Dart APIunself_componentTextAreaonTap onTap property Null safety GestureTapCallback? onTap final Implementation final GestureTapCallback? onTap; unself_component unself_component TextArea onTap property TextArea class Constructors TextArea Properties autofocus controller hashCode key onChanged onTap runtimeType Methods build createElement debugDescribeChildren debugFillProperties noSuchMethod toDiagnosticsNode toString toStringDeep toStringShallow toStringShort Operators operator ==