如何在导航栏中添加页面指示器？

Question

像推特一样：

我在UITabBarController中有一个PageViewController，它又位于UINavigationController中。

有人能告诉我如何在导航栏中显示页面指示符吗？

Answer 1

编辑：我只是发现navigationController.viewControllers只包含堆栈。 我将在一分钟内发布一个编辑

编辑2：好吧，看来你必须事先知道视图控制器的数量。

也许不是最好的解决方案，但它对我有用。刚试过:)）

@interface ViewController () <UINavigationControllerDelegate>
@property (nonatomic, strong) UIPageControl *pageControl;
@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    UINavigationController *navController = self.navigationController;
    navController.delegate = self;

    navController.navigationBar.barTintColor = [UIColor colorWithRed:.2
                                                               green:.4
                                                                blue:.9
                                                               alpha:1];

    CGSize navBarSize = navController.navigationBar.bounds.size;
    CGPoint origin = CGPointMake( navBarSize.width/2, navBarSize.height/2 );

    self.pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake(origin.x, origin.y,
                                                                       0, 0)];

    //Or whatever number of viewcontrollers you have
    [self.pageControl setNumberOfPages:2];

    [navController.navigationBar addSubview:self.pageControl];

    navController.delegate = self;
}

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    int index = [navigationController.viewControllers indexOfObject:viewController];
    self.pageControl.currentPage = index;
}

@end

以下是一些截图。

Answer 2

这是寻找 Swift 解决方案的人的答案。

（根据自己的需要调整格式）

class NavigationControllerWithPageControl: UINavigationController, UINavigationControllerDelegate {

    let numberOfPages: Int

    init(rootViewController: UIViewController, numberOfPages: Int) {
        self.numberOfPages = numberOfPages
        super.init(rootViewController: rootViewController)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        delegate = self
        navigationBar.addSubview(pageControl)
        pageControl.centerXAnchor.constraint(equalTo: navigationBar.centerXAnchor).isActive = true
        pageControl.centerYAnchor.constraint(equalTo: navigationBar.centerYAnchor).isActive = true
    }

    lazy var pageControl: UIPageControl = {
        let navBarsize = navigationBar.bounds.size
        let origin = CGPoint(x: navBarsize.width/2, y: navBarsize.height/2)
        let pc = UIPageControl(frame: CGRect(x: origin.x, y: origin.y, width: 100, height: 20))
        pc.translatesAutoresizingMaskIntoConstraints = false
        pc.numberOfPages = numberOfPages
        pc.currentPageIndicatorTintColor = .black
        pc.pageIndicatorTintColor = UIColor.white//.withAlphaComponent(0.3)
        pc.isUserInteractionEnabled = false
        return pc
    }()

    func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
        let index = navigationController.viewControllers.firstIndex(of: viewController) ?? NSNotFound
        DispatchQueue.main.async { [weak self] in
            self?.pageControl.currentPage = index
            guard let pageControlSubviews = self?.pageControl.subviews.enumerated() else {return}
            for (_, dotView) in pageControlSubviews {
                dotView.transform = CGAffineTransform(scaleX: 1.3, y: 1.3)
                dotView.layer.borderColor = UIColor.black.cgColor
                dotView.layer.borderWidth = 1
            }
        }
    }

}

用法：

let navigationViewController = NavigationControllerWithPageControl(rootViewController: SomeViewController(), numberOfPages: 7)
present(navigationViewController, animated: true, completion: nil)