CALayer的基本使用

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CALayer的基本属性在这里不多说了，网上对属性和方法介绍的很清楚，下面直接上demo效果

时钟

这里写图片描述

主要使用到的几个知识点

anchorPoint（锚点）与position的使用
用NSCalendar和NSDateComponents拿到日期的组件

#import "ViewController.h"// 每秒秒针转6°#define kPerSecondA 6// 每分钟分针转6°#define kPerMinuteA 6// 每小时时针转30°#define kPerHourA 30// 每分钟时针转0.5°#define kPerMinHourA 0.5@interface ViewController ()@property (weak, nonatomic) IBOutlet UIImageView *imageView;@property (weak, nonatomic)  CALayer *secLayer;@property (weak, nonatomic)  CALayer *minLayer;@property (weak, nonatomic)  CALayer *hourLayer;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    // Do any additional setup after loading the view, typically from a nib.    // 小时    [self setUpHourLayer];    // 分    [self setUpMinLayer];    // 秒    [self setUpSecLayer];    // 定时器    [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timeChange) userInfo:nil repeats:YES];    // 初始化始终    [self timeChange];}- (void)timeChange{    // 获取当前是多少秒    // 获取当前的日历对象    NSCalendar *calendar = [NSCalendar currentCalendar];    // 日期组件:秒,分,小时,年,月,日......    // NSCalendarUnit:表示日期组件有哪些组成    NSDateComponents *dataCmp = [calendar components:NSCalendarUnitSecond | NSCalendarUnitMinute | NSCalendarUnitHour fromDate:[NSDate date]];    // 获取分    NSInteger minute = dataCmp.minute;    // 计算下分针转多少度    CGFloat minA = (minute * kPerMinuteA) / 180.0 * M_PI;    // 旋转分针    _minLayer.transform = CATransform3DMakeRotation(minA, 0, 0, 1);    // 获取小时    NSInteger hour = dataCmp.hour;    // 计算时针转多少度 = 当前有多少小时 * 每小时转的度数30° + 当前多少分钟 * 每分钟时针转多少0.5    CGFloat hourA = (hour * kPerHourA + minute * kPerMinHourA) / 180.0 * M_PI;    // 旋转时针    _hourLayer.transform = CATransform3DMakeRotation(hourA, 0, 0, 1);    // 获取秒数    NSInteger sec = dataCmp.second;    // 秒针转多少度    CGFloat secA = (sec * kPerSecondA) / 180.0 * M_PI;    // 旋转秒针    _secLayer.transform = CATransform3DMakeRotation(secA, 0, 0, 1);}// 秒- (void)setUpSecLayer{    CALayer *layer = [CALayer layer];    _secLayer = layer;    layer.backgroundColor = [UIColor redColor].CGColor;    // 绕着锚点旋转,设置锚点    layer.anchorPoint = CGPointMake(0.5, 1);    layer.position = CGPointMake(_imageView.bounds.size.width * 0.5, _imageView.bounds.size.height * 0.5);    layer.bounds = CGRectMake(0, 0, 1, 80);    [_imageView.layer addSublayer:layer];}// 分- (void)setUpMinLayer{    CALayer *layer = [CALayer layer];    _minLayer = layer;    layer.cornerRadius = 4;    layer.backgroundColor = [UIColor blackColor].CGColor;    // 绕着锚点旋转,设置锚点    layer.anchorPoint = CGPointMake(0.5, 1);    layer.position = CGPointMake(_imageView.bounds.size.width * 0.5, _imageView.bounds.size.height * 0.5);    layer.bounds = CGRectMake(0, 0, 4, 80);    [_imageView.layer addSublayer:layer];}// 小时- (void)setUpHourLayer{    CALayer *layer = [CALayer layer];    _hourLayer = layer;    layer.cornerRadius = 4;    layer.backgroundColor = [UIColor blackColor].CGColor;    // 绕着锚点旋转,设置锚点    layer.anchorPoint = CGPointMake(0.5, 1);    layer.position = CGPointMake(_imageView.bounds.size.width * 0.5, _imageView.bounds.size.height * 0.5);    layer.bounds = CGRectMake(0, 0, 4, 75);    [_imageView.layer addSublayer:layer];}

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