Flutter Map 、List a-z 排序

字符串從 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;
 });