Question

''''我是Flutter的初学者，这是问题所在-我试图用验证和'Submit'按钮构建表单，该表单必须控制文本字段，但是发生了异常。 NoSuchMethodError（NoSuchMethodError：方法'validate'在null上调用。接收者：null 尝试调用：validate（））。这是代码：“''

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:fluttertoast/fluttertoast.dart';

class SharedKonusu extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => ShareState();
}

class ShareState extends State<SharedKonusu> {
  final isimCtrl = TextEditingController();
  final soyisimCtrl = TextEditingController();
  final globalCtrl = GlobalKey<FormState>();

  String isimStr = "";
  String soyisimStr = "";
  bool kayitDurum = false;
  int kayitNo = 0;

  @override
  void dispose() {
    isimCtrl.dispose();
    soyisimCtrl.dispose();
    super.dispose();
  }

  void kayitYap(String gIsim, String gSisim) async {
    final registeR = await SharedPreferences.getInstance();

    if (globalCtrl.currentState.validate()) {
      registeR.setBool("durum", true);
      registeR.setInt("kayitNo", 1);
      registeR.setString("isim", gIsim);
      registeR.setString("soyisim", gSisim);

      Fluttertoast.showToast(
          msg: "Registering...",
          toastLength: Toast.LENGTH_LONG,
          gravity: ToastGravity.BOTTOM);
    }
  }

  void getData() async {
    final registeR = await SharedPreferences.getInstance();

    bool kDurum = registeR.getBool("durum");
    int kNo = registeR.getInt("kayitNo");
    String kIsim = registeR.getString("isim");
    String kSisim = registeR.getString("soyisim");

    setState(() {
      kayitDurum = kDurum;
      kayitNo = kNo;
      isimStr = kIsim;
      soyisimStr = kSisim;
    });
    Fluttertoast.showToast(
      msg: "Getting data...",
      toastLength: Toast.LENGTH_LONG,
      gravity: ToastGravity.BOTTOM,
    );
  }

  void deleteData() async {
    final registeR = await SharedPreferences.getInstance();
    registeR.remove("isim");
    registeR.remove("soysisim");
    registeR.remove("ksyitNo");
    registeR.remove("durum");
    Fluttertoast.showToast(
      msg: "Getting data...",
      toastLength: Toast.LENGTH_LONG,
      gravity: ToastGravity.BOTTOM,
    );
  }

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      appBar: AppBar(
        title: Text("My Title"),
      ),
      body: Form(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            TextFormField(
              validator: (deger) {
                if (deger.isEmpty) {
                  return "Incorrect Name";
                }
              },
              controller: isimCtrl,
              decoration: InputDecoration(hintText: "Your Name"),
            ),
            TextFormField(
              validator: (sname) {
                if (sname.isEmpty) {
                  return "Incorrect Surname";
                }
              },
              controller: soyisimCtrl,
              decoration: InputDecoration(
                hintText: "Your surname",
              ),
            ),
            Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Expanded(
                  child: Padding(
                    padding: EdgeInsets.all(20.0),
                    child: RaisedButton(
                      onPressed: () =>
                          kayitYap(isimCtrl.text, soyisimCtrl.text),
                      shape: RoundedRectangleBorder(
                        borderRadius: new BorderRadius.circular(50.0),
                      ),
                      color: Colors.blue,
                      child: Text(
                        "Register",
                        style: TextStyle(color: Colors.white),
                      ),
                    ),
                  ),
                ),
                Expanded(
                  child: Padding(
                    padding: EdgeInsets.all(20.0),
                    child: RaisedButton(
                      onPressed: () => getData(),
                      shape: RoundedRectangleBorder(
                        borderRadius: new BorderRadius.circular(50.0),
                      ),
                      color: Colors.green,
                      child: Text(
                        "Get data",
                        style: TextStyle(color: Colors.white),
                      ),
                    ),
                  ),
                ),
                Expanded(
                  child: Padding(
                    padding: EdgeInsets.all(20.0),
                    child: RaisedButton(
                      onPressed: () => deleteData(),
                      shape: RoundedRectangleBorder(
                        borderRadius: new BorderRadius.circular(50.0),
                      ),
                      color: Colors.red,
                      child: Text(
                        "Delete data",
                        style: TextStyle(color: Colors.white),
                      ),
                    ),
                  ),
                ),
              ],
            ),
            Expanded(
              child: Padding(
                padding: EdgeInsets.all(20.0),
                child: Column(
                  children: <Widget>[
                    Text("Name: $isimStr"),
                    Text("Surname:$soyisimStr"),
                    Text("Registered:$kayitDurum"),
                    Text("Register No: $kayitNo"),
                  ],
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

