谁能向我解释为什么以下代码返回不一致的时间值?尝试从用户指定的日期/时间字符串创建 NSDate 对象时,我得到了不正确的结果,我将下面的代码放在一起来说明问题。
// Create two strings containing the current date and time
NSDateFormatter * dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:@"yyyy-MM-dd"];
NSDateFormatter * timeFormat = [[NSDateFormatter alloc] init];
[timeFormat setDateFormat:@"HH:mm:ss a"];
timeFormat.AMSymbol = @"AM";
timeFormat.PMSymbol = @"PM";
timeFormat.timeZone = [NSTimeZone timeZoneWithAbbreviation:@"EDT"];
NSDate * now = [[NSDate alloc] init];
NSString *theDate = [dateFormat stringFromDate:now];
NSString *theTime = [timeFormat stringFromDate:now];
NSLog(@"The current date/time is (GTM): %@", now);
NSLog(@"The current date/time is (EDT): %@ %@", theDate, theTime);
// Combine the date and time strings
NSMutableString * theDateTime = [[NSMutableString alloc] init];
theDateTime = [theDateTime stringByAppendingString:theDate];
theDateTime = [theDateTime stringByAppendingString:@" "];
theDateTime = [theDateTime stringByAppendingString:theTime];
// Define the formatter to parse the combined date and time string
NSDateFormatter * dateFormatter=[[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss a"];
dateFormatter.AMSymbol = @"AM";
dateFormatter.PMSymbol = @"PM";
dateFormatter.timeZone = [NSTimeZone timeZoneWithAbbreviation:@"EDT"];
// Create an NSDate object using the combined date and time string
NSDate * theDateTimeObject=[dateFormatter dateFromString:theDateTime];
NSString * theDateTimeString=[dateFormatter stringFromDate:theDateTimeObject];
// Print the results
NSLog(@"theDateTimeObject (GMT) = %@", theDateTimeObject);
NSLog(@"theDateTimeString (EDT) = %@", theDateTimeString);
此代码产生以下输出:
The current date/time is (GMT): 2015-09-29 22:28:10 +0000
The current date/time is (EDT): 2015-09-29 18:28:10 PM
theDateTimeObject (GMT) = 2015-09-29 16:28:10 +0000
theDateTimeString (EDT) = 2015-09-29 12:28:10 PM
显然,当日期格式化程序解析组合的日期和时间字符串以创建 NSDate 对象时,出现了问题。它似乎不理解输入时区,并返回一个比它应该是几个小时的 GMT 时间(即 +4 小时)。我已将时区设置为“EDT”,所以不确定我还能做些什么来解决这个问题,除了硬编码输入中的偏移量,我宁愿不这样做。任何帮助,将不胜感激。