先看下效果（请忽略图片的丑陋）
钟.gif
这个demo很简单，主要有三点比较重要：
1.根据当前时间计算时分秒偏转角度，并且处理旋转的动画，很简单的一个旋转动画transform
- (void)tick{
// NSCalendarIdentifierGregorian : 指定日历的算法
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
// NSDateComponents封装了日期的组件,年月日时分秒等(个人感觉像是平时用的model模型)
// 调用NSCalendar的components:fromDate:方法返回一个NSDateComponents对象
// 需要的参数分别components:所需要的日期单位 date:目标月份的date对象
// NSUInteger units = NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;//所需要日期单位
NSDateComponents *components = [calendar components:NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond fromDate:[NSDate date]];
//时钟偏转角度
CGFloat hoursAngle = (components.hour / 12.0) * M_PI * 2.0;
//分钟偏转角度
CGFloat minsAngle = (components.minute / 60.0) * M_PI * 2.0;
//秒钟旋转角度
CGFloat secsAngle = (components.second / 60.0) * M_PI * 2.0;
self.hourHand.transform = CGAffineTransformMakeRotation(hoursAngle);
self.minuteHand.transform = CGAffineTransformMakeRotation(minsAngle);
self.secondHand.transform = CGAffineTransformMakeRotation(secsAngle);
}
2.NSTimer定时器，重复秒针旋转动画
self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(tick) userInfo:nil repeats:YES];
3.设置时分秒图片layer的position位置(anchorPoint锚点位置)
self.secondHand.layer.anchorPoint = CGPointMake(0.5f, 0.9f);
self.minuteHand.layer.anchorPoint = CGPointMake(0.5f, 0.9f);
self.hourHand.layer.anchorPoint = CGPointMake(0.5f, 0.9f);
补充：锚点解释如下图：
锚点.png
下面是所有代码，控件是通过storyboard控件拉的。
storyboard控件.png
#import "ViewController.h"
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIImageView *hourHand;
@property (weak, nonatomic) IBOutlet UIImageView *minuteHand;
@property (weak, nonatomic) IBOutlet UIImageView *secondHand;
@property (weak, nonatomic) NSTimer *timer;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.secondHand.layer.anchorPoint = CGPointMake(0.5f, 0.9f);
self.minuteHand.layer.anchorPoint = CGPointMake(0.5f, 0.9f);
self.hourHand.layer.anchorPoint = CGPointMake(0.5f, 0.9f);
self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(tick) userInfo:nil repeats:YES];
[self tick];
}
- (void)tick{
// NSCalendarIdentifierGregorian : 指定日历的算法
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
// NSDateComponents封装了日期的组件,年月日时分秒等(个人感觉像是平时用的model模型)
// 调用NSCalendar的components:fromDate:方法返回一个NSDateComponents对象
// 需要的参数分别components:所需要的日期单位 date:目标月份的date对象
// NSUInteger units = NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;//所需要日期单位
NSDateComponents *components = [calendar components:NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond fromDate:[NSDate date]];
//时钟偏转角度
CGFloat hoursAngle = (components.hour / 12.0) * M_PI * 2.0;
//分钟偏转角度
CGFloat minsAngle = (components.minute / 60.0) * M_PI * 2.0;
//秒钟旋转角度
CGFloat secsAngle = (components.second / 60.0) * M_PI * 2.0;
self.hourHand.transform = CGAffineTransformMakeRotation(hoursAngle);
self.minuteHand.transform = CGAffineTransformMakeRotation(minsAngle);
self.secondHand.transform = CGAffineTransformMakeRotation(secsAngle);
}
