Question

有人可以解释一下为什么我想在任何地方获取NavigationController null，即使MvvmCross的Presenter类似乎初始化了一个吗？

Bellow是我目前的代码，我尝试了多种方法来获取NavigationController，但没有一种方法可以工作。

这样做的目的是将其隐藏在应用程序的第一个屏幕上（登录）。怎么做到这一点？

AppDelegate.cs

    [Register("AppDelegate")]
public class AppDelegate : MvxApplicationDelegate
{
    private UIWindow window;

    public override bool FinishedLaunching(UIApplication application, NSDictionary launchOptions)
    {
        window = new UIWindow(UIScreen.MainScreen.Bounds);
        var presenter = new MvxIosViewPresenter(this, window);

        var setup = new Setup(this, presenter);
        setup.Initialize();

        var startup = Mvx.Resolve<IMvxAppStart>();
        startup.Start();

        window.MakeKeyAndVisible();

        return true;
    }
}

LoginScreen.cs

public partial class LoginScreen : MvxViewController
{
    private UITabBarController tabBarController;

    public new LoginViewModel ViewModel
    {
        get { return (LoginViewModel)base.ViewModel; }
        set { base.ViewModel = value; }
    }

    public LoginScreen()
    {
        NavigationController.SetToolbarHidden(true, false);

        tabBarController = new UITabBarController();
        tabBarController.View.Frame = new CGRect(0, 0, View.Bounds.Width, 450);

        var tab1 = new UIViewController();
        tab1.Title = "tab1";
        tab1.View.BackgroundColor = UIColor.Green;
        var tab2 = new UIViewController();
        tab2.Title = "tab2";
        tab2.View.BackgroundColor = UIColor.Orange;
        var tab3 = new UIViewController();
        tab3.Title = "tab3";
        tab3.View.BackgroundColor = UIColor.Red;

        tabBarController.ViewControllers = new UIViewController[] { tab1, tab2, tab3 };

        var cgrect = new CGRect(0, 510, View.Bounds.Width, 45);
        var button = new UIButton(UIButtonType.Custom)
        {
            BackgroundColor = UIColor.Green,
        };
        button.SetTitle("click", UIControlState.Normal);
        button.Frame = cgrect;

        View.AddSubviews(new UIView[] { tabBarController.View, button });

        var swipeLeft = new UISwipeGestureRecognizer(HandleLeftSwipe)
        {
            Direction = UISwipeGestureRecognizerDirection.Left
        };
        var swipeRight = new UISwipeGestureRecognizer(HandleRightSwipe)
        {
            Direction = UISwipeGestureRecognizerDirection.Right
        };
        tabBarController.View.AddGestureRecognizer(swipeLeft);
        tabBarController.View.AddGestureRecognizer(swipeRight);
    }

Answer 1

构造函数中NavigationController属性为空的原因是因为它在生命周期的那一点没有附加到UINavigationViewController。

您最好在覆盖ViewDidLoad

的内部设置UI

NavigationController为null

1 个答案: