ios wkWebViewローカルhtml(cssやjsなどのフォルダがある)

WKWebViewConfiguration *configuration = [[WKWebViewConfiguration alloc] init];
            [configuration setValue:@YES forKey:@"_allowUniversalAccessFromFileURLs"];
    //   
    CGFloat width = self.view.frame.size.width;
    CGFloat height = self.view.frame.size.height -20;
    webView = [[WKWebView alloc] initWithFrame:CGRectMake(0, 20, width, height) configuration:configuration];
    
    
    [self setAutomaticallyAdjustsScrollViewInsets:NO];
    webView.navigationDelegate = self;

    [self.view addSubview: webView];
    NSString *filePath = [[NSBundle mainBundle]pathForResource:@"index" ofType:@"html"];
//    NSString *htmlString = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:nil];
    NSURL *url = [NSURL fileURLWithPath:filePath];
    [webView loadRequest:[NSURLRequest requestWithURL:url]];