WKUIDelegate中的代理方法主要涉及到界面显示的回调方法，原生控件支持，三种提示框：输入、确认、警告。首先将web提示框拦截然后再做处理。

方法介绍

• 创建新的webView时调用的方法

- (nullable WKWebView *)webView:(WKWebView *)webView createWebViewWithConfiguration:(WKWebViewConfiguration *)configuration forNavigationAction:(WKNavigationAction *)navigationAction windowFeatures:(WKWindowFeatures *)windowFeatures;

• 关闭webView时调用的方法

- (void)webViewDidClose:(WKWebView *)webView API_AVAILABLE(macosx(10.11), ios(9.0));

• 警告框

- (void)webView:(WKWebView *)webView runJavaScriptAlertPanelWithMessage:(NSString *)message initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(void))completionHandler;

• 确认框

- (void)webView:(WKWebView *)webView runJavaScriptConfirmPanelWithMessage:(NSString *)message initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(BOOL result))completionHandler;

• 输入框

- (void)webView:(WKWebView *)webView runJavaScriptTextInputPanelWithPrompt:(NSString *)prompt defaultText:(nullable NSString *)defaultText initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(NSString * _Nullable result))completionHandler;

• 能否预览用户触摸的元素

- (BOOL)webView:(WKWebView *)webView shouldPreviewElement:(WKPreviewElementInfo *)elementInfo API_AVAILABLE(ios(10.0));

• 定制预览控制器

- (nullable UIViewController *)webView:(WKWebView *)webView previewingViewControllerForElement:(WKPreviewElementInfo *)elementInfo defaultActions:(NSArray<id <WKPreviewActionItem>> *)previewActions API_AVAILABLE(ios(10.0));

• 可弹出的视图控制器

- (void)webView:(WKWebView *)webView commitPreviewingViewController:(UIViewController *)previewingViewController API_AVAILABLE(ios(10.0));

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