UIBarButtonItem with custom view not properly aligned on iOS 7 when used as left or right navigation bar items

Works until iOS11!

You can use negative flexible spaces and rightBarButtonItems property instead of rightBarButtonItem:

UIBarButtonItem *spacer = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace target:nil action:nil];
spacer.width = -10; // for example shift right bar button to the right

self.navigationItem.rightBarButtonItems = @[spacer, yourBarButton];

In order to fix this bug, you must subclass UIButton so that you can override alignmentRectInsets. From my testing, you'll need to return a UIEdgeInsets with either a positive right offset or a positive left offset, depending on the button position. These numbers make no sense to me (at least one of them should be negative, according to common sense), but this is what actually works:

- (UIEdgeInsets)alignmentRectInsets {
    UIEdgeInsets insets;
    if (IF_ITS_A_LEFT_BUTTON) {
        insets = UIEdgeInsetsMake(0, 9.0f, 0, 0);
    } 
    else { // IF_ITS_A_RIGHT_BUTTON
        insets = UIEdgeInsetsMake(0, 0, 0, 9.0f);
    }
    return insets;
}

Special thanks to @zev for suggesting I try adjusting alignmentRectInsets.