I'm sure I set right images for different states. But the UIButtons looks not good. Like this:

[![enter image description here](https://i.stack.imgur.com/Al36f.png)](https://i.stack.imgur.com/Al36f.png)

[![enter image description here](https://i.stack.imgur.com/XqNuW.png)](https://i.stack.imgur.com/XqNuW.png)

Anyone knows why? Many thanks in advance!