导航栏渐变透明

刺骨的言语ヽ痛彻心扉 2023-10-17 08:48 74阅读 0赞

下载地址[Demo下载][Demo]

导航栏渐变透明

- (void)viewDidLoad {
        [super viewDidLoad];
        self.title = @"首页";
        
        [self setNavigation];
        
        [self setSubview];
    }
    
    - (void)setNavigation
    {
        [alphaView removeFromSuperview];
        CGRect frame = self.navigationController.navigationBar.frame;
        alphaView = [[UIView alloc] initWithFrame:CGRectMake(0, -20, frame.size.width, frame.size.height+20)];
        alphaView.backgroundColor = [UIColor purpleColor];
        alphaView.alpha = 0.0;
        alphaView.userInteractionEnabled = NO;
        [self.navigationController.navigationBar insertSubview: alphaView atIndex:0];
        barImageView = self.navigationController.navigationBar.subviews.firstObject;
        [self.navigationController.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsCompact];
        [self.navigationController.navigationBar setShadowImage:[UIImage new]];
    }
    
    - (void)setSubview
    {
        scroll_main = [[UIScrollView alloc]initWithFrame:CGRectMake(0, 64, [UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height)];
        scroll_main.delegate = self;
        scroll_main.backgroundColor = [UIColor cyanColor];
        scroll_main.showsVerticalScrollIndicator = NO;
        scroll_main.showsHorizontalScrollIndicator = NO;
        scroll_main.contentSize = CGSizeMake([UIScreen mainScreen].bounds.size.width, 2000);
        [self.view addSubview:scroll_main];
    }
    
    - (void)scrollViewDidScroll:(UIScrollView *)scrollView {
        CGFloat minAlphaOffset = - 64 - 10;
        CGFloat maxAlphaOffset = 200;
        CGFloat offset = scroll_main.contentOffset.y;
        CGFloat alpha;
        if (offset == 0) {
            alpha = 0;
        }
        else
        {
            alpha = (offset - minAlphaOffset) / (maxAlphaOffset - minAlphaOffset);
        }
        barImageView.alpha = alpha;
    }

![Center][]

[Demo]: http://download.csdn.net/detail/minggeqingchun/9633605
[Center]: https://img-blog.csdn.net/20160918095536889?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQv/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center