改变动画速率

speed 默认为1，如果动画时间为3秒，而想要将动画时间改为1.5秒，则speed 为之前的2倍

- (void)runOrStopRotateAnimation:(BOOL)run {
    
    if (!self.anchorConfiged) {
        self.anchorConfiged = YES;
        //先设置动画锚点
        self.indicatorView.layer.anchorPoint = CGPointMake(0.5, 1);
        
        //设置动画锚点后，视图坐标会发生变化，为了与锚点设置前显示一致，可以往反方向平移对应的距离
        CGAffineTransform transform = CGAffineTransformIdentity;
        transform = CGAffineTransformTranslate(transform, 0, self.indicatorView.frame.size.height*0.5);
        self.indicatorView.transform = transform;
    }
    
    //若未执行动画，且节拍器开始播放，则开启动画
    if (run && !self.animationRunning) {
        [self.indicatorView.layer removeAllAnimations];
        self.animationRunning = YES;
        CABasicAnimation *rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
        // 旋转角度
        rotationAnimation.fromValue = [NSNumber numberWithFloat:M_PI*-0.15];
        rotationAnimation.toValue = [NSNumber numberWithFloat:M_PI*0.15];
        rotationAnimation.duration = MetronomeDurationPerBPM;
        rotationAnimation.repeatCount = HUGE_VALF;
        // 动画结束时是否执行逆动画
        rotationAnimation.autoreverses = YES;
        rotationAnimation.fillMode = kCAFillModeForwards;
        rotationAnimation.removedOnCompletion = NO;
        [self.indicatorView.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"];
    }
    //若动画在执行，且节拍器停止，则关闭动画
    else if (!run && self.animationRunning) {
        self.animationRunning = NO;
        [self.indicatorView.layer removeAllAnimations];
    }
}

- (void)changeSilderAnimationSpeed:(float)speed {
    
    safe_dispatch_main_async(^{
        self.indicatorView.layer.timeOffset = [self.indicatorView.layer convertTime:CACurrentMediaTime() fromLayer:nil];
        self.indicatorView.layer.beginTime = CACurrentMediaTime();
        self.indicatorView.layer.speed = speed;
    });
}