Answer 1

这是因为您没有将formKey globalCtrl分配给Form小部件的键参数。

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:fluttertoast/fluttertoast.dart';

class SharedKonusu extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => ShareState();
}

class ShareState extends State<SharedKonusu> {
  final isimCtrl = TextEditingController();
  final soyisimCtrl = TextEditingController();
  final globalCtrl = GlobalKey<FormState>();

  String isimStr = "";
  String soyisimStr = "";
  bool kayitDurum = false;
  int kayitNo = 0;

  @override
  void dispose() {
    isimCtrl.dispose();
    soyisimCtrl.dispose();
    super.dispose();
  }

  void kayitYap(String gIsim, String gSisim) async {
    final registeR = await SharedPreferences.getInstance();

    if (globalCtrl.currentState.validate()) {
      registeR.setBool("durum", true);
      registeR.setInt("kayitNo", 1);
      registeR.setString("isim", gIsim);
      registeR.setString("soyisim", gSisim);

      Fluttertoast.showToast(
          msg: "Registering...",
          toastLength: Toast.LENGTH_LONG,
          gravity: ToastGravity.BOTTOM);
    }
  }

  void getData() async {
    final registeR = await SharedPreferences.getInstance();

    bool kDurum = registeR.getBool("durum");
    int kNo = registeR.getInt("kayitNo");
    String kIsim = registeR.getString("isim");
    String kSisim = registeR.getString("soyisim");

    setState(() {
      kayitDurum = kDurum;
      kayitNo = kNo;
      isimStr = kIsim;
      soyisimStr = kSisim;
    });
    Fluttertoast.showToast(
      msg: "Getting data...",
      toastLength: Toast.LENGTH_LONG,
      gravity: ToastGravity.BOTTOM,
    );
  }

  void deleteData() async {
    final registeR = await SharedPreferences.getInstance();
    registeR.remove("isim");
    registeR.remove("soysisim");
    registeR.remove("ksyitNo");
    registeR.remove("durum");
    Fluttertoast.showToast(
      msg: "Getting data...",
      toastLength: Toast.LENGTH_LONG,
      gravity: ToastGravity.BOTTOM,
    );
  }

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      appBar: AppBar(
        title: Text("My Title"),
      ),
      body: Form(
        key: globalCtrl,
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            TextFormField(
              validator: (deger) {
                if (deger.isEmpty) {
                  return "Incorrect Name";
                }
              },
              controller: isimCtrl,
              decoration: InputDecoration(hintText: "Your Name"),
            ),
            TextFormField(
              validator: (sname) {
                if (sname.isEmpty) {
                  return "Incorrect Surname";
                }
              },
              controller: soyisimCtrl,
              decoration: InputDecoration(
                hintText: "Your surname",
              ),
            ),
            Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Expanded(
                  child: Padding(
                    padding: EdgeInsets.all(20.0),
                    child: RaisedButton(
                      onPressed: () =>
                          kayitYap(isimCtrl.text, soyisimCtrl.text),
                      shape: RoundedRectangleBorder(
                        borderRadius: new BorderRadius.circular(50.0),
                      ),
                      color: Colors.blue,
                      child: Text(
                        "Register",
                        style: TextStyle(color: Colors.white),
                      ),
                    ),
                  ),
                ),
                Expanded(
                  child: Padding(
                    padding: EdgeInsets.all(20.0),
                    child: RaisedButton(
                      onPressed: () => getData(),
                      shape: RoundedRectangleBorder(
                        borderRadius: new BorderRadius.circular(50.0),
                      ),
                      color: Colors.green,
                      child: Text(
                        "Get data",
                        style: TextStyle(color: Colors.white),
                      ),
                    ),
                  ),
                ),
                Expanded(
                  child: Padding(
                    padding: EdgeInsets.all(20.0),
                    child: RaisedButton(
                      onPressed: () => deleteData(),
                      shape: RoundedRectangleBorder(
                        borderRadius: new BorderRadius.circular(50.0),
                      ),
                      color: Colors.red,
                      child: Text(
                        "Delete data",
                        style: TextStyle(color: Colors.white),
                      ),
                    ),
                  ),
                ),
              ],
            ),
            Expanded(
              child: Padding(
                padding: EdgeInsets.all(20.0),
                child: Column(
                  children: <Widget>[
                    Text("Name: $isimStr"),
                    Text("Surname:$soyisimStr"),
                    Text("Registered:$kayitDurum"),
                    Text("Register No: $kayitNo"),
                  ],
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

发生异常NoSuchMethodError Flutter验证错误

1 个答案: