今天在cell上加了一个button，设了image
secondButton.buttonType = UIButtonTypeCustom;
[secondButton setImage:image_2 forState:UIControlStateNormal];
但是点击上去无高亮效果，经查找
发现两个问题
1、应该设backGroundImage
[secondButton setBackgroundImage:image_2 forState:UIControlStateNormal];
2、设置属性为YES
secondButton.showsTouchWhenHighlighted = YES;
修改了以上两点后，button就显示出高亮效果了。
