remove target, 古老的,
remove 一下 remove 完了,
[btn removeTarget:selfaction:@selector(delBlackList:) forControlEvents:UIControlEventTouchUpInside];
[btn addTarget:selfaction:@selector(joinBlacklist:) forControlEvents:UIControlEventTouchUpInside];
毫秒
[formatter setDateFormat:@"yyyyMMddHHmmssSSSS"];