UIButton 的EdgeInsets

UIButton默认有TitilLable 和 ImageView 组成。
默认现实风格：

UIButton默认风格

但是有时候，我们想文字在左边，图标在右边。又有时候图片在上面文字在下面居中现实。

UIButton居中现实

UIButton文字左边

代码：

    
    UIButton *button = [[UIButton alloc]initWithFrame:CGRectMake(100, 100, 150, 130)];
    [button setImage:[UIImage imageNamed:@"dd_album"] forState:UIControlStateNormal];
    [button setTitle:[NSString stringWithFormat:@"相册"] forState:UIControlStateNormal];
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [self.view addSubview:button];
    
    button.titleLabel.backgroundColor = [UIColor greenColor];
    button.layer.cornerRadius = 1;
    button.layer.borderColor = [UIColor blackColor].CGColor;
    button.layer.borderWidth = 1;
    
    CGRect imageRect = button.imageView.frame;
    CGRect titleRect = button.titleLabel.frame;
   
//  居中现实
//  button.imageEdgeInsets = UIEdgeInsetsMake(-titleRect.size.height, titleRect.size.width, 0, 0);
//  button.titleEdgeInsets = UIEdgeInsetsMake(imageRect.size.height, -imageRect.size.width, 0, 0);

//  文字在左边，图在右边
    button.imageEdgeInsets = UIEdgeInsetsMake(0, titleRect.size.width, 0,-titleRect.size.width);
    button.titleEdgeInsets = UIEdgeInsetsMake(0, -imageRect.size.width, 0, imageRect.size.width);

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

设置的是分别和上边界，左边界，下边界，右边界的偏移量。