How can i instantiate a MvxTableViewController directly? - ios

Question

I want to show a UIPopoverController by clicking on a UIBarButtonItem on the Navigation bar. This UIPopoverController needs a "ContentViewController", that would be a MvxTableViewController with some data-binding. The problem is, if I instantiate some class derived from MvxTableViewController directly - instead of doing ShowViewModel<blah>(), I got an exception on "base.ViewDidLoad" on the overriden method ViewDidLoad.
What am I missing?
Thanks in advance!
EDIT:
If i use, for instance, a MvxViewController with an UITableView:
public class Test : MvxViewController
{
public override void ViewDidLoad()
{
View = new UIView() { BackgroundColor = UIColor.White };
//TableView = new UITableView(new RectangleF(0, 0, 300, 300));
base.ViewDidLoad();
var table = new UITableView(new RectangleF(0, 0, 300, 300));
// ios7 layout
if (RespondsToSelector(new Selector("edgesForExtendedLayout")))
EdgesForExtendedLayout = UIRectEdge.None;
var source = new MvxStandardTableViewSource(table, "TitleText Nome");
table.Source = source;
var set = this.CreateBindingSet<Test, Core.ViewModels.FirstViewModel>();
set.Bind(source).To(vm => vm.Distritos);
set.Apply();
table.ReloadData();
}
}
And if i have, on FirstViewModel's ViewDidLoad, during the construction of a Navigation Bar:
var buttonLocalizacao = new UIBarButtonItem("Localização", UIBarButtonItemStyle.Plain, (s, e) => {
distritoViewController = new Test();
nc = new UINavigationController(distritoViewController);
var distritoPopOver = new UIPopoverController(nc);
distritoPopOver.ContentViewController = nc;
distritoPopOver.PopoverContentSize = new SizeF(300, 300);
distritoPopOver.PresentFromBarButtonItem((UIBarButtonItem)s, UIPopoverArrowDirection.Up, true);
});
Everytime i hit the UIBarButtonItem "Localização" i get an exception on Test's "base.ViewDidLoad". Does this make sense?
EDIT 2:
This is the exception i receive:
"Unhandled Exception:
System.NullReferenceException: Object reference not set to an instance of an object
at Cirrious.MvvmCross.ViewModels.MvxViewModelLoader.LoadViewModel (Cirrious.MvvmCross.ViewModels.MvxViewModelRequest request, IMvxBundle savedState) [0x00000] in :0
at Cirrious.MvvmCross.Touch.Views.MvxViewControllerExtensionMethods.LoadViewModel (IMvxTouchView touchView) [0x00000] in :0
at Cirrious.MvvmCross.Touch.Views.MvxViewControllerExtensionMethods+<>c__DisplayClass1.b__0 () [0x00000] in :0
at Cirrious.MvvmCross.Views.MvxViewExtensionMethods.OnViewCreate (IMvxView view, System.Func`1 viewModelLoader) [0x00000] in :0
at Cirrious.MvvmCross.Touch.Views.MvxViewControllerExtensionMethods.OnViewCreate (IMvxTouchView touchView) [0x00000] in :0
at Cirrious.MvvmCross.Touch.Views.MvxViewControllerAdapter.HandleViewDidLoadCalled (System.Object sender, System.EventArgs e) [0x00000] in :0 "

Answer 1

Finally got it:
Instead of:
var buttonLocalizacao = new UIBarButtonItem("Localização", UIBarButtonItemStyle.Plain, (s, e) => {
distritoViewController = new Test();
nc = new UINavigationController(distritoViewController);
var distritoPopOver = new UIPopoverController(nc);
distritoPopOver.ContentViewController = nc;
distritoPopOver.PopoverContentSize = new SizeF(300, 300);
distritoPopOver.PresentFromBarButtonItem((UIBarButtonItem)s, UIPopoverArrowDirection.Up, true);
});
I had to create a distinct ViewModel to hold my MvxTableViewController (each MvxTableViewController, or MvxViewController, demands a corresponding ViewModel?), meaning, i could not bind "Test", that is a MvxTableViewController, to another, different, ViewModel (FirstViewModel for instance). "Test" must have a ViewModel of it's own.
So, eventually the corresponding ViewModel must be instantiated previously, and only after that can we instantiate the MvxTableViewController using "CreateViewControllerFor". Replacing the above "Test" for "DistritoViewModel", the rest is straightforward:
var buttonLocalizacao = new UIBarButtonItem("Localização", UIBarButtonItemStyle.Plain, (s, e) => {
if (distritoPopOver == null)
{
var viewModel = new DistritoViewModel();
var secondv = this.CreateViewControllerFor(viewModel) as MvxTableViewController;
nc = new UINavigationController(secondv);
distritoPopOver = new UIPopoverController(nc);
distritoPopOver.PopoverContentSize = new SizeF(300, 300);
}
distritoPopOver.PresentFromBarButtonItem((UIBarButtonItem)s, UIPopoverArrowDirection.Up, true);
});
Keep in mind: the variable distritoPopover, that holds the UIPopoverController, must be a class variable, or instantiated outside the Action in UIBarButtonItem, otherwise it will be garbage collected and cause an immediate crash after display!
Thanks everyone for the tips :)