导航栏左右按钮 如何调左右距离

 UIView *rightView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 44, 44)];
    UIButton *settingButton = [UIButton buttonWithType:UIButtonTypeCustom];
    settingButton.frame = CGRectMake(17, 0, 44, 44);
    [settingButton addTarget:self action:@selector(settingAction:) forControlEvents:UIControlEventTouchUpInside];
    [settingButton setImage:[UIImage imageNamed:@"btn_setting"] forState:UIControlStateNormal];
    [rightView addSubview:settingButton];
     self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:rightView];