TextInputFormatter class Null safety

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:

Implementers

Constructors

TextInputFormatter()

Properties

hashCode int
The hash code for this object. [...]
read-only, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited

Methods

formatEditUpdate(TextEditingValue oldValue, TextEditingValue newValue) TextEditingValue
Called when text is being typed or cut/copy/pasted in the EditableText. [...]
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
inherited
toString() String
A string representation of this object. [...]
inherited

Operators

operator ==(Object other) bool
The equality operator. [...]
inherited

Static Methods

withFunction(TextInputFormatFunction formatFunction) TextInputFormatter
A shorthand to creating a custom TextInputFormatter which formats incoming text input changes with the given function.