I just tested my first Flex mobile app on iPhone 5, but as I was assuming it doesn't fit to the new 4" screen. Does anybody know if this is already possible? (using Flex 4.6 SDK)
This is a little goofy, but it works. First, make sure you've got the latest AIR SDK installed in your Flash Builder eclipse plug in directory. That will make sure that the following trick actually works.
Now, go to your projects main MXML file (if you're building a view based project that will be a ViewNavigatorApplication class instance). In the opening ViewNavigatorApplication tag place a property for splashScreenImage with a value of "@Embed('Default-568h@2x.png')". It should look something like this…
<s:ViewNavigatorApplication xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
firstView="views.myFirstView"
splashScreenImage="@Embed('Default-568h@2x.png')">
Now, make a 640w x 1136h splash screen png and name it "Default-568h@2x.png". Place that image file in the root (probably your "src" directory) of your project. Compile for your iPhone 5 target and voila!
It turns out that AIR looks for that larger splash screen file as an indicator that you're targeting an iPhone 5 screen size. No setting in the app.xml file. No property in code. Just that splashScreenImage file name.
THAT'S obvious, huh?
As far as creating different layouts for different screen sizes Rich Tretola has a great and cheap book, iOS Applications with Flex 4.5, that discusses responsive design using @media queries. His website has an excerpt that might help… but the book is cheap, useful and quick to read.