UIButton 点击后变灰

+(UIButton *)getBlueButtonWithTitle:(NSString *)aTitle{
    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
   //要使用系统的变灰，只需设置BackgroundImage即可
    [button setBackgroundImage:[UIImage imageNamed:@"blue.png"] forState:UIControlStateNormal];
    [button setTitle:aTitle forState:UIControlStateNormal];
  //变化后标题的颜色设置需设置状态为UIControlStateHighlighted
    [button setTitleColor:[UIColor lightGrayColor] forState:UIControlStateHighlighted];
    button.layer.cornerRadius = 5;
    button.layer.masksToBounds = YES;
    return button;
}