White screen when IOS opens the push Application

It runs normally on the simulator, but it is pushed to the real machine. After the push, the screen is white when the push application is opened. After the white screen is pushed, the screen is minimized and then clicked to display it normally.

After the white screen, the controls on the page can still be used, that is, invisible. If you pull the notification center from the top, you can see the page again. Let the notification center go back and change it to a white screen!
Strange!

This problem seems to be related to the main interface of the entry. This warning should appear at the same time when this problem occurs. "applications
Are expected to have a Root View Controller at the end of application launch ",

Here is a solution, which is implemented by adding mainwindow (the simulator is normal.

But ........

My solution is the opposite, because the program itself has mainwindow. XIB, And the configuration is correct,
It is a blank page. We do not need mainwindow after iOS 5. XIB, root viewcontroller is directly written in the finished function. I checked the project file-> Summary-> main interface. The return entry is mainwindow, but my root
View has nothing to do with it. In contrast to the previous project, the value of this place is directly empty, so the pipe section is left empty and run, and the problem is gone!

The specific reason is unclear,
My guess is that after the APP returns to the background, the reading entry (Value in summary) in the HC plist file is loaded with the wrong page because it is different from the defined root.