未處理的異常：NoSuchMethodError：在 flutter 上的 null 上調用了方法“[]”

Question

我想在列表視圖中顯示數據，如下所示（那個是硬編碼的）

當我將其更改為列表時，出現此錯誤：

E/flutter ( 6925): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: NoSuchMethodError: The method '[]' was called on null.
E/flutter ( 6925): Receiver: null
E/flutter ( 6925): Tried calling: []("interest")

這是我的小部件構建：

@override
    Widget build(BuildContext context) {
      timeDilation = 2.0;
      return WillPopScope(
        onWillPop: () async => false,
        child: Scaffold(
          resizeToAvoidBottomInset: false,
          backgroundColor: kYellow,
          appBar: AppBar(
            leading: Hero(
              tag: 'animasilogo',
              child: Container(
                margin: EdgeInsets.all(5.0),
                child: Image.asset('assets/img/lemonlime.png'),
              ),
            ),
            title: Text('Simulator'),
            actions: [
              IconButton(
                icon: const Icon(Icons.exit_to_app),
                onPressed: () {
                  SharedPref.signOut();
                  Navigator.pushNamed(context, LoginScreen.id);
                },
              )
            ],
          ),
          body: RefreshIndicator(
            onRefresh: () => _fetchData(),
            child: loading
                ? Center(child: CircularProgressIndicator())
                : ListView.builder(
              itemCount: _loanmodel.length,
              itemBuilder: (context, i) {
              final data =_loanmodel[i];
              return Container(
                alignment: Alignment.topLeft,
                margin: const EdgeInsets.only(top: 15.0),
                  padding: EdgeInsets.all(20.0),
                child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: <Widget>[
                 Text("Interest :  " + data.interest , style: DefaultTextStyle.of(context).style.apply(fontSizeFactor: 1.5), textAlign: TextAlign.justify),
                  Text("Balance :  " + data.balance,  style: DefaultTextStyle.of(context).style.apply(fontSizeFactor: 1.5),textAlign: TextAlign.justify),
                  Text("Principal : " + data.principal,  style: DefaultTextStyle.of(context).style.apply(fontSizeFactor: 1.5),textAlign: TextAlign.justify),
                  Text("Installment :" + data.installment,  style: DefaultTextStyle.of(context).style.apply(fontSizeFactor: 1.5),textAlign: TextAlign.justify),
                  Divider(
                    color: Colors.black,
                  ),

                ],
              ),
                );
              },
            ),
          ),
        ),
      );
    }
  }

For API, Model and other function, you can check my another post in Unhandled Exception: type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'Iterable<dynamic>' flutter

Answer 1

確保您收到的部分數據不是 null。 應該收到“興趣”的部分是 null 並且因為它是您嘗試使用的數據的第一部分，所以其他部分也可能是 null