c# / Xamarin解决方案

NavigationController.NavigationBar.SetBackgroundImage(new UIImage(), UIBarMetrics.Default);
NavigationController.NavigationBar.ShadowImage = new UIImage();
NavigationController.NavigationBar.Translucent = true;

c# / Xamarin解决方案

NavigationController.NavigationBar.SetBackgroundImage(new UIImage(), UIBarMetrics.Default);
NavigationController.NavigationBar.ShadowImage = new UIImage();
NavigationController.NavigationBar.Translucent = true;

试试下面这段代码:

self.navigationController.navigationBar.translucent = YES;

如果有人想知道如何在iOS 7+中实现这一点，这里有一个解决方案(iOS 6也兼容)

在objective - c中

[self.navigationBar setBackgroundImage:[UIImage new]
                         forBarMetrics:UIBarMetricsDefault];
self.navigationBar.shadowImage = [UIImage new];
self.navigationBar.translucent = YES;

swift 3 (iOS 10)

self.navigationBar.setBackgroundImage(UIImage(), for: .default)
self.navigationBar.shadowImage = UIImage()
self.navigationBar.isTranslucent = true

在swift 2中

self.navigationBar.setBackgroundImage(UIImage(), forBarMetrics: .Default)
self.navigationBar.shadowImage = UIImage()
self.navigationBar.translucent = true

讨论

将导航栏上的半透明设置为YES就可以了，这是由于UINavigationBar文档中讨论的行为。我将在这里报告相关片段:

如果在具有不透明自定义背景图像的导航栏上将此属性设置为YES，则导航栏将对图像应用小于1.0的系统不透明度。

extension UINavigationBar {
var isTransperent: Bool {
        get {
            return false // Just to satisfy property
        }
        set {
            if newValue {
                self.shadowImage = UIImage()
                self.isTranslucent = true
                self.setBackgroundImage(UIImage(), for: .default)
            } else {
                self.shadowImage = UIImage()
                self.isTranslucent = false
                self.setBackgroundImage(nil, for: .default)
            }
        }
    }
}

这似乎很有效:

@implementation UINavigationBar (custom)
- (void)drawRect:(CGRect)rect {}
@end

navigationController.navigationBar.backgroundColor = [UIColor clearColor];