MVX=0 WPF/Mac: A first MvvmCross Application (MVX+1 days of MvvmCross)

MVX=0 WPF/Mac: A first MvvmCross Application (MVX+1 days of MvvmCross)

Further to some feedback on the first couple of posts in the MVX+1 series (MVX=0, MVX=0F and MVX=1), I’ve gone back and added WPF and Mac support to the FirstDemo to show just how powerful MvvmCross is. I’ll cover very briefly here how to add these project types and then I’ll be updating the TipCalc post to include the basics for WPF and Mac setup in there too.

Let’s start with WPF:

  1. Add a WPF App (.NET Framework) called FirstDemo.Wpf
    image
  2. Add a reference to MvvmCross NuGet package
  3. Add reference to FirstDemo.Core project
  4. Add ProxyMvxApplication to App.xaml.cs
    public abstract class ProxyMvxApplication : MvxApplication<MvxWpfSetup<Core.App>, Core.App> { }
  5. Update App class in both App.xaml and App.xaml.cs to inherit from ProxyMvxApplication
  6. Remove all code in the App class (in App.xaml.cs) except for the constructor with call to InitializeComponent
    public App()
    {
         InitializeComponent();
    }
  7. Update MainWindow in both MainWindow.xaml and MainWindow.xaml.cs to inherit from MvxWindow
  8. Create Views folder
  9. Add new User Control (WPF) called FirstView.xaml
  10. Update FirstView in both FirstView.xaml and FirstView.xaml.cs to inherit from MvxWpfView
  11. Add XAML to FirstView.xaml
    <StackPanel Margin=”12,12,12,12″>
         <TextBox Text=”{Binding FirstName, Mode=TwoWay}”></TextBox>
         <TextBox Text=”{Binding LastName, Mode=TwoWay}”></TextBox>
         <TextBlock Text=”{Binding FullName}”></TextBlock>
    </StackPanel>

You should now be able to build and run the WPF application – notice how little code we have to add/change in order to get MvvmCross to work!

Next up is Mac which at the moment can only be done on a Mac (almost no surprises there – it’s the same as not being able to do UWP development on a Mac I guess):

  1. Add a Cocoa App called FirstDemo.Mac
    image
  2. Add a reference to MvvmCross NuGet package
  3. Add reference to FirstDemo.Core project
  4. At this point I would recommend unloading your project, editing the csproj file manually to removed the legacy nuget reference and add the following ItemGroup. Also remove the reference to package.config, remove the actual package.config file and delete both bin and obj folders. Reload the Mac project and force a rebuild.
    <ItemGroup>
       <PackageReference Include=”MvvmCross” Version=”6.0.0″ />
    </ItemGroup>
  5. Update AppDelegate to inherit from MvxApplicationDelegate
    [Register(“AppDelegate”)]
    public class AppDelegate: MvxApplicationDelegate<MvxMacSetup<App>, App>
    {
         public override void DidFinishLaunching(NSNotification notification)
         {
             MvxMacSetupSingleton.EnsureSingletonAvailable(this, MainWindow).EnsureInitialized();
             RunAppStart();
            // Due to a bug, do not call base DidFinishLaunching
             //base.DidFinishLaunching(notification);
         }
    }
    Note: There is a bug at the moment where if you don’t override DidFinishLaunching the application will crash on startup
  6. Open main.storyboard – this should open the storyboard in the XCode designer
  7. Select the existing view controller and set the Class and Storyboard ID to FirstView
    image
  8. Make sure the FirstView name change has been saved; return to VS for Mac and confirm that files FirstView.cs and FirstView.designer.cs have been created. If these have not been created, I would suggest doing a rebuild of your project to make sure the changes to the storyboard have been processed and the appropriate designer files created.
  9. From the Object Library drag two TextField and a Label across onto the design surface
    image
  10. Open Project navigator and make sure you have FirstView.h and FirstView.m. If you don’t I would suggest closing both XCode and VS for Mac, deleting the bin and obj folder from within the FirstDemo.Mac folder and reopening the solution in VS for Mac. Rebuild the Mac project and then launch XCode by double clicking on main.storyboard.
    image
  11. Hide both Project navigator (left pane) and Utilities (right pane) and show the Assistant Editor (the icon button that has linked circles in top right corner of XCode)
  12. From the navigator bar in the Assistant Editor, select Manual –> FirstView.Mac –> FirstView.h
    image
  13. Right-click on the first TextField
    image
  14. Click and drag the circle next to New Referencing Outlet across onto the FirstView.h immediately before the @End. When you release, you should be prompted to complete information about the new Outlet where you can specify the Name, textEditFirst, which will be the name of the backing variable you’ll be able to use to reference the TextField in code
    image
  15. Repeat the previous step for the second TextField, textEditSecond, and the Label, labelFull.
  16. Update FirstView.cs to add the MvxFromStoryboard attribute, change the base class to MvxViewController and add data binding using the CreateBindingSet extension
    [MvxFromStoryboard(“Main”)]
    public partial class FirstView : MvxViewController<FirstViewModel>
    {
         public FirstView(IntPtr handle) : base(handle)
         {
         }

