"Specified cast is not valid" when using SetOnItemSelectedListener of NavigationBarView about androidx

[jpobst]

This looks like the line that is causing the InvalidCastException:

__args [0] = new JniArgumentValue ((listener == null) ? IntPtr.Zero : ((global::Java.Lang.Object) listener).Handle);

My guess is your implementation of NavigationBarView.IOnItemSelectedListener does not inherit from Java.Lang.Object, which is required.

[gmck]

@genis-bosch-ypsomed

The following is a cut-down version that I’ve been using with X.A, Net7 and Net8. See any of the NavigationGraph examples at https://github.com/gmck for more details. I'm using Xamarin.Google.Android.Material 1.10.0.3.

I'm pretty sure it changed from the original implementation a couple of years back, but I now can't remember what the old way was.

NavigationBarView.IOnItemSelectedListener

bottomNavigationView!.ItemSelected += BottomNavigationView_ItemSelected!;

private void BottomNavigationView_ItemSelected(object sender, NavigationBarView.ItemSelectedEventArgs e)
{
…
... navController!.Navigate(e.Item.ItemId, null, navOptions);
}

[genis-bosch-ypsomed]

Thank you for your helpful answers. From what I see, we weren't using the Java.Lang.Object which should be the issue. I will try this one and come back for feedback.

[gmck]

@genis-bosch-ypsomed

What do you get when you right-click NavigationView.IOnNavigationItemSelectedListener and then go to Definition

Mine has JavaObject.

public interface IOnNavigationItemSelectedListener : IJavaObject, IDisposable, IJavaPeerable
{
    [Register("onNavigationItemSelected", "(Landroid/view/MenuItem;)Z", "GetOnNavigationItemSelected_Landroid_view_MenuItem_Handler:Google.Android.Material.Navigation.NavigationView/IOnNavigationItemSelectedListenerInvoker, Xamarin.Google.Android.Material")]
    bool OnNavigationItemSelected(IMenuItem menuItem);
}

Does your main activity inherit from AppCompatActivity?

[gmck]

@genis-bosch-ypsomed

I had a bit of a brain fade last night when I posted the above. The above should have been about NavigationBarView.IOnItemSelectedListener, not NavigationView.

It should have read right-click on NavigationBarView.IOnItemSelectedListener

[Register("com/google/android/material/navigation/NavigationBarView$OnItemSelectedListener", "", "Google.Android.Material.Navigation.NavigationBarView/IOnItemSelectedListenerInvoker")]
public interface IOnItemSelectedListener : IJavaObject, IDisposable, IJavaPeerable
{
    [Register("onNavigationItemSelected", "(Landroid/view/MenuItem;)Z", "GetOnNavigationItemSelected_Landroid_view_MenuItem_Handler:Google.Android.Material.Navigation.NavigationBarView/IOnItemSelectedListenerInvoker, Xamarin.Google.Android.Material")]
    bool OnNavigationItemSelected(IMenuItem p0);
}

If you look at the IOnItemSelectedListenerInvoker below that, you'll see it inherits from Java.Lang.Object. If I remember correctly the change I referred to was introduced in Material 1.4.0

[genis-bosch-ypsomed]

Thanks @gmck and @jpobst, both solutions worked. We ended using the ItemSelected event as it allows us to directly work on the handler without the need of a new class. I will close this issue.