inputFormatters property
e.g.
inputFormatters: <TextInputFormatter>[
FilteringTextInputFormatter.digitsOnly, // Allow only digits
FilteringTextInputFormatter.allow(RegExp(r'^\d+\.?\d{0,2}$')), // Allow digits and at most 2 decimal places
FilteringTextInputFormatter.allow(RegExp(r'[a-zA-Z]')), // Allow alphabets only
FilteringTextInputFormatter.allow(RegExp(r'[a-zA-Z0-9!@#$%^&*()_+,\-=\[\]{};':"\\|<>\?]+')), // Allow alphanumeric and special characters
...
...
],
Implementation
final List<TextInputFormatter>? inputFormatters;