如果想着做一个类似的家里的圆形时钟的样式的钟表，可以使用这样的方法：
#import "ViewController.h"
@interface ViewController ()
@property (nonatomic ,weak)CALayer *second;
@property (nonatomic ,weak)CALayer *minute;
@property (nonatomic ,weak)CALayer *hour;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.view.backgroundColor = [UIColor cyanColor];
//创建表盘
CALayer *clock = [[CALayer alloc]init];
//大小
clock.bounds = CGRectMake(0, 0, 200, 200);
//位置
clock.position = CGPointMake(200, 200);
//内容
clock.contents = (__bridge id _Nullable)([UIImage imageNamed:@"clock"].CGImage);
[self.view.layer addSublayer:clock];
//圆角
clock.cornerRadius = 100;
//裁剪
clock.masksToBounds = YES;
//创建秒针
CALayer *second = [[CALayer alloc]init];
self.second = second;
//大小
second.bounds = CGRectMake(0, 0, 2, 100);
//位置
second.position = clock.position;
//颜色
second.backgroundColor = [UIColor redColor].CGColor;
//锚点
second.anchorPoint = CGPointMake(0.5, 0.8);
[self.view.layer addSublayer:second];
//创建分针
CALayer *minute = [[CALayer alloc]init];
self.minute = minute;
//大小
minute.bounds = CGRectMake(0, 0, 3, 80);
//位置
minute.position = clock.position;
//颜色
minute.backgroundColor = [UIColor blueColor].CGColor;
//锚点
minute.anchorPoint = CGPointMake(0.5, 0.8);
[self.view.layer addSublayer:minute];
//创建时针
CALayer *hour = [[CALayer alloc]init];
self.hour = hour;
//大小
hour.bounds = CGRectMake(0, 0, 4, 60);
//位置
hour.position = clock.position;
//颜色
hour.backgroundColor = [UIColor purpleColor].CGColor;
//锚点
hour.anchorPoint = CGPointMake(0.5, 0.8);
[self.view.layer addSublayer:hour];
CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(timeChange)];
[link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
[self timeChange];
}
-(void)timeChange{
NSDate *date = [NSDate date];
//
// NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
// formatter.dateFormat = @"ss";
// NSString *ms = [formatter stringFromDate:date];
// CGFloat msValue = [ms floatValue];
NSCalendar *cal = [NSCalendar currentCalendar];
CGFloat ms = [cal component:NSCalendarUnitNanosecond fromDate:date];
CGFloat s= [cal component:NSCalendarUnitSecond fromDate:date];
CGFloat m = [cal component:NSCalendarUnitMinute fromDate:date];
CGFloat h = [cal component:NSCalendarUnitHour fromDate:date];
//秒针角度
CGFloat angle = (2 * M_PI/60) / 1000000000;
CGFloat angle1 = 2 * M_PI / 60;
self.second.affineTransform = CGAffineTransformMakeRotation(angle1 * s + angle * ms);
//分针角度
CGFloat minuteAngle = 2 * M_PI / 60;
self.minute.affineTransform = CGAffineTransformMakeRotation(minuteAngle * m + angle1 * s / 60 + angle * ms / 60);
//时针角度
CGFloat hourAngle = 2 * M_PI / 12;
self.hour.affineTransform = CGAffineTransformMakeRotation(hourAngle * h + minuteAngle * m / 12 + angle1 * s / 60 + angle * ms / 60);
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end
当然还要有一个这样的表盘，
其实代码实现主要是用的CALayer的一些动画效果实现的。