iOS navigationBar和tabBar变透明 & navigationBar根据滑动距离的渐变色实现

[b]navigationBar变为纯透明[/b]

//第一种方法

//导航栏纯透明

[self.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];

//去掉导航栏底部的黑线

self.navigationBar.shadowImage = [UIImage new];

//第二种方法

[[self.navigationBar subviews] objectAtIndex:0].alpha = 0;

[b]tabBar同理[/b]

[self.tabBar setBackgroundImage:[UIImage new]];

self.tabBar.shadowImage = [UIImage new];

[b]navigationBar根据滑动距离的渐变色实现[/b]

//第一种

- (void)scrollViewDidScroll:(UIScrollView *)scrollView

{

CGFloat offsetToShow = 200.0;//滑动多少就完全显示

CGFloat alpha = 1 - (offsetToShow - scrollView.contentOffset.y) / offsetToShow;

[[self.navigationController.navigationBar subviews] objectAtIndex:0].alpha = alpha;

}

//第二种

- (void)scrollViewDidScroll:(UIScrollView *)scrollView

{

CGFloat offsetToShow = 200.0;

CGFloat alpha = 1 - (offsetToShow - scrollView.contentOffset.y) / offsetToShow;

[self.navigationController.navigationBar setShadowImage:[UIImage new]];

[self.navigationController.navigationBar setBackgroundImage:[self imageWithColor:[[UIColor orangeColor]colorWithAlphaComponent:alpha]] forBarMetrics:UIBarMetricsDefault];

}

//生成一张纯色的图片

- (UIImage *)imageWithColor:(UIColor *)color

{

CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);

UIGraphicsBeginImageContext(rect.size);

CGContextRef context = UIGraphicsGetCurrentContext();

CGContextSetFillColorWithColor(context, [color CGColor]);

CGContextFillRect(context, rect);

UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

return theImage;

}