UIImageView部分代码
_blurImageView = [[UIImageView alloc] init];
_blurImageView.clipsToBounds = YES;
_blurImageView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
_blurImageView.contentMode = UIViewContentModeScaleAspectFill;
[self addSubview:_blurImageView];
UIVisualEffectView部分代码
UIBlurEffect *beffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleLight];
_imageEffectView = [[UIVisualEffectView alloc]initWithEffect:beffect];
_imageEffectView.alpha = 0;
_imageEffectView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
[self addSubview:_imageEffectView];
二：滚动视图
滚动视图需要做的就是设置 contentInset ，让出一部分空间给头部视图。这里如果将头部视图直接加到滚动视图上，无法做到头部视图最后悬停在一定位置，因此直接加到和滚动视图同级就行。
示例代码
self.webView = [[WKWebView alloc] initWithFrame:CGRectMake(0, 0, kWindowWidth, kWindowHeight)];
self.webView.backgroundColor = [UIColor clearColor];
[self.view addSubview:self.webView];
NSURL * url = [NSURL URLWithString:@"https://www.easck.com/"];
NSMutableURLRequest *re = [NSMutableURLRequest requestWithURL:url];
[self.webView loadRequest:re];
//初始化header
self.headerView.headerImage = [UIImage imageNamed:@"saber.jpeg"];
self.headerView.tittle = @"哈哈是个demo";
self.headerView.isShowLeftButton = YES;
self.headerView.isShowRightButton = YES;
__weak typeof(self) weakSelf = self;
self.headerView.leftClickBlock = ^(UIButton *btn){
[weakSelf.navigationController popViewControllerAnimated:YES];
};
self.headerView.rightClickBlock = ^(UIButton *btn){
NSLog(@"点击了分享");
};
[self.webView.scrollView handleSpringHeadView:self.headerView];
三：控制头部动画
和其他的滚动视图做动画一样，实现滚动视图的代理方法scrollViewDidScroll，获取偏移量，然后根据一定的规则做动画，这里为了解耦，也为了复用，使用了在scrollView的分类中监听scrollView的contentOffset方法去实现动画控制。
