iOS 将UISegmentedController添加到导航栏中间

 //创建
    self.segmented =[[UISegmentedControl alloc]initWithItems:@[@"推荐阅读",@"我的订阅"]];
    //设置大小
    _segmented.frame = CGRectMake(0.0, 0.0, 200, 30.0);
    
    //设置默认选中
    _segmented.selectedSegmentIndex=0;
    
    //设置颜色
    _segmented.tintColor = [UIColor grayColor];
    
    //添加事件
    [_segmented addTarget:self action:@selector(changeView:) forControlEvents:UIControlEventValueChanged];
    
    [self.navigationItem setTitleView:_segmented];