formatEditUpdate method

@override TextEditingValue formatEditUpdate(TextEditingValue oldValue, TextEditingValue newValue)

Called when text is being typed or cut/copy/pasted in the EditableText.

You can override the resulting text based on the previous text value and the incoming new text value.

When formatters are chained, oldValue reflects the initial value of TextEditingValue at the beginning of the chain.

Implementation

@override
TextEditingValue formatEditUpdate(
    TextEditingValue oldValue, TextEditingValue newValue) {
  const String pointer = '.';

  /// 输入完全删除
  if (newValue.text.isEmpty) return const TextEditingValue();

  /// 只允许输入数字和小数点
  if (!exp.hasMatch(newValue.text)) return oldValue;

  /// 包含小数点的情况
  if (newValue.text.contains(pointer)) {
    /// 精度为0，即不含小数
    if (decimalLength == 0) return oldValue;

    /// 包含多个小数
    if (newValue.text.indexOf(pointer) !=
        newValue.text.lastIndexOf(pointer)) {
      return oldValue;
    }

    final String input = newValue.text;
    final int index = input.indexOf(pointer);

    /// 小数点前位数
    final int lengthBeforePointer = input.substring(0, index).length;

    /// 整数部分大于约定长度
    if (lengthBeforePointer > numberLength) return oldValue;

    /// 小数点后位数
    final int lengthAfterPointer =
        input.substring(index, input.length).length - 1;

    /// 小数位大于精度
    if (lengthAfterPointer > decimalLength) return oldValue;
  } else if (

      /// 以点开头
      newValue.text.startsWith(pointer) ||

          /// 如果第1位为0，并且长度大于1，排除00,01-09所有非法输入
          (newValue.text.startsWith('0') && newValue.text.length > 1) ||

          /// 如果整数长度超过约定长度
          newValue.text.length > numberLength) {
    return oldValue;
  }
  return newValue;
}