问题
I have a UIToolbar on the bottom of my app. On any device iPhone 5 and up it shows up correctly. On iPhone 4s and down it does not show on the screen at all. I have tried to add constraints but it is not helping. I am at a lose as to why this is happening. My app worked fine up until today. Any suggestions would be much appreciated.
来源：https://stackoverflow.com/questions/26004349/uitoolbar-not-displaying-on-iphone-4-and-iphone-4s