Providing launch images for AIR applications on iOS

According to the Apple iOS human interface guidelines, developers must provide at least one launch image for an iOS app.  For an enhanced user experience, however, Apple expects apps to have launch images for all supported devices and resolutions. 

This article covers the use of launch images with Adobe AIR applications on iOS.

In general, an iPhone application should have a portrait launch image, and an iPad application should have a launch image for both possible launch orientations of the application. As noted in Apple’s Custom Icon and Image Creation Guidelines, every application should include launch images for different sizes and resolutions. If you look at the sizes closely, you’ll notice that Apple expects full-screen launch images for iPhone, but non-full-screen launch images for iPad. This size recommendation does not depend on the app.

A launch image must be visible instantly when the user starts the application and must remain visible until the application is fully ready to use. For AIR applications, this means the launch image must remain visible until the AIR runtime is completed initialized. To achieve this, the AIR runtime displays the same launch image as shown by iOS until the app is completely ready to use. Recently, there were some instances in which launch images appeared to drift slightly during application launch. This occurred because Apple expected full-screen launch images for iPhone but not for iPad. The drift was due to image scaling when a full-screen launch image was displayed in a non-full-screen area (on iPhone) or a non-full-screen launch image in a full-screen area (on iPad).

To resolve these issues permanently, Adobe changed the guidelines for launch screen image sizes for iPad in AIR 3.4. In the new guidelines, all AIR applications for the iOS platform are expected to include only the full-screen launch images at the resolution of the supported device. This means that the expected image size of the default portrait image for a high resolution iPad would be 1536 × 2048 for AIR 3.4 onwards. This is true for full-screen and non-full-screen apps. The extra 40 pixels are hidden behind the status bar for non-full-screen apps.

Table 1 shows the expected launch image sizes for AIR applications on the iOS platform for AIR 3.4 and later.

Table 1. Launch image sizes for iOS devices.

For details on the file naming scheme used for launch images, see the iOS Launch Images section in Building Adobe AIR Applications.

For iPhone 5 append -568h to the launch image file name. For example, the default file would be Default-568h@2x.png. (The @2x is included for launch images intended for high-resolution retina displays). Non-retina mode is also supported on the iPhone 5. However, launch images should be packaged for the device, so even if you run an app in non-retina mode it is better to package the Default-568h@2x.png file and then use the non-retina resolution in the app.

Here are some resources on iOS launch images:

• Apple Custom Icon and Image Creation Guidelines
• Apple Launch Images documentation
• Adobe help on iOS launch images
• Deploying AIR Apps on iPhone 5