通过xib .........很容易迁移iPhone5和iPhone4

UIViewController *viewController3;
if ([[UIScreen mainScreen] bounds].size.height == 568)
{
    UIViewController *viewController3 = [[[mainscreenview alloc] initWithNibName:@"iphone5screen" bundle:nil] autorelease];               
}    
else
{
     UIViewController *viewController3 = [[[mainscreenview alloc] initWithNibName:@"iphone4screen" bundle:nil] autorelease];
}

使用视图的自动布局功能。它将自动调整到所有分辨率。

为控制器名称后缀为~iphone或~ipad的控制器创建两个xib。在编译时，Xcode将根据设备取正确的xib。

使用大小类，如果你想为iPhone和iPad创建一个单独的xib，如果视图足够简单，可以移植到iPhone和iPad。

在iOS设备和iOS模拟器上测试时，有一个小问题。看起来模拟器(XCode 6.0.1)在[[UIScreen mainScreen] bounds]中给出了宽度和高度的切换值。大小，取决于设备方向。

因此，在确定正确的物理屏幕尺寸时，这可能是一个问题。此代码还有助于区分所有2014年。iPhone型号:

iPhone4s iPhone5(和iPhone5s) iPhone6(及iPhone6+)

它也可以很容易地改变，使区别，如iPhone6从iPhone6+。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    CGSize iOSDeviceScreenSize = [[UIScreen mainScreen] bounds].size;

    if ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPhone)
    {
        if (iOSDeviceScreenSize.width > 568 || // for iOS devices
            iOSDeviceScreenSize.height > 568) // for iOS simulator
        {   // iPhone 6 and iPhone 6+

            // Instantiate a new storyboard object using the storyboard file named Storyboard_iPhone6
            storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard_iPhone6" bundle:nil];

            NSLog(@"loaded iPhone6 Storyboard");
        }
        else if (iOSDeviceScreenSize.width == 568 || // for iOS devices
                 iOSDeviceScreenSize.height == 568) // for iOS simulator
        {   // iPhone 5 and iPod Touch 5th generation: 4 inch screen (diagonally measured)

            // Instantiate a new storyboard object using the storyboard file named Storyboard_iPhone5
            storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard_iPhone5" bundle:nil];

            NSLog(@"loaded iPhone5 Storyboard");
        }
        else
        {   // iPhone 3GS, 4, and 4S and iPod Touch 3rd and 4th generation: 3.5 inch screen (diagonally measured)

                // Instantiate a new storyboard object using the storyboard file named Storyboard_iPhone4
            storyboard = [UIStoryboard story    boardWithName:@"MainStoryboard_iPhone" bundle:nil];

                NSLog(@"loaded iPhone4 Storyboard");
        }
    }
    else if ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad)
    {   // The iOS device = iPad

        storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard_iPadnew" bundle:nil];

        NSLog(@"loaded iPad Storyboard");
    }

    // rest my code
}

Download and install latest version of Xcode. Set a Launch Screen File for your app (in the general tab of your target settings). This is how you get to use the full size of any screen, including iPad split view sizes in iOS 9. Test your app, and hopefully do nothing else, since everything should work magically if you had set auto resizing masks properly, or used Auto Layout. If you didn't, adjust your view layouts, preferably with Auto Layout. If there is something you have to do for the larger screens specifically, then it looks like you have to check height of [[UIScreen mainScreen] bounds] as there seems to be no specific API for that. As of iOS 8 there are also size classes that abstract screen sizes into regular or compact vertically and horizontally and are recommended way to adapt your UI.

你可以添加以下代码:

if(UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone){
        if ([[UIScreen mainScreen] respondsToSelector: @selector(scale)]) {
            CGSize result = [[UIScreen mainScreen] bounds].size;
            CGFloat scale = [UIScreen mainScreen].scale;
            result = CGSizeMake(result.width * scale, result.height * scale);

            if(result.height == 960) {
                NSLog(@"iPhone 4 Resolution");
            }
            if(result.height == 1136) {
              NSLog(@"iPhone 5 Resolution");
            }
        }
        else{
            NSLog(@"Standard Resolution");
        }
    }

如果你需要将一个已经存在的应用程序转换为通用，你需要选择相应的xib文件->show Utilities-> show Size inspector。

在大小检查器中，你可以看到自动调整大小，通过使用这个工具你可以转换到现有的iOS应用程序。