iOS:从字符串切换12/24小时

Question

有趣的问题让我感到震惊.

我收到从服务器到设备的字符串时间.然后我将其转换为NSDate.当设备设置为24小时显示时,生活是美好的.

现在我在设置为12小时的设备上测试它.一切都停止了.日期将返回null

我第一次

 NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
 [dateFormat setDateFormat:@"HH:mm"];
 self.startTime = [dateFormat dateFromString:(NSString *)self.startTime];

适用于显示24小时但不是12小时的设备.

然后我试过了

 NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
 [dateFormat setDateFormat:@"hh:mm"];
 self.startTime = [dateFormat dateFromString:(NSString *)self.startTime];

这工作正常到中午12点,然后所有日期都返回为null

更新

我也试过添加"a"但这仍然导致返回null

 if (startDate == nil)
 {
      NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
      [dateFormat setDateFormat:@"hh:mm a"];
      startDate = [dateFormat dateFromString:(NSString *)self.startTime];
 }

更新2

添加本地,添加:添加全部的ss仍然无法正常工作

NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
NSLocale *twelveHourLocale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"];
dateFormat.locale = twelveHourLocale;
[dateFormat setDateFormat:@"hh:mm a"];
startDate = [dateFormat dateFromString:(NSString *)self.startTime];

Answer 1

它很接近......我认为你需要:

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"];
[dateFormatter setLocale:locale];
[dateFormatter setDateFormat:@"HH:mm"];
startDate = [dateFormatter dateFromString:(NSString *)self.startTime];

Answer 2

你可以试试这个

    12 to 24 hour format


    NSDateFormatter* df = [[NSDateFormatter alloc] init];
    [df setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"]];
    [df setTimeZone:[NSTimeZone systemTimeZone]];
    [df setDateFormat:@"hh:mm a"];
    NSDate* newDate = [df dateFromString:LocationTrackingStartTime];
    [df setDateFormat:@"HH:mm"];
    newDate = [df stringFromDate:newDate];

   24 to 12 hour format

    NSDateFormatter* df = [[NSDateFormatter alloc] init];
    [df setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US"]];
    [df setTimeZone:[NSTimeZone systemTimeZone]];
    [df setDateFormat:@"yyyy-mm-dd hh:mm:ss"];
    NSDate* newDate = [df dateFromString:[df stringFromDate:[NSDate date]]];
    [df setDateFormat:@"hh:mm a"];
    newDate = [df stringFromDate:[NSDate date]];