非常晚，但是我用，

String title = "some string with no first letter caps";
    
title = title.replaceFirst(title[0], title[0].toUpperCase()); // Some string with no...

String? toCapitalize(String? input) {
  if (input == null || input.isEmpty) return input;
  return '${input[0].toUpperCase()}${input.substring(1).toLowerCase()}';
}

或扩展:

extension StringExtension on String {
  String? toCapitalize() {
    if (this == null || this.isEmpty) return this;
    return '${this[0].toUpperCase()}${this.substring(1).toLowerCase()}';
  }
}

奇怪的是，这是不可用的dart开始。下面是一个扩展的大写字符串:

extension StringExtension on String {
  String capitalized() {
    if (this.isEmpty) return this;
    return this[0].toUpperCase() + this.substring(1);
  }
}

它首先检查String是否为空，然后将第一个字母大写，并将其余字母相加

用法:

import "path/to/extension/string_extension_file_name.dart";

var capitalizedString = '${'alexander'.capitalized()} ${'hamilton, my name is'.capitalized()} ${'alexander'.capitalized()} ${'hamilton'.capitalized()}');
// Print result: "Alexander Hamilton, my name is Alexander Hamilton"

String fullNameString =
    txtControllerName.value.text.trim().substring(0, 1).toUpperCase() +
        txtControllerName.value.text.trim().substring(1).toLowerCase();

我使用了不同的实现:

创建一个类:

import 'package:flutter/services.dart';

class FirstLetterTextFormatter extends TextInputFormatter {
  @override
  TextEditingValue formatEditUpdate(
      TextEditingValue oldValue, TextEditingValue newValue) {
    return TextEditingValue(
      //text: newValue.text?.toUpperCase(),
      text: normaliseName(newValue.text),
      selection: newValue.selection,
    );
  }

  /// Fixes name cases; Capitalizes Each Word.
  String normaliseName(String name) {
    final stringBuffer = StringBuffer();

    var capitalizeNext = true;
    for (final letter in name.toLowerCase().codeUnits) {
      // UTF-16: A-Z => 65-90, a-z => 97-122.
      if (capitalizeNext && letter >= 97 && letter <= 122) {
        stringBuffer.writeCharCode(letter - 32);
        capitalizeNext = false;
      } else {
        // UTF-16: 32 == space, 46 == period
        if (letter == 32 || letter == 46) capitalizeNext = true;
        stringBuffer.writeCharCode(letter);
      }
    }

    return stringBuffer.toString();
  }
}

然后你导入类到任何页面，你需要例如在TextField的inputFormatters属性，只是调用上面的小部件:

TextField(
inputformatters: [FirstLetterTextFormatter()]),
),

下面是代码，如果你想在一个句子中大写每个单词，例如，如果你想大写你客户的fullName的每个部分，你可以简单地在你的模型类中使用以下扩展:

extension StringExtension on String {
  String capitalizeFirstLetter() {
    return "${this[0].toUpperCase()}${this.substring(1).toLowerCase()}";
  }
}

只需使用这个getter

String get formalFullName =>  fullName.capitalizeFirstLetter().splitMapJoin(RegExp(r' '),
                onNonMatch: (str) => str.toString().capitalize());

希望这对大家有所帮助