Xamarin NSNotificatioCenter: How can I get the NSO

问题:

I am trying to post a notification in a view from my app to another one using NSNotificationCenter. So in my destination class I create my observer as follows:

NSNotificationCenter.DefaultCenter.AddObserver ("ChangeLeftSide", delegate {ChangeLeftSide(null);});

and I have my method:

public void ChangeLeftSide (UIViewController vc)
{
    Console.WriteLine ("Change left side is being called");
}

Now from another UIViewController I am posting a notification as follows:

NSNotificationCenter.DefaultCenter.PostNotificationName("ChangeLeftSide", this);

How can I access the view controller that is being passed in my post notification in my destination class? In iOS it is very straight forward but I cannot seem to find my way in monotouch (Xamarin)...

回答1:

When you AddObserver, you want to do it in a slightly different way. Try the following:

NSNotificationCenter.DefaultCenter.AddObserver ("ChangeLeftSide", ChangeLeftSide);

and the declaration of your ChangeLeftSide method to conform to Action<NSNotification> expected by AddObserver - giving you the actual NSNotification object. :

public void ChangeLeftSide(NSNotification notification)
{
    Console.WriteLine("Change left side is being called by " + notification.Object.ToString());
}

So when you PostNotificationName, you're attaching the UIViewController object to the notification, which can be retrieved in your NSNotification via the Object property.

回答2:

I found the answer, here are the changes that need to be made on the code I posted in the question:

public void ChangeLeftSide (NSNotification notification)
{
    Console.WriteLine ("Change left side is being called");
    NSObject myObject = notification.Object;
    // here you can do whatever operation you need to do on the object
}

And the observer is created:

NSNotificationCenter.DefaultCenter.AddObserver ("ChangeLeftSide", ChangeLeftSide);

Now you can cast or type check the NSObject and do anything with it! Done!