- (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler
{
    
    //    1.拦截请求
    NSString *urlString = [navigationAction.request.URL absoluteString];
    
    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
    
}