CABasicAnimation 实现颜色渐变动画

利用 CABasicAnimation 实现颜色的渐变动画

- (void)doAnimation:(BOOL)hidden{
    CABasicAnimation *anim1 = [CABasicAnimation animationWithKeyPath:@"backgroundColor"];
    anim1.duration = 0.2;
    anim1.fromValue = hidden ? (__bridge id _Nullable)([UIColor whiteColor].CGColor) : (__bridge id _Nullable)([UIColor blackColor].CGColor);
    anim1.toValue = hidden ? (__bridge id _Nullable)([UIColor blackColor].CGColor) : (__bridge id _Nullable)([UIColor whiteColor].CGColor);
    //填充效果：动画结束后，动画将保持最后的表现状态
    anim1.fillMode = kCAFillModeForwards;
    anim1.removedOnCompletion = NO;
    anim1.beginTime = 0.0f;
    [self.mainScrollView.layer addAnimation:anim1 forKey:@"backgroundColor"];
    
}- (void)