iOS导航BarButtonItem文字或者图片与屏幕边界的间隔

在设置navigationItem的leftBarButtonItem或rightBarButtonItem时，
用CustomView初始化UIBarButtonItem，不论怎么设置CustomView的frame，
添加到导航条上之后总是和屏幕边界有一定的间距（5pix），
如何自由调整这个间距呢？

下面介绍两种方法：
1、不用直接设置rightBartButtonItem而是设置rightBartButtonItems，并且第一个item设置为一个占位。

• (UIButton *)addRightItemWithTitle:(NSString *)title action:(SEL)action {
  UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
  CGSize size = [title sizeWithFont:[UIFont systemFontOfSize:16]];

  //! 这里需要根据内容大小来调整宽度
  button.frame = CGRectMake(0, 0, size.width <= 10 ? 70 : size.width + 10, 44);
  button.titleLabel.textColor = [UIColor whiteColor];
  button.titleLabel.font = [UIFont systemFontOfSize:16];
  button.titleLabel.textAlignment = NSTextAlignmentRight;
  [button setTitle:title forState:UIControlStateNormal];
  /**

  • 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-15时，间距正好调整
  • 为10；width为正数时，正好相反，相当于往左移动width数值个像素
    */
    UIBarButtonItem *negativeSpacer = [[UIBarButtonItem alloc]
    initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace
    target:nil action:nil];
    negativeSpacer.width = -15;

  [button addTarget:self action:action forControlEvents:UIControlEventTouchUpInside];
  UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithCustomView:button];
  self.navigationItem.rightBarButtonItems = @[negativeSpacer, backItem];
  return button;
  }

2、如果是只有图片，那么通过设置
[button setImageEdgeInsets:UIEdgeInsetsMake(0, -15, 0, -15)];这样也可以调整

• (UIButton *)addRightItemWithImage:(NSString *)imageName action:(SEL)action {
  UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
  UIImage *image = [UIImage imageNamed:imageName];
  button.frame = CGRectMake(0, 0, image.size.width, image.size.height);

  // 这里需要注意：由于是想让图片右移，所以left需要设置为正，right需要设置为负。正在是相反的。
  // 让按钮图片右移15
  [button setImageEdgeInsets:UIEdgeInsetsMake(0, 15, 0, -15)];

  [button setImage:image forState:UIControlStateNormal];
  [button addTarget:self action:action forControlEvents:UIControlEventTouchUpInside];
  button.titleLabel.font = [UIFont systemFontOfSize:16];
  UIBarButtonItem *rightItem = [[UIBarButtonItem alloc] initWithCustomView:button];
  self.navigationItem.rightBarButtonItem = rightItem;
  return button;
  }