Question

大家好我有一个模态类文件，名为：orderdetails.dart，这是代码：

class OrderDetails {
  final shipmentNumber = "26";
}

我需要将ShipmentNumber数据作为文本传递给下面的小部件，

class MainPage extends StatefulWidget {
  final OrderDetails orderDetails;

  const MainPage({Key key, this.orderDetails}) : super(key: key);


  @override
  _MainPageState createState() => _MainPageState();
}

class _MainPageState extends State<MainPage> {
  OrderDetails orderDetails;

  @override
  void initState() {
    super.initState();

    // setState is not needed in initState
    orderDetails = OrderDetails();
  }

  @override
  Widget build(BuildContext context) {

       
        Container(
          height: 1000,
          child: ListView.builder(
            itemCount: int.parse(widget.orderDetails.shipmentNumber),
            shrinkWrap: true,
            itemBuilder: (ctx, int) {
              return Card(
                color: Color(0xFF1f2032),
                elevation: 15,
                child: Container(
                  width: 60,
                  height: 60,
                  child: Row(
                    mainAxisAlignment: MainAxisAlignment.spaceAround,
                    children: <Widget>[
                      Text(
                        widget.orderDetails.shipmentNumber,
                        style: TextStyle(color: Colors.lightGreenAccent),
                      ),
                      Card(
                        color: Color(0xfffeaf0d),
                        child: Container(
                            height: 40,
                            width: 40,
                            child: Icon(
                              Icons.local_shipping,
                              color: Colors.white,
                              size: 25,
                            )),
                      ),

，但它返回NotSuchMethodError，在Null上调用了吸气剂shipmentNumber 有没有办法从该文件中调用此方法？

Answer 1

您使用的widget.orderDetails.shipmentNumber为空，您正在使用orderDetails = OrderDetails();设置状态字段

尝试this.orderDetails.shipmentNumber或将此字段添加到构造函数中

Answer 2

在调用 MainPage 类构造函数时，只需将"engines": {"yarn": "x.x"},作为OrderDetails()参数的参数，并从 _MainPageState 类中删除orderDetails字段

这就是您应该调用 MainPage 类构造函数的方式。

orderDetails

无法在振颤中从模态类传递数据

2 个答案: