backspace method

void backspace()

Implementation

void backspace() {
  final beforeString = text.substring(0, selection.start);
  final afterString = text.substring(selection.end);

  // 删除前一个字符
  if (selection.isCollapsed) {
    final backspaced = beforeString.characters.skipLast(1);
    text = backspaced.string + afterString;
    selection = TextSelection.collapsed(offset: backspaced.string.length);
  }
  // 删除选中的部分
  else if (selection.isNormalized) {
    text = beforeString + afterString;
    selection = TextSelection.collapsed(offset: beforeString.length);
  }
}