A launch file (or image) provides a simple placeholder image that iOS displays when your app starts up. The placeholder image gives users the impression that your app is fast and responsive because it appears instantly and is quickly replaced by the first screen of your app. Every app must supply a launch file or at least one static image.
In iOS 8 and later, you can create a XIB or storyboard file instead of a static launch image. When you create a launch file in Interface Builder, you use size classes to define different layouts for different display environments and you use Auto Layout to make minor adjustments. Using size classes and Auto Layout means that you can create a single launch file that looks good on all devices and display environments. (For an overview of display environments and size classes, see Build In Adaptivity; to learn how to use size classes in Interface Builder, see Size Classes Design Help.)
If you also need to support earlier versions of iOS, you can continue to supply static launch images in addition to a launch file.
The following design guidelines apply to both launch files and static launch images.
Design a plain launch image that improves the user experience. In particular, the launch image isn’t an opportunity to provide:
An “app entry experience,” such as a splash screen
An About window
Branding elements, unless they are a static part of your app’s first screen
Because users are likely to switch among apps frequently, you should make every effort to cut launch time to a minimum, and you should design a launch image that downplays the experience rather than drawing attention to it.
Design a launch image that is identical to the first screen of the app, except for:
Text. The launch image is static, so any text you display in it won’t be localized.
UI elements that might change. If you include elements that might look different when the app finishes launching, users can experience an unpleasant flash between the launch image and the first app screen.
If you think that following these guidelines will result in a plain, boring launch image, you’re right. Remember, the launch image doesn’t provide you with an opportunity for artistic expression. It’s solely intended to enhance the user’s perception of your app as quick to launch and immediately ready for use. For example, Settings and Weather each supply a launch image that is little more than a background image.
The Settings launch image
The Weather launch image
If you need to use static launch images, you create images in different sizes for different devices. Static launch images for all devices must include the status bar region. For specific measurements, see Table 45-1.
Although it’s best to use a launch file for iPhone 6 and iPhone 6 Plus, you can instead supply static launch images if necessary. If you need to create static launch images for these devices, use the following sizes:
For iPhone 6:
750 x 1334 (@2x) for portrait
1334 x 750 (@2x) for landscape
For iPhone 6 Plus:
1242 x 2208 (@3x) for portrait
2208 x 1242 (@3x) for landscape