Question

我在从其他类的状态中调用函数时遇到问题。使用globalkey无效，也不能在各自的班级中设置孩子和父母。我正在使用最新版本的Flutter。

import 'package:flutter/material.dart';
import 'package:precisometrologia_app/globalslib.dart';
import 'package:precisometrologia_app/widgets/cert_idlogic.dart';

final certIDNumberState = new GlobalKey<CertIDNumberState>();
var certID = buildCertID();

class CertSubmitButton extends StatefulWidget {
  CertSubmitButton({this.formKey});

  var formKey;
  int _certCounter = 0;

  @override
  _CertSubmitButtonState createState() =>
      new _CertSubmitButtonState(formKey: formKey);
}

class _CertSubmitButtonState extends State<CertSubmitButton> {
  _CertSubmitButtonState({this.formKey});

  var formKey;

  void _increment() {
    setState(() {
      widget._certCounter++;
      certIncrementID = widget._certCounter;
      certID = buildCertID();
    });
  }

  @override
  Widget build(BuildContext context) {
    return Container(
        child: RaisedButton(
      color: Colors.green,
      shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(10.0)),
      onPressed: () {
        if (formKey.currentState.validate()) {
          Scaffold.of(context).showSnackBar(SnackBar(
            content: Text('Certificado Enviado'),
            backgroundColor: Colors.green,
          ));
          _increment();
          print(certID);
          CertIDNumber.of(context).updateState();
        }
      },
      child: Container(
          margin:
              EdgeInsets.only(left: 100.0, right: 100.0, top: 5.0, bottom: 5.0),
          child: Text(
            'Enviar Certificado',
            style: TextStyle(
              color: Colors.white,
            ),
          )),
    ));
  }
}

class CertIDNumber extends StatefulWidget {
  static CertIDNumberState of(BuildContext context) => context.ancestorStateOfType(const TypeMatcher<CertIDNumberState>());
  @override
  CertIDNumberState createState() =>
      new CertIDNumberState(key: certIDNumberState);
}

class CertIDNumberState extends State<CertIDNumber> {
  CertIDNumberState({key: Key});

  updateState() {
    if (this.mounted){
    setState(() {
      certID = buildCertID();
    });
    }
  }

  @override
  initState(){
    updateState();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
        margin:
            EdgeInsets.only(top: 10.0, bottom: 5.0, left: 10.0, right: 10.0),
        child: Column(children: <Widget>[
          Card(
              shape: BeveledRectangleBorder(),
              child: Container(
                margin: EdgeInsets.only(
                    bottom: 10.0, top: 10.0, left: 80.0, right: 80.0),
                child: Text(('Certificado: ') + certID.toString()),
              )),
          Divider(),
        ]));
  }
}

按下按钮后，调试控制台将返回此错误：

I / flutter（19413）：引发了另一个异常：NoSuchMethodError：方法'updateState'在null上调用。

我该怎么办？我在俯视什么吗？

在<states>内部始终在NULL上调用函数

0 个答案: