总结：当button的状态为selected的时候，高亮时对应的状态应该是selected|highlighted，这与normal下高亮的状态highlighted不同。
以下是stackover上的提问，附上：
I've a UIButton and I set it with:
UIButton *myButton = [UIButton buttonWithType:UIButtonTypeCustom];
UIImage *imageNormal = [UIImage imageNamed:@"normal.png"];
UIImage *imageNormalHover = [UIImage imageNamed:@"normalHover.png"];
UIImage *imageSelected = [UIImage imageNamed:@"selected.png"];
UIImage *imageSelectedHover = [UIImage imageNamed:@"selectedHover.png"];
[myButton setImage:imageNormal forState:UIControlStateNormal];
[myButton setImage:imageSelected forState:UIControlStateSelected];
if (boolVar) {
[myButton setSelected:YES];
[myButton setImage:imageSelectedHover forState:UIControlStateHighlighted];
} else {
[myButton setImage:imageNormalHover forState:UIControlStateHighlighted];
}
The issue is when the state is normal and I try to press the button I see correctly the image normalHover.png but when the state is selected and I try to press the button I see still normalHover.png and not the selectedHover.png. It seems that with UIButton I'm unable to change the highlighted image. Do you how to solve?
Answer：
You need to set the image for the UIControlStateSelected | UIControlStateHighlighted combined state:
[myButton setImage:imageSelectedHover forState:(UIControlStateSelected | UIControlStateHighlighted)];
Because both states are on when the button is selected and you hignlight it by tapping on it.
（uibutton选中状态和高亮状态的区别：选中可以常态，高亮状态在Down才有效，up时候状态无效）－－－－按下未抬起时为高亮状态
