Cannot show modal ViewController in iOS7

Question

I tried to show system defined viewcontrollers (MFMailComposeViewController, TWTweetComposeViewController,etc..) as a modal view.

But these viewcontrollers dosn\'t a

Answer 1

Turns out the issue only shows up when customizing UIBarButtons. If we use the following in our 32-bit app running on iPhone 5s, we have the problem:

[[UIBarButtonItem appearance] setTitlePositionAdjustment:UIOffsetMake(0, 1.0)
                                           forBarMetrics:UIBarMetricsDefault];

Leaving out that line works around the problem. We have filed a radar.