Flutter Map<String, dynamic> 、List<String> a-z 排序

字符串从 a-z 排序。

　　Map<String, String> map = XXX,

    List<String> keys = map.keys.toList();
    // key排序
    keys.sort((a, b) {
      List<int> al = a.codeUnits;
      List<int> bl = b.codeUnits;
      for (int i = 0; i < al.length; i++) {
        if (bl.length <= i) return 1;
        if (al[i] > bl[i]) {
          return 1;
        } else if (al[i] < bl[i]) return -1;
      }
      return 0;
    });