有时候由于项目的需要我们需要自定义UIBarButtonItem，但是自定义的rightBarButtonItem 和leftBarButtonItem距离屏幕的距离往往不是我们想要的，下面是我在项目中的解决办法。

自定义的 UIBarButtonItem

 collectionBtn = [UIButton buttonWithType:UIButtonTypeCustom];
 [collectionBtn setImage:[UIImage imageNamed:@"collect"] forState:UIControlStateNormal];
 [collectionBtn setImage:[UIImage imageNamed:@"collect_focus"] forState:UIControlStateSelected];
 [collectionBtn addTarget:self action:@selector(collectionBtnClick:) forControlEvents:UIControlEventTouchUpInside];
 collectionBtn.frame = CGRectMake(0, 0, 50, 50);
 UIBarButtonItem *collectionView = [[UIBarButtonItem alloc]initWithCustomView:collectionBtn];
 UIBarButtonItem *rightPlaceHolderItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace target:nil action:nil];
//通过width指定宽度
 rightPlaceHolderItem.width = -15;
//placeHolder只有在数组的左边有效
 self.navigationItem.rightBarButtonItems = @[rightPlaceHolderItem,collectionView];

• 以上是rightBarButtonItem，leftBarButtonItem和这类似
• UIBarButtonSystemItem的类型常量中，UIBarButtonSystemItemFlexibleSpace ，UIBarButtonSystemItem不是按钮，它们是用来调整按钮间距用的对象，能设置指定宽度的BarButton