导航栏颜色渐变

1、导航栏开始时是没有导航栏的感觉，往上滚动后又出现导航栏，采用下面的方法

- (void)scrollViewDidScroll:(UIScrollView *)scrollView

{

CGFloat minAlphaOffset = - 88;

CGFloat maxAlphaOffset = 200;

CGFloat offset = scrollView.contentOffset.y;

CGFloat alpha;

if (offset <= 0) {

alpha = 0.0;

} else {

alpha = (offset - minAlphaOffset) / (maxAlphaOffset - minAlphaOffset);

}

UIView *barImageView = self.navigationController.navigationBar.subviews.firstObject;

barImageView.alpha = alpha;

}

//设置透明导航栏

UIView *barImageView = self.navigationController.navigationBar.subviews.firstObject;

barImageView.alpha = 0.0;

原文地址：https://www.cnblogs.com/xiaonizicome/p/10436359.html