‘’‘’
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)

    self.navigationController?.navigationBar.setBackgroundImage(UIImage(), forBarMetrics: .Default)
    self.navigationController?.navigationBar.shadowImage = UIImage()
    //如果导航栏有背景色，也需要修改下
    self.navigationController?.navigationBar.barTintColor = UIColor.clearColor()
    self.navigationController?.navigationBar.translucent = true

    for subview in self.view.subviews {
        if subview.isKindOfClass(UIWebView) {
            let webview = subview as! UIWebView
            //webview的y轴起点默认为64
            webview.scrollView.contentInset = UIEdgeInsets(top: -64, left: 0, bottom: 0, right: 0)
        }
    }
}

override func viewWillDisappear(animated: Bool) {
    super.viewWillDisappear(animated)

    self.navigationController?.navigationBar.setBackgroundImage(nil, forBarMetrics: .Default)
    self.navigationController?.navigationBar.shadowImage = nil
    self.navigationController?.navigationBar.translucent = false
}

‘’‘’