braventit / litemvvmforms

LiteMVVMForms, a very simple framework for Xamarin.Forms projects.

LiteMVVMForms

LiteMVVMForms, a very simple framework for Xamarin.Forms projects.

Principles:

• Not IoC implemented. Just a basic Service Locator is included LiteServiceLocator.
• Separate completaly the Views from the ViewModels with the static class ViewFactory.
• Navigation happens in the ViewModel.

Initial setup

Just install the nuget package Install-Package LiteMVVMForms in your PCL project.

Create 2 private functions to register services and Views in your Application Forms class as follows:

public partial class App : Application
     {
         private IViewFactory _viewFactory;
 
         public App ()
         {
             // Register the services in the Forms Service Locator
             RegisterServices ();
 
             // Register the ViewModels and asociate them to the corresponding Views
             RegisterViews ();
             
             InitializeComponent (); 
 
             // The root page of your application
             MainPage = new LiteNavigationPageService<FirstViewModel>().Create();
         }
 
         private void RegisterServices()
         {
             LiteServiceLocator.Current.Register<IMarvelApiService, MarvelApiService> ();
         }
 
         private void RegisterViews()
         {
            ViewFactory.Register<FirstViewModel, FirstView> ();
            ViewFactory.Register<DetailViewModel, DetailView> ();
         }
 
         protected override void OnStart ()
         {
             // Handle when your app starts
         }
 
         protected override void OnSleep ()
         {
             // Handle when your app sleeps
         }
 
         protected override void OnResume ()
         {
             // Handle when your app resumes
         }
             
     }

ViewFactory

The ViewFactory is the repository for ViewModels and Views.

The ViewFactory is a static class and this is how to register your ViewModels and Views:

private void RegisterViews()
{
    ViewFactory.Register<FirstViewModel, FirstView> ();
    ViewFactory.Register<DetailViewModel, DetailView> ();
}

LiteServiceLocator

This is a basic Service Locator. The reason of creating my own Service Locator and not to use DependencyService is because to use DependencyService you need to execute Forms.Init() and this is a bad choice if you want to have your Unit Tests in a nUnit Library Project. This is how to use it:

// Register
private void RegisterServices()
{
    LiteServiceLocator.Current.Register<IMarvelApiService, MarvelApiService> ();
}

// Resolve
private readonly IMarvelApiService _marvelService;
public FirstViewModel ()
{
     _marvelService = LiteServiceLocator.Current.Get<IMarvelApiService>();
}

ViewModels

The ViewModels have to inherit from ViewModelBase class in order to use them using LiteMVVMForms. Once we have done this we access the following capabilities:

• Navigation - Navigation Service implementation of Xamarin.Forms.

  • PopAsync
  • PopModalAsync
  • PushAsync
  • PushModalAsync
  • DisplayAlert
  • DisplayActionSheet

• InitAsync - You can override the InitAsync method of the ViewModelBase. This method is executed after the ViewModel constructor and before the View is displayed.

• View_Appearing - You can override this Event which is happening when the View in appearing.

• View_Disappering - You can override the disappering event of the View.

Example of how to use the Navigation at the ViewModel:

this.Navigation.PushAsync<DetailViewModel> (new DetailViewModel (character));

Lite Pages Services

To access manually to the ViewFactory, the MainPage initialization it's being done through a Page Services for ContentPages, NavigationPages and MasterDetailPages. These are: LiteNavigationPageService, LiteContentPageService and LiteMasterDetailPageService. My intention is to create new Page Services for Tab pages and Caruossel pages and will be available in future versions.

Enjoy!