解决导航条上自定义按钮不能靠左或靠右的问题

 _newsBtn = [UIButton buttonWithType:UIButtonTypeCustom];

    [_newsBtn setImage:[UIImage imageNamed:@"home_news"] forState:UIControlStateNormal];

    _newsBtn.frame = CGRectMake(0, 0, 30, 30);

    [_newsBtn addTarget:self action:@selector(newsbtnSysClike) forControlEvents:UIControlEventTouchUpInside];

    //用于把自定义的按钮与导航条的联系起来

    UIBarButtonItem *newsBtnItem = [[UIBarButtonItem alloc]initWithCustomView:_newsBtn];

    self.navigationItem.leftBarButtonItem = newsBtnItem;

    //解决按钮不靠左 靠右的问题.

    UIBarButtonItem *nagetiveSpacer = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace

                                                                                   target:nil action:nil];

    nagetiveSpacer.width = -10;//这个值可以根据自己需要自己调整

    self.navigationItem.leftBarButtonItems = @[nagetiveSpacer, newsBtnItem];