如何在 listviewbuilder 的 textformfield 中添加验证？

Question

I am creating a dynamic textformfield using Listviewbuilder :-

(1). I want to add validation in mobile field (2). I want to add validation in name field

But in dynamic condition my validation is not working properly.

Answer 1

First store your fields validation in a Map like below.

Map contains 'key' as fields name and 'values' as validator functions.

 Map<String, String? Function(String?)?> formFields = { 'username': (String? value) { return (value!.isEmpty) ? 'Can not be Empty' : null; }, 'password': (String? value) { return (value == null || value!.length < 8) ? 'Must be 8 Char Long' : null; }, };

Use the Map key to access validator functions.

formFields[formFields.keys.elementAt(index)]

And then use ListView.builder to generate multiple TextFormFields like below.

 ListView.builder( itemCount: formFields.length, itemBuilder: (context, index) { return TextFormField( decoration: InputDecoration( labelText: formFields.keys.elementAt( index), // this gives key String ('username', 'password') ), onSaved: (String? value) {}, validator: formFields[formFields.keys.elementAt(index)], ); }, ),

For different type of Form Elements lets say TextFormField, DropdownButtonFormField you could directly add these widgets on the MAP instead of Validator only.

 Map<String, String? Function(String?)?> formFields = { 'username': TextFormField( decoration: InputDecoration( labelText: formFields.keys.elementAt( index), // this gives key String ('username', 'password') ), onSaved: (String? value) {}, validator: TextFormField( decoration: InputDecoration( labelText: formFields.keys.elementAt( index), // this gives key String ('username', 'password') ), onSaved: (String? value) {}, validator: (String? value) { return (value!.isEmpty) ? 'Can not be Empty' : null; }, );, );, );