如何檢查串列中的值是否為空，如果沒有獲取值

我從這樣的服務器獲取串列

[
  {
    "Date": "2022-10-21",
    "Wages": [
      {
        "Name": "101 Working hours",
        "Balance": "8.00",
        "Date": "2022-10-21",
        "ShiftName": "AU128"
      },
      {
        "Name": "102 Bonus pay",
        "Balance": "3:48",
        "Date": "2022-10-21",
        "ShiftName": ""
      },
      {
        "Name": "110 Split Shift",
        "Balance": "1:00",
        "Date": "2022-10-21",
        "ShiftName": ""
      },
      {
        "Name": "111 Wage reduction",
        "Balance": "1:00",
        "Date": "2022-10-21",
        "ShiftName": ""
      }
    ]
  },
]

如果 ShiftName 不為空并在 FE 顯示，我想獲取它。班次名稱在工資單中

Text(
  Wages[i].shiftName ?? "",
  style: wageTextStyle,
),

我嘗試使用List.any((any) => any.containsValue());

但我不知道我從服務器得到哪個值，因為 shiftName 可以更改

我來自提供者消費者的 API 呼叫方法

            Consumer<EmployeeWageAccountsProvider>(
              builder: (context, data, child) {
              if (!data.isLoading) {
              int length = data.getEmployeeAccountsData!.length;
              if (data.getEmployeeAccountsData!.isNotEmpty) {
                wageAccountsData = data.getEmployeeAccountsData!;
                return ListView.builder(
                  itemCount: length,
                  shrinkWrap: true,
                  scrollDirection: Axis.vertical,
                  itemBuilder: (context, i) {
                    return WageAccountsCard(
                      date: Helper.formatStringDate(
                          wageAccountsData[i].date!),
                     shiftName: wageAccountsData[i].wages! 
         [i].shiftName!.isEmpty ? "":wageAccountsData[i].wages! 
               [i].shiftName,
                     wages: wageAccountsData[i].wages,
                    );
                  },
                );
              }
              return noDataFound(context, 50);
            }
            return const WageAccountsShimmer();
          }),

工資賬戶卡向用戶顯示資料

 class WageAccountsCard extends StatelessWidget {
   final String? date;
   final String? shiftName;
   final List<Wages>? wages;

  const WageAccountsCard(
      {Key? key,
       this.date,
       this.shiftName,
       this.wages})
       : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
       margin: const EdgeInsets.all(10),
       padding: const EdgeInsets.all(8),
       decoration: CustomBoxDecoration.cardDecoration(context, 
       shadow: true),
     child: Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
       children: [
      Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: [
          Text(
            shiftName ?? "",
            style: wageTextStyle,
          ),
          Text(
            date.toString(),
            style: wageTextStyle,
          ),
        ],
      ),
      SizedBox(
        height: Styles.height(context) * 0.01,
      ),
      Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: [
          Text(
            S.of(context).wage_type,
            style: cTextStyle,
          ),
          Text(
            S.of(context).balance,
            style: cTextStyle,
          ),
        ],
      ),
      const Divider(
        color: Colors.black,
      ),
      ListView.builder(
        itemBuilder: (context, index) {
          return Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              Text(
                wages![index].name!,
                style: cTextStyle,
              ),
              Text(
                wages![index].balance.toString(),
                style: cTextStyle,
              ),
            ],
          );
        },
        itemCount: wages!.length,
        shrinkWrap: true,
      ),
      SizedBox(
        height: Styles.height(context) * 0.01,
      ),
    ],
  ),
);

} }

uj5u.com熱心網友回復：

shiftName ?? "",用于在 null 情況下回傳默認值。

你得到空字串，因此你可以做

shiftName.isEmpty ? "onEmptyCaseValue" : shiftName

uj5u.com熱心網友回復：

return shiftName.isEmpty ? Center(child: Text('Empty')) : Text(
  shiftName ?? "",
  style: wageTextStyle,
),

uj5u.com熱心網友回復：

wageAccountsData[i].wages! 
         [i].shiftName!.isEmpty ? "":wageAccountsData[i].wages[i].shiftName,

插入這個就這樣寫

wageAccountsData[i].wages![i].shiftName ?? "Default Text",

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