numeric_formatter library Null safety


An implementation of NumberInputFormatter that converts a numeric input to credit card number form (4-digit grouping). For example, a input of 12345678 should be formatted to 1234 5678.
An abstract class extends from TextInputFormatter and does numeric filter. It has an abstract method _format() that lets its children override it to format input displayed on TextField
An implementation of NumberInputFormatter automatically inserts thousands separators to numeric input. For example, a input of 1234 should be formatted to 1,234.