Converting negative number in the string format to double

Question

When i use double.parse on my textfield input i get the following error FormatException (FormatException: Invalid double -). Saw a similar post but problem doesn't seem to be solve

Also how can i prevent user from entering two "." and "-" . Any help is much appreciated. Ty for your time

 TextFormField(
          inputFormatters: [FilteringTextInputFormatter.allow(RegExp(r'^-?\d*.?\d*')),],
          keyboardType: TextInputType.numberWithOptions(signed: true,decimal: true),

          onChanged:(value) {
            setState(() {
              data = double.parse(value);
            });
          },
          decoration: InputDecoration(
            border: OutlineInputBorder(),
            labelText: 'data'
          ),

        ),

I tried using RegExp('[0-9.-]') but it doesn't work as well. I still get back the same error message as stated above

Answer 1

double.parse is expecting a double as string. So when you enter a dot (.) or a dash (-) and it tries to parse it as a double, it throws an exception. You need to apply some checks in order to solve this.

Try this

TextFormField(
      inputFormatters: [
        FilteringTextInputFormatter.allow(RegExp(r'^-?\d*.?\d*')),
      ],
      keyboardType:
          TextInputType.numberWithOptions(signed: true, decimal: true),
      onChanged: (value) {
        if (value.isNotEmpty && value != '.' && value != '-') {
          setState(() {
            data = double.parse(value);
          });
        }
      },
      decoration:
          InputDecoration(border: OutlineInputBorder(), labelText: 'data'),
    ),