文章：https://kunnan.blog.csdn.net/article/details/73971895 1、解决的问题：Avoiding iOS bug:UIWebView with file input doesn‘t work in modal view controller 2、解决思路:使dismissViewControllerAnimated调用一次，或者让UIDocumentMenuViewController找不到presentingViewController 3、应用场景:modal UIWebView and camera/image picker