iOS11下自定义leftBarButtonItem大小改变的问题修复

iOS11下，leftBarButtonItem异常情况

一般leftBarButtonItem加载网络图片或因为其他问题，必须要在leftBarButtonItem使用自定义的UIButton时，就会因为图片太大，导致设置为UIButton的背景图片时，因为图片太大，拉宽leftBarButtonItem。如下图：

被拉宽的leftBarButtonItem

原始的方法为xib文件或者是自定义的：

UIButton *leftCustomButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 35, 35)];

[leftCustomButton setBackgroundImage:[UIImage imageNamed:@"defaultImage"] forState:UIControlStateNormal];

UIBarButtonItem * leftButtonItem =[[UIBarButtonItem alloc] initWithCustomView:leftCustomButton];

self.navigationItem.leftBarButtonItems = @[self.headerIconItem];

但是直接设置UIButton的frame在iOS 11下是没有作用的，解决方法如下：

  UIButton *leftCustomButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 35, 35)];

  [leftCustomButton setBackgroundImage:[UIImage imageNamed:@"defaultImage"] forState:UIControlStateNormal];

  UIView *leftCustomView = [[UIView alloc] initWithFrame: leftCustomButton.frame];

   [leftCustomView addSubview: leftCustomButton];
UIBarButtonItem * leftButtonItem =[[UIBarButtonItem alloc] initWithCustomView: leftCustomView];

  self.navigationItem.leftBarButtonItems = @[self.headerIconItem];

即在UIButton上在包装一层UIView，即可实现修改leftBarButtonItem的大小。
修改之后如下图：

正常大小的leftBarButtonItem