speed 默認為1，如果動畫時間為3秒，而想要將動畫時間改為1.5秒，則speed 為之前的2倍

- (void)runOrStopRotateAnimation:(BOOL)run {
    
    if (!self.anchorConfiged) {
        self.anchorConfiged = YES;
        //先設置動畫錨點
        self.indicatorView.layer.anchorPoint = CGPointMake(0.5, 1);
        
        //設置動畫錨點后，視圖坐標會發(fā)生變化，為了與錨點設置前顯示一致，可以往反方向平移對應的距離
        CGAffineTransform transform = CGAffineTransformIdentity;
        transform = CGAffineTransformTranslate(transform, 0, self.indicatorView.frame.size.height*0.5);
        self.indicatorView.transform = transform;
    }
    
    //若未執(zhí)行動畫，且節(jié)拍器開始播放，則開啟動畫
    if (run && !self.animationRunning) {
        [self.indicatorView.layer removeAllAnimations];
        self.animationRunning = YES;
        CABasicAnimation *rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
        // 旋轉角度
        rotationAnimation.fromValue = [NSNumber numberWithFloat:M_PI*-0.15];
        rotationAnimation.toValue = [NSNumber numberWithFloat:M_PI*0.15];
        rotationAnimation.duration = MetronomeDurationPerBPM;
        rotationAnimation.repeatCount = HUGE_VALF;
        // 動畫結束時是否執(zhí)行逆動畫
        rotationAnimation.autoreverses = YES;
        rotationAnimation.fillMode = kCAFillModeForwards;
        rotationAnimation.removedOnCompletion = NO;
        [self.indicatorView.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"];
    }
    //若動畫在執(zhí)行，且節(jié)拍器停止，則關閉動畫
    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;
    });
}