修改UIButton不同状态下的图片

参考代码：

UIButton *bt  = [[UIButton alloc] init];

[bt setBackgroundImage:[UIImage imageNamed:@"scenic_spots_background_focused.png"] forState:UIControlStateNormal];

[bt setBackgroundImage:[UIImage imageNamed:@"scenic_spots_background_pressed.png"] forState:UIControlStateHighlighted];

THE  END!