当用户在表格视图中向下滚动时，如何将UINavigationBar背景颜色从清除更改为红色

Question

我有一个桌面视图和一个导航栏。 我希望当用户向下滚动时，导航栏的背景颜色开始从清除变为红色，如增加alpha。

问题在于，当用户向下滚动导航栏背景alpha为1.0时，用户仍然可以在导航栏后面看到！

这是我的代码：

override func viewDidLoad() {
    super.viewDidLoad()

    self.mainProfileTableView.contentInset = UIEdgeInsetsMake(-44,0,0,0);


    self.navigationController?.navigationBar.isOpaque = true
    UIApplication.shared.statusBarView?.backgroundColor = UIColor.init(red: 180/255, green: 40/255, blue: 56/255, alpha: 1.0)

    self.navigationController?.navigationBar.barTintColor = UIColor.init(red: 180/255, green: 40/255, blue: 56/255, alpha: 1.0)


    self.navigationController?.navigationBar.setBackgroundImage(UIImage(named : "navigationBarBackGround"), for: .default)

    self.navigationController?.navigationBar.shadowImage = UIImage()
    self.navigationController?.navigationBar.isTranslucent = true
    self.navigationController?.view.backgroundColor = UIColor.init(red: 180/255, green: 40/255, blue: 56/255, alpha: 1.0)

}

这是检测用户向上或向下滚动的方法

var lastContentOffset: CGFloat = 0


func scrollViewDidScroll(_ scrollView: UIScrollView) {
    if (self.lastContentOffset < scrollView.contentOffset.y) {
        // moved to top
        print("move Up\(scrollView.contentOffset.y)")
        print("alpha\(Float(scrollView.contentOffset.y / 166))")
        navigationController?.navigationBar.alpha = scrollView.contentOffset.y / 166

    } else if (self.lastContentOffset > scrollView.contentOffset.y) {
        // moved to bottom

        navigationController?.navigationBar.alpha = scrollView.contentOffset.y / 166
        print("alpha\(Float(scrollView.contentOffset.y / 166))")
        print("move down\(scrollView.contentOffset.y)")

    } else {

        // didn't move
    }
}

Answer 1

可以是导航栏半透明吗？ 像这样：

使用以下方式更改：

self.navigationController?.navigationBar.isTranslucent = False

并删除：

self.navigationController?.navigationBar.setBackgroundImage...
self.navigationController?.navigationBar.shadowImage = UIImage()

然后在用户滚动时修改barTintColor。

Answer 2

感谢您的帮助但是我应该在滚动视图更改方法中使用半透明假，所以答案就是这个

func scrollViewDidScroll(_ scrollView: UIScrollView) {
if (self.lastContentOffset < scrollView.contentOffset.y) {
    // moved to top
    print("move Up\(scrollView.contentOffset.y)")
    print("alpha\(Float(scrollView.contentOffset.y / 166))")
    navigationController?.navigationBar.alpha = scrollView.contentOffset.y / 166
    if Float(scrollView.contentOffset.y / 166) >= 1.0 {

            self.navigationController?.navigationBar.isTranslucent = false

            }

} else if (self.lastContentOffset > scrollView.contentOffset.y) {
    // moved to bottom

    navigationController?.navigationBar.alpha = scrollView.contentOffset.y / 166
    print("alpha\(Float(scrollView.contentOffset.y / 166))")
    print("move down\(scrollView.contentOffset.y)")

} else {

    // didn't move
}
}