核心动画——基础动画

//开始选号
- (IBAction)startChoose {
    //停掉定时器
    [self stopRotating];
    
    //核心动画-基础动画
    CABasicAnimation *anim = [CABasicAnimation animation];
    anim.keyPath = @"transform.rotation";
    anim.toValue = @(2 * M_PI * 3);
    anim.duration = 1.5;
//    anim.repeatCount = 3;
    
    //开始和结尾比较慢，中间快
    anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    anim.delegate = self;
    [self.centerWheel.layer addAnimation:anim forKey:nil];
    
    //不能被点击
    self.userInteractionEnabled = NO;
}

//动画停止之后执行
- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag
{
    self.userInteractionEnabled = YES;
    
    //2秒后执行
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        //调用开始转动的方法
        [self statrRotating];
    });
    
}