如何在每页的基础上更改NavigationBar的背景图像？ [英] How can I change the background image for my NavigationBar on a per page basis?

问题描述

我一直在寻找一种方法来改变我的 NavigationBar 的背景图像，并控制我的 NavigationBar 当用户导航应用时。

I've been looking around for a way to change the background image of my NavigationBar and control the appearance of my NavigationBar as the user navigates the app.

我知道更改背景图片的可接受方法是：

I understand that the accepted approach for changing the background image is :

@implementation UINavigationBar (UINavigationBarCategory)

- (void)drawRect:(CGRect)rect {
     UIImage *image = [UIImage imageNamed: @"navbar.png"];
     [image drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
}

@end

然而，这改变了外观整个应用程序中的 NavigationBar 当用户从一个视图导航到下一个视图时，如何更改 NavBar 的背景图像？

However, that changes the appearance of the NavigationBar throughout the whole app. How can I change the background image of the NavBar as the user navigates from one view to the next?

谢谢提前帮助你！

推荐答案

您需要在当前页面或当前适当的图像上设置一些状态，可能是在每个 viewWillAppear：方法中。然后修改上面的 drawRect：函数以引用该状态。

You need to set some state somewhere about the current page or currently appropriate image to use, probably in each of your viewWillAppear: methods. Then modify your drawRect: function above to reference that state.

要使条形图重绘，请调用<更新状态时code> [myNavigationBar setNeedsDisplay] 。这将导致调用 drawRect 。

To cause the bar to be redrawn, call [myNavigationBar setNeedsDisplay] when you update the state. This will cause drawRect to be invoked.

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