formatFromString static method
通过字符串获得格式化的字符串
如果字符串不合法,返回null
Implementation
static String? formatFromString(String formattedString,
[String formatString = 'yyyy-MM-dd HH:mm:ss']) {
final dt = DateTime.tryParse(formattedString);
if (dt == null) return null;
return DateFormat(formatString, "zh_CN").format(dt);
}