Xamarin的iOS NavigationController返回null [英] Xamarin iOS NavigationController returns null

问题描述

我还在学习中Xamarin的ios的绳索，并已实现了基于下面的例子 MonoTouch的一侧抽屉.SlideoutNavigation 。在本教程中，有一个主视图控制器类，然后指定一个主导航控制器和侧面菜单。

I'm still learning the ropes in Xamarin ios and have implemented a side drawer based on the following example Monotouch.SlideoutNavigation. In this tutorial,there's a main view controller class which then assigns a main navigation controller and a side menu.

抽屉菜单选项被送入菜单类，而主屏幕/第一屏被传递到主导航控制器类，这是一个UINavigationController类的子类

The drawer menu options are fed into the menu class while the "home screen/first screen" is passed onto the main navigation controller class which is a subclass of a UINavigationController class.

我的主屏幕是一个tabcontroller类，我试图让这个类里面的导航控制器的引用，但它总是返回null。

My home screen is a tabcontroller class and I'm trying to make a reference to the navigation controller inside this class but it always returns null.

这是我面临着两个挑战：

These are the two challenges I'm facing:

• 导航控制器选项​​卡控制器和单个标签视图控制器里面总是空


• 我的个人标签控制器类的标题不会在导航栏上显示。

下面是在 AppDelegate类

[Register ("AppDelegate")]
public class AppDelegate : UIApplicationDelegate
{
        public SlideoutNavigationController Menu { get; private set; }

 public override bool FinishedLaunching (UIApplication application, NSDictionary launchOptions)
    {
                Menu = new SlideoutNavigationController ();

 var tabBarController = GetViewController (Main, "MainTabBarController");

                Menu.MainViewController = new MainNavigationController (tabBarController, Menu);
                Menu.MenuViewController = new MenuNavigationController (new MenuControllerLeft (), Menu) { NavigationBarHidden = true };
                SetRootViewController (Menu, false);

        return true;
    }
}

的MainTabController类

 public partial class MainTabBarController : UITabBarController
{
        UINavigationItem titleRequest,titleHome,titleSell;

  public MainTabBarController (IntPtr handle) : base (handle)
    {
  //Create an instance of our AppDelegate
         appDelegate = UIApplication.SharedApplication.Delegate as AppDelegate;

        //Get an instance of our Main.Storyboard
        var mainStoryboard = appDelegate.Main;

        var tab1 = appDelegate.GetViewController (mainStoryboard, "Tab1");

        var tab2 = appDelegate.GetViewController (mainStoryboard, "Tab2");

        var tab3 = appDelegate.GetViewController (mainStoryboard, "Tab3");


        var tabs = new UIViewController[] {
            tab1, tab2, tab3
        };

        this.SelectedIndex = 1;
        ViewControllers = tabs;
  }

  public override void ViewDidLoad ()
    {
        base.ViewDidLoad ();


            if(this.SelectedIndex == 0)
            {

                titleRequest = new UINavigationItem ("TAB 1");
                this.NavigationController.NavigationBar.PushNavigationItem (titleRequest, true); // NavigationController here is null

            }else if(this.SelectedIndex == 1)
            {
                titleHome = new UINavigationItem ("TAB 2");
                this.NavigationController.NavigationBar.PushNavigationItem (titleHome, true);


            }else{

                titleSell = new UINavigationItem ("TAB 3");
                this.NavigationController.NavigationBar.PushNavigationItem (titleSell, true);
            }

  }
 }

在主导航控制器类

 public class MainNavigationController : UINavigationController
{

 public MainNavigationController(UIViewController rootViewController, SlideoutNavigationController slideoutNavigationController)
        : this(rootViewController, slideoutNavigationController, 

            new UIBarButtonItem(UIImage.FromBundle("icon_sidemenu.png"), UIBarButtonItemStyle.Plain, (s, e) => {}))
    {
    }
  public MainNavigationController(UIViewController rootViewController, SlideoutNavigationController slideoutNavigationController, UIBarButtonItem openMenuButton)
        : base(rootViewController)
    {
        openMenuButton.Clicked += (s, e) => slideoutNavigationController.Open(true);
        rootViewController.NavigationItem.LeftBarButtonItem = openMenuButton;
    }

   public override void ViewDidLoad()
    {
        base.ViewDidLoad();
        this.Delegate = new NavigationControllerDelegate();
        InteractivePopGestureRecognizer.Enabled = true;

    }
   public override void PushViewController(UIViewController viewController, bool animated)
    {
        // To avoid corruption of the navigation stack during animations disabled the pop gesture
        if (InteractivePopGestureRecognizer != null)
            InteractivePopGestureRecognizer.Enabled = false;
        base.PushViewController(viewController, animated);
    }

    private class NavigationControllerDelegate : UINavigationControllerDelegate
    {
        public override void DidShowViewController(UINavigationController navigationController, UIViewController viewController, bool animated)
        {
            // Enable the gesture after the view has been shown
            navigationController.InteractivePopGestureRecognizer.Enabled = true;
        }
    }
}

修改 - 结果使得由Jason以下建议更改后

的

后imgur.com/AI7UY.jpgALT =标签消失
可能有人帮我看看有什么我做错了。

Could someone help me see what I'm doing wrong.

推荐答案

我终于找到了解决这个工作。对于使用Dillan的解决方案，并具有TabBarController类菜单类之一，这里就是我得到了它的工作的人。

I finally found a work around this. For anyone using Dillan's solution and has a TabBarController class as one of the Menu classes, here's how I got it to work.

1. 我从MainNavigationController类包裹TabBarController类在NavigationController，分开。我没有包裹在它自己的NavigationController每个选项卡this.That解决TabBarController类中的空引用到NavigationController后

1. I wrapped the TabBarController class in a NavigationController,apart from the MainNavigationController class. I didn't have to wrap each tab in it's own NavigationController after this.That solves the null reference to the NavigationController inside the TabBarController class

要解决的标题被遮蔽每个选项卡里面，我发现了一个简单的解决方案：

To solve the titles being obscured inside each tab, I found a simple solution:

public override void ViewDidLoad ()
{
    base.ViewDidLoad ();

    try{

            this.ViewControllerSelected += (object sender, UITabBarSelectionEventArgs e) => {

            switch(TabBar.SelectedItem.Title)
            {
            case"TAB 1" :

                Title = "TAB 1";
                break;

            case "TAB 2":   
              Title = "TAB 2";
                break;

            default:
                Title = "TAB 3";
                break;
            }
        };


    }catch(Exception e)
    {
        Console.WriteLine (e.Message);
    }
}

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