iOS 在使用WKWebView的时候一般会在请求里面添加请求头，但是当进入到二级页面的时候就会发现请求头丢掉了，本人找了一个比较笨笨的办法维持住请求头

• 注意 appNavigationUrl 是请求头的key

初始化wkwebView的时候设置上header 
 WKWebViewConfiguration * config = [[WKWebViewConfiguration alloc] init];
    WKCookiesManager * cookieManager = [WKCookiesManager shareCookies];
    config.processPool = cookieManager.processPool;
    WKPreferences * prefer = [[WKPreferences alloc] init];
    prefer.javaScriptEnabled = YES;
    prefer.javaScriptCanOpenWindowsAutomatically = YES;
    config.preferences = prefer;
    self.webView = [[WKWebView alloc] initWithFrame:CGRectMake(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT) configuration:config];
    self.webView.allowsBackForwardNavigationGestures = YES;
    [self.view addSubview:self.webView];
    self.webView.UIDelegate = self;
    self.webView.navigationDelegate = self;
    NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:self.url] cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:timeOutTime];
    [request addValue:_fatherUrl forHTTPHeaderField:@"appNavigationUrl"];
    [self.webView loadRequest:request];

-(void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler
开始加载的时候判断是否有header 
NSURLRequest * request =   navigationAction.request;
  NSMutableURLRequest * mutRequest = [request mutableCopy];
  NSString * urlString = request.URL.absoluteString;
  NSLog(@"====== >>>>url----- %@ request %@",urlString,[request allHTTPHeaderFields]);
  NSDictionary * dictHader = request.allHTTPHeaderFields;
  if (![dictHader objectForKey:@"appNavigation"]) {
      [mutRequest addValue:@"true" forHTTPHeaderField:@"appNavigation"];
      [webView loadRequest:mutRequest];
      decisionHandler(WKNavigationActionPolicyCancel);
  }