使用Xcode 4.2支持版本4.0到5.0的iPhone版本

Question

Hi i am working on iOS SDK5 with xcode 4.2 and i want to prepare a build which should be compatible with iOS 4.0 to 5.0 or at least 4.3 and 5.0

I have set the base sdk to 5.0 and deployment target to 4.0 but when i run the app in the iPhone 4 simulator my application crashes basically due to the code written below

[testNavigationBar setBackgroundImage:[UIImage imageNamed:@"facebook-navbar.png"] forBarMetrics:UIBarMetricsDefault];

but the above code runs fine when i switch the iPhone simulator from 4 to 5 also i have tried setBackgroundColor but its not working so kindly help me on this.

Answer 1

The problem is that method was added to iOS5, so it doesn't exist in iOS4. You need to do a runtime check to see if you're in iOS5, like the following:

if ([testNavigationBar respondsToSelector:@selector(setBackgroundImage:forBarMetrics)]) {
    [testNavigationBar setBackgroundImage:[UIImage imageNamed:@"facebook-navbar.png"] forBarMetrics:UIBarMetricsDefault];
}

Now the problem is that you won't get the background in iOS4, so you'll have to find a workaround.

Answer 2

That's because -setBackgroundImage: was introduced in iOS 5, and Apple don't (usually) back port new API to older platforms as a rule. Anyway, you have two options:

if ([testNavigationBar respondsToSelector:@selector(setBackgroundImage:)]) {
  // do what you're currently trying
}
else {
  //find a compatible way to do it
}

or:

//find a compatible way to do it

Answer 3

For iOS version 4.x, you can always override the UINavigationBar drawRect. Here is a posting on Stack Overflow on this very subject:

Background image for navigation view