自定义 UITabBar 背景图像在 iOS 5 及更高版本中不起作用 [英] Custom UITabBar background image not working in iOS 5 and later

问题描述

我有一段简单的代码，用于在 tabBar 上放置背景图像.

I have a simple piece of code that places a background image on the tabBar.

UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"tabBG.png"]];
[self.tabBarController.tabBar insertSubview:imageView atIndex:0];
[imageView release];

这在 iOS 4 中运行良好，但在 iOS 5 中测试时，它不起作用.

This works fine in iOS 4 but when testing in iOS 5, it doesn't work.

我正在尝试执行以下操作:

I'm trying to do the following:

UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"tabBG.png"]];

NSString *reqSysVer = @"4.3";
NSString *iOSVersion = [[UIDevice currentDevice] systemVersion];

if ([iOSVersion compare:reqSysVer options:NSNumericSearch] !=NSOrderedDescending) {
    // code for iOS 4.3 or below
    [self.tabBarController.tabBar insertSubView:imageView atIndex:0];
}
else {
    // code for iOS 5
    [self.tabBarController.tabBar insertSubView:imageView atIndex:1];
}

[imageView release];

唉，这行不通……谁能提供解决方案?

Alas, this isn't working... Can anyone offer a solution?

推荐答案

iOS5 提供了 UIAppearance 代理.

iOS5 offers the UIAppearance Proxy.

此外，最佳实践是根据功能(在本例中是 RespondsToSelector)而不是 iOS 版本来切换您的代码 - 这是一个脆弱的假设(谁说它在未来不会改变).

Also, it's best practice to switch your code based on the capability (in this case it's respondsToSelector) instead of iOS version - that's a fragile assumption (who's to say it doesn't change in the future).

您可以仅为该实例或为所有标签栏全局设置它:

You can set it for just that instance or globally for all tab bars:

// not supported on iOS4    
UITabBar *tabBar = [tabController tabBar];
if ([tabBar respondsToSelector:@selector(setBackgroundImage:)])
{
    // set it just for this instance
    [tabBar setBackgroundImage:[UIImage imageNamed:@"tabbar_brn.jpg"]];

    // set for all
    // [[UITabBar appearance] setBackgroundImage: ...
}
else
{
    // ios 4 code here
}

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