It has to deal with your auto-layout within Interface Builder I'm sure. IF you are making your view by using IB, then all you gotta do is click on the icon for your view controller, and then select all objects (command + a) and then just go to the icon that looks like this.
Click on the one that shows the ball, and there is an option within this that says "Clear Constraints in Container." Click on that option, and after you do that, there should be another option that says "Add Missing Constraints in Container." This will add default options as to the size based on your items in your view controller.
Then just run the device and I'm sure it has fixed it.
I hope this helps you!