we have our own internal list object that won't be affected
    list = data.toList()
    // update the display however you like
    notifyDataSetChanged()
}

// in your fragment

adapter.setData(listOf(
    LoanRecordModel("", "Petty Cash Loan", "12/05/2022", "Open"),
    ...
))

這種方式更好，因為配接器的資料集是在內部保存的，而不是在您的片段中。您有一個簡單的setData函式來獲取新資料，并根據需要處理更新配接器。呼叫者不需要知道這些，它只是傳遞資料。您也可以從 ' 的建構式中洗掉您的List引數Adapter- 無論如何您都沒有將它初始化為一個空串列 - 現在這是該內部list屬性的默認值

順便說一句，要初始化相同事物的串列，您可以這樣做

// create an immutable list
val list = List(5) { LoanRecordModel("", "Petty Cash Loan", "12/05/2022", "Open") }

// or add to a mutable list
list.addAll(List(5) { LoanRecordModel("", "Petty Cash Loan", "12/05/2022", "Open") })

// or another way
repeat(5) {
    list.add(LoanRecordModel("", "Petty Cash Loan", "12/05/2022", "Open"))
}

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