TextInputFormatter class abstract

A TextInputFormatter can be optionally injected into an EditableText to provide as-you-type validation and formatting of the text being edited.

Text modification should only be applied when text is being committed by the IME and not on text under composition (i.e., only when TextEditingValue.composing is collapsed).

See also the FilteringTextInputFormatter, a subclass that removes characters that the user tries to enter if they do, or do not, match a given pattern (as applicable).

To create custom formatters, extend the TextInputFormatter class and implement the formatEditUpdate method.

Handling emojis and other complex characters

It's important to always use characters when dealing with user input text that may contain complex characters. This will ensure that extended grapheme clusters and surrogate pairs are treated as single characters, as they appear to the user.

For example, when finding the length of some user input, use string.characters.length. Do NOT use string.length or even string.runes.length. For the complex character "👨‍👩‍👦", this appears to the user as a single character, and string.characters.length intuitively returns 1. On the other hand, string.length returns 8, and string.runes.length returns 5!

See also:

• EditableText on which the formatting apply.
• FilteringTextInputFormatter, a provided formatter for filtering characters.