WP MVVM Navigation OnNavigatedTO - windows-phone-8

Question

I am starting to implement MVVM in my application and got an issue of knowing when the user navigated to the view.
To navigate between views, I can just use the navigationService.Navigate(...);
How do I check when I navigated to the view?
May I use the event navigationService.Navigated?
Is there no other method I can use like OnNavigatedTo that the page itself provide?

Answer 1

XAML:
xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
xmlns:cmd="clr-namespace:GalaSoft.MvvmLight.Command;assembly=GalaSoft.MvvmLight.Extras.WP71"
xmlns:toolkit="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone.Controls.Toolkit"
DataContext="{Binding titleSearchViewModel, Source={StaticResource Locator}}">
<i:Interaction.Triggers>
<i:EventTrigger>
<cmd:EventToCommand Command="{Binding PageLoaded, Mode=OneWay}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
VM:
private RelayCommand _PageLoaded;
public RelayCommand PageLoaded
{
get
{
if (_PageLoaded == null)
{
_PageLoaded = new RelayCommand(
() => Loaded()
);
}
return _PageLoaded;
}
}

Answer 2

In case this question is still actual, i prefer this solution: http://www.geoffhudik.com/tech/2010/10/10/another-wp7-navigation-approach-with-mvvm.html
If to use it, it is possible to send recipient ViewModel's parameters from the sender ViewModel:
SendNavigationMessage(Settings.NAVIGATION_PRODUCTS_SUBCATEGORIES,
new Dictionary<string, object> { { "SelectedIndex", Int32.Parse(item.id) } });
And receiver should define in xaml:
NavigatedToCommand="{Binding RefreshCommand}"
And then in receiver ViewModel:
public ICommand RefreshCommand // Should be set as NavigatedToCommand="{Binding RefreshCommand}" in xaml
{
get { return new RelayCommand(Refresh); }
}
public void Refresh()
{
_dataService.GetList(SelectedIndex, DownloadedCallback); // So, this would be called automatically after navigating is complete. SelectedIndex is updated at this moment.
}

Answer 3

Thanks for the answers provided. Both were helpful over a period of time until I decided to create a custom implementation of the navigation service that has been created by a few people.
I then made a contribution to the Cimbalino toolkit to suggest this and it has been introduced a while back.
I my personal opinion, that solves my issue the best. Have a look at the navigation service in there. The Navigated event pretty much solves my issue I had.
https://github.com/Cimbalino/Cimbalino-Toolkit
It basically comes down to this (in your viewmodel):
_navigationService.Navigated += OnNavigated;