CADisplayLink做定时器任务

/**
 *  开始旋转
 */
- (void)statrRotating
{
    //1秒内刷新60次
    CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(update)];
    
    //添加到消息循环,link才能工作
    [link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
}

- (void)update
{
    //transform要一直转,就要一直累加角度
    self.centerWheel.transform = CGAffineTransformRotate(self.centerWheel.transform, M_PI / 200 );
}