关于 UIEdgeInsets 的使用

UIEdgeInsets UIEdgeInsetsMake (
   CGFloat top,
   CGFloat left,
   CGFloat bottom,
   CGFloat right
);

    homeVC.tabBarItem.image = [UIImage imageNamed:@"sy_sy_b1.png"];
    homeVC.tabBarItem.selectedImage = [UIImage imageNamed:@"sy_sy_b2.png"];
    homeVC.tabBarItem.imageInsets = UIEdgeInsetsMake(8, 0, -8, 0);

调整 item 的图片位置 以及大小