Question

我试图在模型中分配输入值，以便在API POST请求中使用它。但是，我不断收到错误消息：

setter was called on null when saving

型号：

@JsonSerializable()
class Discount {
  String value;

  Discount();

  set setValue(String value) { 
    this.value = value; 
  }

Dart代码：

                children: <Widget>[
                    Expanded(
                      child: Container(
                        margin: EdgeInsets.only(right: 5),
                        child: TextFormField(
                          initialValue: _invoiceFormData.discount?.value ?? '0.00',
                          inputFormatters: [_amountValidator],
                          keyboardType: TextInputType.numberWithOptions(
                            decimal: true,
                            signed: false,
                          ),
                          decoration: TextFormField.decoration(
                            labelText: Localizations.of(context)
                                .text('label_invoice_discount'),
                          ),
                          onChanged: (String value) {
                            setState(() {
                              discountTotal = value;
                        });   
                        },
                         onSaved: (value) => _invoiceFormData
                  .discount.setValue = value,
                        ),
                      ),
                    ),
                    FlatButton(
                        onPressed: () {
                          setState(() {
                          discountType = !discountType;
                          });
                        },                        
                     ),
                  ],

日志：

The setter 'setValue=' was called on null.
Receiver: null
Tried calling: setValue="10.00"

我尝试设置_invoiceFormData.discount.value = value，但仍显示相同的错误。

Answer 1

使用StatefulWidget类和

更改此

onSaved: (value) => _invoiceFormData
          .discount.setValue = value,

到

onSaved: (value) => setState(() {
      onSaved: (value) => _invoiceFormData
          .discount.setValue = value,
    });

Answer 2

当您使用设置器_invoiceFormData.discount时，您的日志说setValue=为空。

要解决此问题，您首先需要在名为discount的对象中实例化字段_invoiceFormData。例如，当您初始化此表单数据（也许在initState（）中）时，应执行_invoiceFormData.discount = Discount();，然后它将不再为null

setter'setValue ='在null上被调用

2 个答案: