private void SavePageState(NavigationEntry entry)
{
// If the view model is IActivatable<,> then use this to save the page state
// NB: First check that the view has been created - this may still have state from a previous instance
// NB: Use reflection as we do not know the generic parameter types
if (entry.ViewLifetimeContext != null)
{
// Get the generic IActivatable<,> interface
object viewModel = entry.ViewLifetimeContext.ViewModel;
Type activatableInterface = ReflectionHelper.GetClosedGenericType(viewModel, typeof(IActivatable<,>));
if (activatableInterface != null)
{
// Save the state
MethodInfo saveStateMethod = activatableInterface.GetTypeInfo().GetDeclaredMethod("SaveState");
entry.State = saveStateMethod.Invoke(viewModel, null);
// Serialize the arguments and state
entry.SerializeData(activatableInterface.GenericTypeArguments[0], activatableInterface.GenericTypeArguments[1]);
}
}
}
private void DisplayPage(NavigationEntry entry)
{
// If the page and VM have not been created then do so
if (entry.ViewLifetimeContext == null)
CreatePage(entry);
// Navigate to the relevant page
navigationTarget.NavigateTo(entry.ViewLifetimeContext.View);
}
private void CallNavigatingFrom(NavigationEntry entry, NavigationMode navigationMode)
{
if (entry == null)
return;
object viewModel = entry.ViewLifetimeContext.ViewModel;
if (viewModel is INavigationAware)
((INavigationAware)viewModel).NavigatingFrom(navigationMode);
}
private void CreatePage(NavigationEntry entry)
{
// Create the View
IViewLifetimeContext viewLifetimeContext = viewFactory.CreateView(entry.PageName);
entry.ViewLifetimeContext = viewLifetimeContext;
// Activate the view model if it implements IActivatable<,>
// NB: Use reflection as we do not know the generic parameter types
object viewModel = entry.ViewLifetimeContext.ViewModel;
Type activatableInterface = ReflectionHelper.GetClosedGenericType(viewModel, typeof(IActivatable<,>));
if (activatableInterface != null)
{
// If required deserialize the arguments and state
entry.DeserializeData(activatableInterface.GenericTypeArguments[0], activatableInterface.GenericTypeArguments[1]);
// Activate the view model
MethodInfo activateMethod = activatableInterface.GetTypeInfo().GetDeclaredMethod("Activate");
activateMethod.Invoke(viewModel, new object[] { entry.Arguments, entry.State });
}
}
public void NavigateTo(string pageName, object arguments)
{
// Call NavigatingFrom on the existing navigation entry (if one exists)
CallNavigatingFrom(CurrentNavigationEntry, NavigationMode.New);
// Create the new navigation entry and push it onto the navigation stack
NavigationEntry navigationEntry = new NavigationEntry(pageName, arguments);
navigationStack.Push(navigationEntry);
// Navigate to the page
DisplayPage(navigationEntry);
// Call NavigatedTo on the new navigation entry
CallNavigatedTo(navigationEntry, NavigationMode.New);
}
