Xcode倒数计时器不倒计时（NSCalender）

Question

我正在创建一个简单的IOS应用程序将倒数计时器。当我在模拟器中运行应用程序时，倒数计时器不会倒计时。它只停留在当前时间。

关于使数字排成一行的任何建议都会很好。

我的.h文件

//  ViewController.h
//  ******    
//
//  Created by ***** on 7/29/12.
//  Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//
#import <UIKit/UIKit.h>

@interface ViewController : UIViewController {

    NSDate *destinationDate;

    IBOutlet UILabel *datelabel;

    NSTimer *timer;

}




@end

我的.m文件

//
//  ViewController.m
//  ******
//
//  Created by ******* on 7/29/12.
//  Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//

#import "ViewController.h"

@implementation ViewController

-(void) updateLabel {

    NSCalendar *calender = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    int units = NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
    NSDateComponents *components = [calender components:units fromDate:[NSDate date] toDate:destinationDate options:0];
    [datelabel setText:[NSString stringWithFormat:@"%d%c %d%c %d%c %d%c", [components day], ' ', [components hour], ' ', [components minute], ' ', [components second], ' ']];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Release any cached data, images, etc that aren't in use.
}

#pragma mark - View lifecycle

- (void)viewDidLoad
{
    [super viewDidLoad];

    destinationDate = [[NSDate dateWithTimeIntervalSince1970:1343609103] retain];
    timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(updateLabel) userInfo:nil repeats:NO];

    // Do any additional setup after loading the view, typically from a nib.
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
}

- (void)viewDidDisappear:(BOOL)animated
{
    [super viewDidDisappear:animated];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    // Return YES for supported orientations
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

@end

Answer 1

将重复YES设置为您的计时器。

[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(updateLabel) userInfo:nil repeats:YES];

编辑：还可以考虑使用NSDateFormatter来显示字符串。

如果您想改进布局，我建议将NSDateFormatter与多个UILabel结合使用。日期格式化程序可用于创建所需格式的字符串，每个标签可以保存日期/时间字符串的特定部分。看一下Apple's Data Formatting Guide最低调的部分是Unicode Technical Standard #35的链接，它定义了您可以使用的所有格式。

分割完日期后，您只需按照自己的意愿布置视图即可。