Xamarin.Forms.MVVMBase

Simple MVVM framework for Xamarin.Forms projects

This is the component, works on iOS, Android.

NuGet

Name	Info
Xamarin.Forms.MVVMBase

Platform Support

Xamarin.Forms.MVVMBase is a .NET Standard 2.0 library.Its dependencies are Xamarin.Forms and Microsoft Extensions for iOC

Initialize

App.cs :

 public partial class App : Application
    {
        public App()
        {
            InitializeComponent();
            BuildDependencies();
            InitNavigation();
        }

        public void BuildDependencies()
        {
           Container.Current.RegisterForNavigation<MainPage, MainViewModel>();

            //Configure Container
            Container.Current.Setup();
        }

        async void InitNavigation()
        {
               var navigationService = Container.Current.Resolve<INavigationService>();

            //Basic Startup
            await navigationService.InitializeAsync<MainViewModel>(null, true);
        }
    }

Determines which Initial ViewModel of your app :

InitializeAsync<MainViewModel>(null, true)

To register the View Matching ViewModel, use:

Container.Current.RegisterForNavigation <View, ViewModel> ();

Base ViewModel

BaseViewModel is based on all ViewModels. BaseViewModel Implements LoadAsync in addition to Navigation and Dialog Service

 public class MainViewModel : BaseViewModel
    {
       //Set Title
        public MainViewModel() : base("Main View")
        {
        }

        //Override Load
        public override async Task LoadAsync(NavigationParameters navigationData)
        {

        }

        //Override OnNavigate
        public override async Task OnNavigate(NavigationParameters navigationData)
        {
            if (navigationData.NavigationState == NavigationState.Backward)
            {
                //you can use the navigation to identify whether you have returned from a viewmodel
            }

            if (navigationData.NavigationState == NavigationState.Forward)
            {
                //you can use the navigation to identify whether you have navigated to a viewmodel
            }
        }
    }

BaseViewModel already behind the implementations of Title and isBusy by default to use in all views

Navigation

Use BaseViewModel NavigationService to navigate between them. You can also send parameters that will be received in LoadAsync.

await NavigationService.NavigateToAsync<DetalhesViewModel>();
await NavigationService.NavigateToAsync<DetalhesViewModel>(parameter);

NavigationParameters can be used to send parameters to a View, both when navigating to a new one and returning to the previous one.

  var parametros = new NavigationParameters();
  parametros.Add("key", value);

navigationData also returns if it is a new navigation or return from some view. use NavigationState :

 public enum NavigationState
    {
        Init, //Start App
        Forward, //Navigation to next View
        Backward // Return Navigation
    }

In addition to object navigation you can also browse via queryString as if using a url :

 NavigationParameters(string queryString)

Dialog

Use BaseViewModel DialogService to display custom alerts or an actionsheet.

 //Alert
 await DialogService.AlertAsync("Title", "Message", "Cancel Button Label");
 //Dialog
 await DialogService.AlertAsync("Title", "Message", "Accept Button Label", "Cancel Button Label");
 //ActionSheet
 await DialogService.ActionSheetAsync("Title", "Message", "Destruction Button Label", buttons);

BasePage

You can use BasePage instead of the standard ContentPage. BasePage automatically changes the title to that of BaseViewModel and also implements DeepLink

 /<?xml version="1.0" encoding="utf-8"?>
<base:BasePage   xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:base="clr-namespace:Xamarin.Forms.MVVMBase.Page;assembly=Xamarin.Forms.MVVMBase"
             mc:Ignorable="d">

</base:BasePage>

 public void OnAppLinkRequestReceived(Uri uri)

Dependency Injection

Xamarin.Forms.MVVMBase uses DryIoc. You can use your container in the app.cs with :

  Container.Current.Register<Interface, Implementation> (LifeTime.Singleton);

Use the lifetime for your IoC

public enum LifeTime
    {
        Scoped,
        Singleton,
        Transient
    }

For full Sample click here