- (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler {
    //    1.拦截请求
        NSString *urlString = [navigationAction.request.URL absoluteString];
        //    2.跳转别的应用如系统浏览器（跨域跳转）、应用的web内跳转（不跨域跳转）
        NSString *hostname = navigationAction.request.URL.host.lowercaseString;
        if (navigationAction.navigationType == WKNavigationTypeLinkActivated) {//跳转别的应用如系统浏览器
            // 对于跨域，需要手动跳转
            [[UIApplication sharedApplication] openURL:navigationAction.request.URL];
            // 不允许web内跳转
            decisionHandler(WKNavigationActionPolicyCancel);
        } else {//应用的web内跳转
            decisionHandler (WKNavigationActionPolicyAllow);
        }
        return ;//不添加会崩溃
}