  17.     public override void ViewDidLoad()
         {
             base.ViewDidLoad();
             var set = this.CreateBindingSet<FirstView, FirstViewModel>();
             set.Bind(textEditFirst).To(vm => vm.FirstName);
             set.Bind(textEditSecond).To(vm => vm.LastName);
             set.Bind(labelFull).To(vm => vm.FullName);
             set.Apply();
         }
    }

And there you have it – build and run your Mac FirstDemo application

    MvvmCross: Initialize method on the first view model

    MvvmCross: Initialize method on the first view model

    An issue was raised on MvvmCross following the release of v6 where applications were breaking because they have async code in the Initialize method of the first view model. Changes in v6 mean that the first view model is effectively loaded synchronously. This change was made because applications should not do heavy lifting before displaying the first view of their application as there are platform requirements that will cause the application to terminate if it doesn’t display the first view within the appropriate time window. This change means that any code that attempts to jump to a different thread (even something like Task.Delay) will cause the fist view of the application to break.

    In some scenarios this doesn’t make sense – for example if you have a splash screen Activity on Android, the first navigation can be done asynchronously because you already have a view being displayed on the screen. Here I’m going to use a simple example to demonstrate how to resolve this issue – you should only use this if you are using a splash screen for the first view of your application.

    Let’s start by breaking our application by adding the following to our first view model:

    public override async Task Initialize()
    {
         await Task.Delay(2000);
         await base.Initialize();
    }

    If you make this change and attempt to run your application you’ll see a black screen (on Android – and I’m using Android because we typically have a splash Activity such as in my earlier post).

    Next we’re going to fix this by overriding the MvxAppStart class to make the first navigation asynchronous:

    public class CustomMvxAppStart<TViewModel> : MvxAppStart<TViewModel>
         where TViewModel : IMvxViewModel
    {
         public CustomMvxAppStart(IMvxApplication application, IMvxNavigationService navigationService) : base(application, navigationService)
         {
         }


        protected override void NavigateToFirstViewModel(object hint)
         {
             NavigationService.Navigate<TViewModel>();
         }
    }

    Note that it’s the bold line that we’ve changed from the built in MvxAppStart class where we call NavigationService.Navigate<TViewModel>().GetAwaiter().GetResult(); which forces the navigation to be done synchronously.

    We now need to make sure that our CustomMvxAppStart is used. To do this we just need to change a single line in the App.cs to use RegisterCustomAppStart instead of RegisterAppStart

    RegisterCustomAppStart<CustomMvxAppStart<FirstViewModel>>();

    And we’re done – running the application now will allow the application to load successfully.

    MVX=1: TipCalc – a second example – adding IoC and the Xamarin Android Designer (MVX+1 days of MvvmCross)

    MVX=1: TipCalc – a second example – adding IoC and the Xamarin Android Designer (MVX+1 days of MvvmCross)

    Following on from the first post in the MVX+1 series, in this post we’ll create a basic Tip Calculator (mirroring the original post from the N+1 series). However, in this case the first section is a more detailed set of instructions on how to get the basics of all three platforms setup with MvvmCross. Going forward we’ll use this as a starting point so that we don’t need to cover over this in each subsequent post.

    Source code: https://github.com/nickrandolph/MvxPlus1DaysOfMvvmCross/tree/master/Mvx-01-TipCalc

    Getting Started Instructions (Native Apps)

    Note: In this case the name of the application is TipCalc but these instructions can be followed to get any new project started by simply replacing TipCalc with the name of your project.

    1. Create a the new solution by creating a new Class Library (.NET Standard) with the project name set to TipCalc.Core and the solution name to just TipCalc.
    2. Add a new project based on the Blank App (Universal Windows) project template called TipCalc.Uwp (make sure that the Minimum and Target versions are set to at least the Fall Creators Update)
    3. Add a new project based on the Android App (Xamarin) project template called TipCalc.Droid (use the Blank app template)
    4. Add a new project based on the iOS App (Xamarin) project template called TipCalc.iOS (use the Blank app template)
    5. Add a reference to MvvmCross NuGet package (v6.0.0 at time of writing to all four projects)
    6. TipCalc.Uwp: Update NuGet package Microsoft.NETCore.UniversalWindowsPlatform to the latest stable version (6.0.8 at time of writing)
    7. TipCalc.Droid: Update the Android version to Use Latest Platform (Project Properties –> Application –> Target Framework)
    8. TipCalc.Droid: Update Xamarin.Android.Support.Design to latest stable version (27.0.2 at time of writing)
    9. TipCalc.Droid: Add a reference to MvvmCross.Droid.Support.V7.AppCompat package
    10. TipCalc.iOS: Unload project; delete packages.config; edit TipCalc.iOS.csproj and add the following ItemGroup
      <ItemGroup>
         <PackageReference Include=”MvvmCross” Version=”6.0.0″ />
      </ItemGroup>

    11. Add a reference to TipCalc.Core to each of the three head projects (ie TipCalc.Uwp, TipCalc.Droid and TipCalc.iOS)
    12. TipCalc.Core: Rename the default Class1.cs to App.cs, and allow Visual Studio to rename class to App
    13. TipCalc.Core: Change the App class to inherit from MvxApplication
    14. TipCalc.Core: Add a folder, ViewModels, and add a class called FirstViewModel.
    15. TipCalc.Core: Change FirstViewModel to inherit from MvxViewModel
    16. TipCalc.Core: Override Initialize method in App to register services and set startup view model to FirstViewModel
      public override void Initialize()
      {
           CreatableTypes()
                   .EndingWith(“Service”)
                   .AsInterfaces()
                   .RegisterAsLazySingleton();
           RegisterAppStart<FirstViewModel>();
      }

    17. TipCalc.Uwp: Add a help class ProxyMvxApplication

      public abstract class ProxyMvxApplication: MvxApplication<MvxWindowsSetup<Core.App>, Core.App> { }
    18. TipCalc.Uwp: Change App.xaml and App.xaml.cs to inherit from ProxyMvxApplication
    19. TipCalc.Uwp: Remove all code in App.xaml.cs other than the constructor which should contain a single call to InitializeComponent
    20. TipCalc.Uwp: Delete MainPage.xaml and MainPage.xaml.cs
    21. TipCalc.Uwp: Add a Views folder, and  add a FirstView based on the Blank Page template
    22. TipCalc.Uwp: Change FirstView.xaml and FirstView.xaml.cs to inherit from MvxWindowsPage
    23. TipCalc.Droid: Add a new class, MainApplication, that inherits from MvxAppCompatApplication
    24. [Application]
      public class MainApplication : MvxAppCompatApplication<MvxAppCompatSetup<App>, App>
      {
           public MainApplication(IntPtr javaReference, JniHandleOwnership transfer) : base(javaReference, transfer)
           {
           }
      }

    25. TipCalc.Droid: Rename MainActivity.cs to SplashScreen.cs and let Visual Studio rename the class
    26. TipCalc.Droid: Rename activity_main.axml to SplashScreen.axml, and adjust layout to indicate application loading
    27. TipCalc.Droid: Adjust SplashScreen class to inherit from MvxSplashScreenAppCompatActivity and set NoHistory to true (since we don’t want the user to be able to press the back button and go back to the splash screen)

      [Activity(Label = “@string/app_name”, Theme = “@style/AppTheme”, MainLauncher = true, NoHistory = true)]
      public class SplashScreen : MvxSplashScreenAppCompatActivity

    28. TipCalc.Droid: Add a folder, Views, and add a new Activity, FirstView.c
    29. [Activity(Label = “FirstView”)]
      public class FirstView : MvxAppCompatActivity<FirstViewModel>
      {
           protected override void OnCreate(Bundle bundle)
           {
               base.OnCreate(bundle);


              SetContentView(Resource.Layout.FirstView);
           }
      }

    30. TipCalc.Droid: Add a new Android Layout to the Resources/Layout folder, FirstView.axml
    31. TipCalc.Droid: You may run into an error: “error XA4210: You need to add a reference to Mono.Android.Export.dll when you use ExportAttribute or ExportFieldAttribute.” If you do, you just need to Add Reference to Mono.Android.Export (search in the Add Reference dialog).
    32. TipCalc.iOS: Update AppDelegate class to inherit from MvxApplicationDelegate, and remove the default code.
      [Register(“AppDelegate”)]
      public class AppDelegate : MvxApplicationDelegate<MvxIosSetup<App>, App>
      {
      }
    33. TipCalc.iOS: Add an Empty Storyboard, called Main.storyboard, to the root of the project
    34. TipCalc.iOS: Add a ViewController to the Main.storyboard using the designer and set the Class and Storyboard ID to FirstView (also make sure the “User Storyboard ID” checkbox is set to true)
    35. TipCalc.iOS: Move the generated FirstView.cs and FirstView.designer.cs files (from the previous step) into a new folder called Views, and adjust the namespace of the FirstView class to FirstView.iOS.Views
    36. TipCalc.iOS: Update the FirstView class to inherit from MvxViewController
      [MvxFromStoryboard(“Main”)]
      public partial class FirstView : MvxViewController<FirstViewModel>

    Now to actually build out the Tip Calculator. Rather than embed the calculation logic into our view model, we’re going to abstract it out into a service. To do this we’ll make use of the IoC container made available by MvvmCross. We’ll register a CalculationService which will be injected into our view model constructor.

    Let’s continue our development of the Tip Calculator in TipCalc.Core:

    1. Add a folder called Services
    2. Add an interface ICalculationService into the Services folder
      public interface ICalculationService
      {
           double Tip(double subTotal, double generosity);
      }
    3. Add a class, CalculationService, which implements ICalculationService, again into the Services folder
      public class CalculationService : ICalculationService
      {
           public double Tip(double subTotal, double generosity)
           {
               return subTotal * generosity / 100.0;
           }
      }
    4. Add a constructor to the FirstViewModel which accepts an ICalculationService parameter
    5. private readonly ICalculationService _calculationService;
      public FirstViewModel(ICalculationService calculationService)
      {
           _calculationService = calculationService;
      }

    6. Add properties for SubTotal, Generosity, Tip and Total. Each property should take the following form where SetProperty is called within the setter
      private double _subTotal;
      public double SubTotal
      {
           get { return _subTotal; }
           set { SetProperty(ref _subTotal, value); }
      }
    7. Add a Recalc method which will invoke the Tip method on the ICalculationService
      private void Recalc()
      {
           Tip = _calculationService.Tip(SubTotal, Generosity);
           Total = SubTotal + Tip;
      }
    8. Add a call to Recalc into the setter for both SubTotal and Generosity
    9. Set some initial values for the SubTotal and Generosity (if you use the property setters, rather than setting the fields, the Recalc method will be invoked)

    That’s it for the core logic for the application. Now we just need to wire up the UI for each platform.

