IOS:
UIBarButtonItem * searchBtnItem = [[UIBarButtonItem alloc]initWithCustomView:_searchButton];
UIBarButtonItem *negativeSpacer = [[UIBarButtonItem alloc]
initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace
target:nil action:nil];
/**
* width为负数时,相当于btn向右移动width数值个像素,由于按钮本身和边界间距为5pix,所以width设为-5时,间距正好调整
* 为0;width为正数时,正好相反,相当于往左移动width数值个像素
*/
negativeSpacer.width = -16;
self.navigationItem.rightBarButtonItems= [NSArray arrayWithObjects:negativeSpacer,searchBtnItem, nil];
SWIFT: