im trying to make a calculator app and I'm trying to set some validation messages for the text fields like "please enetr numbers only" I used formkey to do that but the validation is not working I'm new to dart I couldn't figure what is the issue

this is my code :

    final formkey = GlobalKey<FormState>();
  @override
  Widget build(BuildContext context) {
    return Container(
        padding: new EdgeInsets.all(25.0),
        child: Form(
          key: formkey,
          child: Column(
            children: <Widget>[
              SizedBox(height: 45),
              Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
                  const Text(
                    "Basic Calculator",
                    style: TextStyle(fontWeight: FontWeight.bold, fontSize: 30),
                  )
                ],
              ),
              SizedBox(height: 60),
              Row(
                children: <Widget>[
                  const Text(
                    "First Number",
                    style: TextStyle(fontWeight: FontWeight.bold),
                  )
                ],
              ),
              SizedBox(height: 10),
              Row(
                children: <Widget>[
                  new Flexible(
                    child: new TextFormField(
                      keyboardType: TextInputType.number,
                      controller: num1controller,
                      decoration: InputDecoration(
                        hintText: "Enter a number",
                        border: new OutlineInputBorder(
                            borderSide: new BorderSide(color: Colors.teal)),
                      ),
                      validator: (value) {
                        if (value!.isEmpty ||
                            !RegExp(r'^[,]*[.][0-9] $').hasMatch(value!)) {
                          return "please enter  numbers only";
                        } else {
                          return null;
                        }
                      },
                    ),
                  ),
                ],
              )

CodePudding user response：

The given code looks fine to me, however, you are missing one thing. You need to call the validate() method on the currentState of the form. Like this formKey.currentState.validate(). This is needed to be called in order to validate the form.

Alternatively, you can also use autovalidateMode property of the form field (Not tested though). Like: autovalidateMode: AutovalidateMode.onUserInteraction. This way you won't need to call the validate method on the form state.