"Blank screen" issue when updating your app for iOS 4 compatibility
The other day, we were updating our apps to make them compatible for iOS 4. And by "compatible" I mean just compiling them with the iOS 4 SDK so that they get some fast-app switching love.
What was weird though, was when running certain apps on the device, it launched with just a blank black screen. The console showed no errors, and the app didn't fault in any way. It was as if the view didn't load at all. Turns out iOS 4 requires a single line of code in the -applicationDidFinishLaunching: method to make the view visible - this wasn't the case previously.
I'm not sure in which version of the SDK this crept in, but when creating an iOS app using the UITabBar template in XCode, there is no [window makeKeyAndVisible] call. This didn't matter in previous versions of the SDK, but it does now.
[TL;DR] So, if your app starts with a blank black screen, just check if it calls [window makeKeyAndVisible] in your -applicationDidFinishLaunching: method (usually it's the last line). If it doesn't, add it in and the world will once again be safe. For now.
