关于initWithNavigationBarClass的困惑 - 如何使用(new instanceType方法) [英] Confusion about initWithNavigationBarClass - how to use (new instanceType method)
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问题描述
这很好用:
UINavigationController *nc =
[[UINavigationController alloc]
initWithNavigationBarClass:[GTScrollNavigationBar class]
toolbarClass:[UIToolbar class]];
nc.viewControllers = @[firstPage];
self.window.rootViewController = nc;
但 不 工作:
but this does not work:
UINavigationController *nc =
[[UINavigationController alloc]
initWithNavigationBarClass:[GTScrollNavigationBar class]
toolbarClass:[UIToolbar class]];
self.window.rootViewController = nc;
self.window.rootViewController.viewControllers = @[firstPage]; // ERROR
怎么会这样?谢谢
推荐答案
self.window.rootViewController.viewControllers = @[firstPage];
无法编译,因为 rootViewController
属性 UIWindow
被声明为
作为(通用) UIViewController
(没有 viewControllers
property),而不是 UINavigationController
。
does not compile because the rootViewController
property of UIWindow
is declared
as a (generic) UIViewController
(which does not have a viewControllers
property), and not as a UINavigationController
.
编译器没有知道你的情况下,根视图控制器实际上是一个导航
控制器。
The compiler does not "know" that the root view controller is actually a navigation controller in your case.
所以要么你在第一个代码块中继续,要么你有添加显式强制转换:
So either you proceed as in your first code block, or you have to add an explicit cast:
((UINavigationController *)self.window.rootViewController).viewControllers = @[firstPage];
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