使用场景：UIViewController1 打开 UIViewController2（背景半透明弹窗）

案例：打开富文本网页<img>图片的url查看图片详情

WKWebView  WKNavigationDelegate代理方法设置js代码点击事件 

///注册添加图片标签点击js方法
- (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation{///js添加图片点击事件NSString *jsClickImage =@"function registerImageClickAction(){var imgs=document.getElementsByTagName('img');var length=imgs.length;for(var i=0; i < length;i++){img=imgs[i];if(\"ad\" ==img.getAttribute(\"flag\")){var parent = this.parentNode;if(parent.nodeName.toLowerCase() != \"a\")return;}img.onclick=function(){window.location.href='image-preview:'+this.src}}}";[webView evaluateJavaScript:jsClickImage completionHandler:nil];[webView evaluateJavaScript:@"registerImageClickAction()" completionHandler:nil];[webView evaluateJavaScript:@"document.body.scrollHeight" completionHandler:^(id _Nullable result,NSError *_Nullable error) {//获取webView内容高度CGFloat height = [result doubleValue];
//        [webView mas_updateConstraints:^(MASConstraintMaker *make) {
//              make.height.equalTo(@(height));
//        }];webView.frame = CGRectMake(0, 0, self.frame.size.width, height);[webView layoutIfNeeded];[webView setNeedsLayout];if (self.contentHeightCallback != nil) {self.contentHeightCallback(CGSizeMake(self.frame.size.width, height));}}];}///拦截点击图片
- (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler{NSString *requestString = navigationAction.request.URL.absoluteString;NSString *imgKey = @"image-preview";if([requestString hasPrefix: imgKey]){NSString *url = [requestString substringFromIndex:imgKey.length+1];//查看图片详情[self showPicDetail:url];decisionHandler(WKNavigationActionPolicyCancel);return;}decisionHandler(WKNavigationActionPolicyAllow);
}

showPicDetail:()  方法打开浮窗：

-(void) showPicDetail:(NSString *)imgUrl{ShowBigPicDetailViewController *vc = [[ShowBigPicDetailViewController alloc] init];vc.imageUrl = imageUrl;//设置全屏显示   关键语句，必须有vc.modalPresentationStyle = UIModalPresentationOverCurrentContext;[self presentViewController:vc animated:YES completion:nil];
}

设置UIViewController2 背景半透明

- (void)viewDidLoad {[super viewDidLoad];//设置半透明背景[self.view setBackgroundColor:[UIColor colorWithRed:0 green:0 blue:0 alpha:0.5f]];...
}

关闭浮窗弹窗：

[self dismissViewControllerAnimated:YES completion:nil];