CODEWITHSUNDEEP
c#objective-ciosxamarin.iosuiapplicationdelegate
Matt
Matt

Reputation: 1131

Get reference to UINavigationController

I have a rootcontroller pushed on a UINavigationController. Inside that rootcontroller class, I can access the UINavigationController with this.NavigationController

However, this rootcontroller has a ScrollView and I'm adding subcontrollers (or more precise, the View of this subcontroller) to this ScrollView.

I would now like to access the UINavigationController from inside such subcontroller. Following properties are all null

        this.NavigationController
        this.ParentViewController
        this.PresentedViewController
        this.PresentingViewController

It seems in ObjectiveC you can use following code

YourAppDelegate *del = (YourAppDelegate *)[UIApplication sharedApplication].delegate;
[del.navigationController pushViewController:nextViewController animated:YES];

Unfortunately, i don't know how to map this to C# in MonoTouch. I tried the following, but it's not working:

UIApplication.SharedApplication.KeyWindow.RootViewController.NavigationController

I know I could pass the UINavigationController object to all my classes (parameter in constructor), but that's probably not the cleanest way to go.

Upvotes: 3

Views: 900

Answers (2)

Dimitris Tavlikos
Dimitris Tavlikos

Reputation: 8170

To extend poupou's answer, here is an example of what I usually do in my AppDelegate class:

Add a static property of the AppDelegate itself:

public static AppDelegate Self { get; private set; }

Add my root navigation controller as a property:

public UINavigationController MainNavController { get; private set; }

In FinishedLaunching:

Self = this;
window = new UIWindow(UIScreen.MainScreen.Bounds);
this.MainNavController = new UINavigationController(); // pass the nav controller's root controller in the constructor
window.RootViewController = this.MainNavController;
// ..

This way, I can access the root view controller from anywhere, like this:

AppDelegate.Self.MainNavController.PushViewController(someViewController);

... instead of having to write this all the time:

AppDelegate myAppDelegate = (AppDelegate)UIApplication.SharedApplication.Delegate;
myAppDelegate.MainNavController.PushViewController(someViewController);

Plus, I can directly access all other AppDelegate's properties I might have.

Hope this helps.

Upvotes: 4

poupou
poupou

Reputation: 43553

UIApplicationDelegate does not, itself, define a navigationController property.

OTOH [UIApplication sharedApplication].delegate returns the instance of your own, application specific, UIApplicationDelegate - so it's a great place to share stuff (and why it's frequently used).

What commonly happens, in ObjectiveC, is that this custom ,UIApplicationDelegate-derived, type will implement it's own application-wise properties. IOW YourAppDelegate will implement a navigationController property that can be accessed, anywhere inside the app, by using [UIApplication sharedApplication].delegate.

You can do something very similar in .NET / C#. Simply add your own properties to your AppDelegate type, like this example. You'll be able to access them like Objective-C (if you like) or more directly (e.g. by making them public static properties).

Note that you still have to track and set your properties correctly (just like it needs to be done in Objective-C too).

Upvotes: 2

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