效果图

实现思路

• 该示例通过隐式动画实现
  
• 表盘通过显示在imageView中的一张图片来实现
  

• 在表盘上绘制（时分秒）三条直线，分别位于不同的图层，且时针位于最下层，秒针位于最上层

  • 设置直线为圆角
    
  • 直线的一段位于表盘的圆心
    
  • 通过NSTimer定时器，使不同的图层定时执行对应的动画

实现步骤

• 通过storyboard创建表盘，并拥有它

  @PRoperty (weak, nonatomic) IBOutlet UIImageView *clockView;

• 使用三个成员变量来保存时分秒三根表针位于的不同图层

  @property (nonatomic, weak) CALayer *secondLayer;
  @property (nonatomic, weak) CALayer *minuteLayer;
  @property (nonatomic, weak) CALayer *hourLayer;

• 初始化所用到的常量

  //将旋转角度转换为弧度制
  #define angleToRadion(angle) ((angle) / 180.0 * M_PI)
  
  //秒针每秒钟转过的角度
  #define perSecondAngle 6
  //分针每分钟转过的角度
  #define perMinuteAngle 6
  //时针每小时转过的角度
  #define perHourAngle 30
  //时针每分钟转过的角度
  #define perMuniteHourAngle 0.5

• 设置时分秒三根表针

  • 设置时针

    - (void)setUpHourLayer
    {
    	//创建图层
    	CALayer *layer = [CALayer layer];
    	layer.backgroundColor = [UIColor blackColor].CGColor;
    	layer.cornerRadius = 8;
    
    	设置图层的锚点
    	layer.anchorPoint = CGPointMake(0.5, 1);
    	//设置图层的位置和尺寸
    	layer.position = CGPointMake(kClockWith * 0.5, kClockWith * 0.5);
    	layer.bounds = CGRectMake(0, 0, 5, kClockWith * 0.5 - 44);
    
    	//将图层添加到父图层中
    	[self.clockView.layer addSublayer:layer];
    	self.hourLayer = layer;
    }

  • 设置分针

    - (void)setUpMinuteLayer
    {
        CALayer *layer = [CALayer layer];
        layer.backgroundColor = [UIColor blackColor].CGColor;
        layer.cornerRadius = 4;
    
        //设置锚点
        layer.anchorPoint = CGPointMake(0.5, 1);
    
        //设置位置和尺寸
        layer.position = CGPointMake(kClockWith * 0.5, kClockWith * 0.5);
        layer.bounds = CGRectMake(0, 0, 3, kClockWith * 0.5 - 34);
    
        //将图层添加到父图层中
        [self.clockView.layer addSublayer:layer];
        self.minuteLayer = layer;
    }

  • 设置秒针

    - (void)setUpSecondLayer
    {
        CALayer *layer = [CALayer layer];
        layer.backgroundColor = [UIColor redColor].CGColor;
    
        //设置锚点
        layer.anchorPoint = CGPointMake(0.5, 1);
    
        //设置位置和尺寸
        layer.position = CGPointMake(kClockWith * 0.5, kClockWith * 0.5);
        layer.bounds = CGRectMake(0, 0, 1, kClockWith * 0.5 - 24);
    
        //将图层添加到父图层中
        [self.clockView.layer addSublayer:layer];
        self.secondLayer = layer;
    }

• 设置定时器，定时执行动画

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

• 设置定时器触发时调用的方式，添加动画代码

  - (void)timeChange
  {
      //获取日历对象
      NSCalendar *calendar = [NSCalendar currentCalendar];
  
      //获取日期组件
      NSDateComponents *components = [calendar components:NSCalendarUnitSecond | NSCalendarUnitMinute | NSCalendarUnitHour fromDate:[NSDate date]];
  
      //获取当前的时分秒值
      NSInteger second = components.second;
      NSInteger munite = components.minute;
      NSInteger hour = components.hour;
  
      //计算当前时分秒表针转过的角度（弧度制）
      CGFloat secondAngle = angleToRadion(second * perSecondAngle);
      CGFloat muniteAngle = angleToRadion(munite * perMinuteAngle);
      CGFloat hourAngle = angleToRadion(hour *perHourAngle + munite * perMuniteHourAngle);
  
      //修改时分秒表针位于的图层的transform属性，执行隐式动画
      self.secondLayer.transform = CATransform3DMakeRotation(secondAngle, 0, 0, 1);
      self.minuteLayer.transform = CATransform3DMakeRotation(muniteAngle, 0, 0, 1);
      self.hourLayer.transform = CATransform3DMakeRotation(hourAngle, 0, 0, 1);
  }