    One thing that’s worth noting is that in step 16 of the original setup where the Initialize method is overridden, there is logic in the Initialize method to interrogate the current assembly looking for all classes that end in Service and register them, based on their interface, with the MvvmCross IoC container – this is how MvvmCross knows about the implementation of the ICalculationService which is used when instantiating the FirstViewModel.

    Let’s built out the UWP interface in TipCalc.Uwp:

    1. Add the following XAML inside the existing Grid element:
      <StackPanel>
           <TextBlock Text=”SubTotal”/>
           <TextBox Text=”{Binding SubTotal, Mode=TwoWay}”/>
           <TextBlock Text=”How generous?”/>
           <Slider Value=”{Binding Generosity, Mode=TwoWay}”
                   Minimum=”0″
                   Maximum=”100″/>
           <TextBlock Text=”Tip:”/>
           <TextBlock Text=”{Binding Tip}”/>
           <TextBlock Text=”SubTotal:”/>
           <TextBlock Text=”{Binding Total}”/>
      </StackPanel>

    That’s the UWP interface done – four elements (with TextBlock headings): TextBox and Slider for inputting SubTotal and Generosity using two-way data binding, and two TextBlock for outputting the Tip and Total amounts.

    Now let’s do Android:

    1. Add the following namespace declaration to FirstView.axml
    2. Add the following xml to FirstView.axml
      <TextView
           android_text=”SubTotal”
           android_textAppearance=”?android:attr/textAppearanceMedium”
           android_layout_width=”fill_parent”
           android_layout_height=”wrap_content”
           android_id=”@+id/textView1″ />
      <EditText
           android_layout_width=”fill_parent”
           android_layout_height=”wrap_content”
           android_id=”@+id/editText1″
           local:MvxBind=”Text SubTotal” />
      <TextView
           android_text=”Generosity”
           android_textAppearance=”?android:attr/textAppearanceMedium”
           android_layout_width=”fill_parent”
           android_layout_height=”wrap_content”
           android_id=”@+id/textView2″ />
      <SeekBar
           android_layout_width=”fill_parent”
           android_layout_height=”wrap_content”
           local:MvxBind=”Progress Generosity”
           android_id=”@+id/seekBar1″ />
      <TextView
           android_text=”Tip”
           android_textAppearance=”?android:attr/textAppearanceMedium”
           android_layout_width=”fill_parent”
           android_layout_height=”wrap_content”
           android_id=”@+id/textView3″ />
      <TextView
           android_textAppearance=”?android:attr/textAppearanceMedium”
           android_layout_width=”fill_parent”
           android_layout_height=”wrap_content”
           local:MvxBind=”Text Tip”
           android_id=”@+id/textView4″ />
      <TextView
           android_text=”Total”
           android_textAppearance=”?android:attr/textAppearanceMedium”
           android_layout_width=”fill_parent”
           android_layout_height=”wrap_content”
           android_id=”@+id/textView5″ />
      <TextView
           android_textAppearance=”?android:attr/textAppearanceMedium”
           android_layout_width=”fill_parent”
           android_layout_height=”wrap_content”
           local:MvxBind=”Text Total”
           android_id=”@+id/textView6″ />

    In this case we’re leveraging the xml extensions offered by MvvmCross in order to do the data binding using the MvxBind syntax.

