Detect if time format is in 12hr or 24hr format

问题

Is there any way to detect if the current device of the app uses 12h our 24h format, so that I can use one NSDateFormatter for 12h and one for 24h depending on the users language/loaction setting? Just Like the UIDatePicker detects and shows the AM/PM picker if it is 12h format.

回答1:

I figured it out, its pretty easy. I just added this code to viewDidLoad :

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]];
BOOL is24h = (amRange.location == NSNotFound && pmRange.location == NSNotFound);
[formatter release];
NSLog(@"%@\n",(is24h ? @"YES" : @"NO"));

And it perfectly returns YES or NO depending on the locale.

回答2:

And here is a Swift 3.0 updated version

func using12hClockFormat() -> Bool {

    let formatter = DateFormatter()
    formatter.locale = Locale.current
    formatter.dateStyle = .none
    formatter.timeStyle = .short

    let dateString = formatter.string(from: Date())
    let amRange = dateString.range(of: formatter.amSymbol)
    let pmRange = dateString.range(of: formatter.pmSymbol)

    return !(pmRange == nil && amRange == nil)
}

回答3:

this is swift solution that worked for me, those two above did not.

let dateString : String = DateFormatter.dateFormat(fromTemplate: "j", options: 0, locale: Locale.current)!

   if(dateString.contains("a")){
   // 12 h format
       return true
   }else{
   // 24 h format
       return false
   }

回答4:

Here is the Swift version:

func using12hClockFormat() -> Bool {

    let formatter = NSDateFormatter()
    formatter.locale = NSLocale.currentLocale()
    formatter.dateStyle = NSDateFormatterStyle.NoStyle
    formatter.timeStyle = NSDateFormatterStyle.ShortStyle

    let dateString = formatter.stringFromDate(NSDate())
    let amRange = dateString.rangeOfString(formatter.AMSymbol)
    let pmRange = dateString.rangeOfString(formatter.PMSymbol)

    return !(pmRange == nil && amRange == nil)
}

回答5:

Objective C category NSDate+Extensions:

@import Foundation;

@interface NSDate (Extensions)

- (NSString *)getTimeString;

@end


#import "NSDate+Extensions.h"

@implementation NSDate (Extensions)

- (NSString *)getTimeString
{
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    if ([self isTwelveHourDateFormat]) {
        [formatter setDateFormat:@"hh:mm\ndd MMM"];
    }
    else {
        [formatter setDateFormat:@"HH:mm\ndd MMM"];
    }
    return [formatter stringFromDate:self];
}

- (BOOL)isTwelveHourDateFormat
{
    NSString *dateFormat = [NSDateFormatter dateFormatFromTemplate:@"j" options:0 locale:[NSLocale currentLocale]];
    return [dateFormat containsString:@"a"];
}

@end

来源：https://stackoverflow.com/questions/7448360/detect-if-time-format-is-in-12hr-or-24hr-format

标签

objective-c

ios

cocoa-touch

nstimezone