iOS - 修复iOS7以上自定义LeftBarbuttonItem后向右偏移

修复很简单: 

在自己定义的item前边加一个FixedSpace的BarButton.

UIBarButtonItem *negativeSpacer = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace target:nil action:nil]; 

negativeSpacer.width = -15;   

self.navigationItem.leftBarButtonItems = @[negativeSpacer, [[UIBarButtonItem alloc] initWithCustomView:button]];