Find if user prefers 12 / 24 Hour Clock?

问题:

I've got a drawRect that makes a timeline a bit like iCal. I use a for loop to write the times along a scroll view. I was wondering if A) theres a way of determining whether the user has chosen a 12 or 24 hour clock in the system settings and B) if there is a more efficient way of changing the time labels then calling an 'if' query every pass of the 'for' loop. Cheers

回答1:

NSDate *today = [NSDate date];
NSString *formattedString = [NSDateFormatter localizedStringFromDate:today dateStyle: kCFDateFormatterNoStyle timeStyle: kCFDateFormatterShortStyle];

NSRange foundRange;
foundRange = [formattedString rangeOfString:"am" options:NSCaseInsensitiveSearch];
if(foundRange.location == NSNotFound) {
    foundRange = [formattedString rangeOfString:"pm" options:NSCaseInsensitiveSearch];
}

BOOL isAMPMSettingOn = (foundRange.location != NSNotFound);

回答2:

The earlier answers assume that the "AM" and "PM" symbols are represented in roman characters. This code adapted from keyur bhalodiya does a better job at handling languages like Chinese, by using the AMSymbol and PMSymbol methods of NSDateFormatter.

-(BOOL)uses24hourTime
{
     NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
     [formatter setLocale:[NSLocale currentLocale]];
     [formatter setDateStyle:NSDateFormatterNoStyle];
     [formatter setTimeStyle:NSDateFormatterShortStyle];

     NSString *dateString = [formatter stringFromDate:[NSDate date]];
     NSRange amRange = [dateString rangeOfString:[formatter AMSymbol]];
     NSRange pmRange = [dateString rangeOfString:[formatter PMSymbol]];

     return (amRange.location == NSNotFound && pmRange.location == NSNotFound);
}

回答3:

NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
[dateFormatter setDateStyle:NSDateFormatterNoStyle];
[dateFormatter setTimeStyle:NSDateFormatterLongStyle];

if([[dateFormatter dateFormat] rangeOfString:@"a"].location != NSNotFound) {
    // user prefers 12 hour clock
} else {
    // user prefers 24 hour clock
}