Checkbox form validation

Question

How can I validate a checkbox in a Flutter Form? Every other validation works fine, but the checkbox doesn\'t show an Error. Here is my code:

FormFi         


        

Answer 1

in case if you want to put your checkbox directly in your Form widget tree you can use solution provided below with FormField widget. Instead of using ListTile I used rows and columns as my form was requiring different layout.

FormField(
  builder: (state) {
    return Column(
      children: [
        Row(
          children: [
            Checkbox(
              value: checkboxValue,
              onChanged: (value) {
                setState(() {
//save checkbox value to variable that store terms and notify form that state changed
                  checkboxValue = value;
                  state.didChange(value);
                });
              }),
            Text('I accept terms'),
          ],
        ),
//display error in matching theme
        Text(
          state.errorText ?? '',
          style: TextStyle(
            color: Theme.of(context).errorColor,
          ),
        )
      ],
    );
  },
//output from validation will be displayed in state.errorText (above)
  validator: (value) {
    if (!checkboxValue) {
      return 'You need to accept terms';
    } else {
      return null;
    }
  },
),