    Finally, let’s do iOS:

    1. Add the following code to the FirstView.cs
      public override void ViewDidLoad()
      {
           base.ViewDidLoad();

    2.     // Perform any additional setup after loading the view
           var label = new UILabel(new RectangleF(10, 0, 300, 40));
           label.Text = “SubTotal”;
           Add(label);


          var subTotalTextField = new UITextField(new RectangleF(10, 40, 300, 40));
           Add(subTotalTextField);


          var label2 = new UILabel(new RectangleF(10, 80, 300, 40));
           label2.Text = “Generosity?”;
           Add(label2);


          var slider = new UISlider(new RectangleF(10, 120, 300, 40));
           slider.MinValue = 0;
           slider.MaxValue = 100;
           Add(slider);


          var label3 = new UILabel(new RectangleF(10, 160, 300, 40));
           label3.Text = “Tip”;
           Add(label3);


          var tipLabel = new UILabel(new RectangleF(10, 200, 300, 40));
           Add(tipLabel);


          var label4 = new UILabel(new RectangleF(10, 240, 300, 40));
           label4.Text = “Total”;
           Add(label4);


          var totalLabel = new UILabel(new RectangleF(10, 280, 300, 40));
           Add(totalLabel);


         var set = this.CreateBindingSet<FirstView, FirstViewModel>();
           set.Bind(subTotalTextField).To(vm => vm.SubTotal);
           set.Bind(slider).To(vm => vm.Generosity);
           set.Bind(tipLabel).To(vm => vm.Tip);
           set.Bind(totalLabel).To(vm => vm.Total);
           set.Apply();

      }

    In this case for iOS we again make use of the data binding support provided by MvvmCross by using the CreateBindingSet method, followed by a call to Bind for each element property we want to bind, and then finally a call to Apply to complete the setup of data binding.

    And that’s it – a Tip Calculator for all three platforms.

    MVX=0F Side Note: Adding a Splash Screen

    MVX=0F Side Note: Adding a Splash Screen

    I received some feedback on my previous post on setting up MvvmCross for Xamarin.Forms, asking how to add a splash screen to the Android Forms application. In the post MVX=0 I converted the MainActivity that comes as part of the standard Xamarin Android project into a SplashScreen but when it came to the Android project for Xamarin.Forms I left it without a splash screen.

    Luckily adding a splash screen is really easy, so let’s add one to the Forms.Droid project:

    1. Copy the SplashScreen.axml from the /Resources/layout folder in the FirstDemo.Droid project into the /Resources/layout folder in the Forms.Droid project
    2. Remove “MainLauncher = true” from the Activity attribute on the MainActivity
    3. Change the MainActivity inheritance:
      public class MainActivity : MvxFormsAppCompatActivity<MainViewModel>

    4. Add a new class, SplashScreen.cs:
      [Activity(Label = “FirstDemo.Forms.Splash”, Theme = “@style/MainTheme”, MainLauncher = true, NoHistory = true)]
      public class SplashScreen : MvxFormsSplashScreenAppCompatActivity<MvxFormsAndroidSetup<Core.App, App>, Core.App, App>
      {
           public SplashScreen() : base(Resource.Layout.SplashScreen)
           {
           }

    5.     protected override void RunAppStart(Bundle bundle)
           {
               StartActivity(typeof(MainActivity));
               base.RunAppStart(bundle);
           }
      }

    And there you have it – the Android Xamarin.Forms project will launch with a splash screen before redirecting to the MainActivity which will host the Xamarin.Forms content.

    Declarative C# as an alternative to XAML

    Declarative C# as an alternative to XAML

    Yesterday I had one of those moment where one minute you’re super opinionated on something, only for someone to point out how things have changed and that you should re-evaluate your position – As much as I have my personal preferences on a lot of developer related topics, I try to listen to those around me and look at why they’re doing things their way, and whether I can adapt/learn/extend what I’m doing.

    Yesterday in my post talking about CSS in Xamarin.Forms I made a comment that developers building for Xamarin.Forms should be using XAML and “if you’re doing it in code, you’re wasting everyone’s time”. Almost immediately after posting this I was following a related twitter thread (Adam’s thread on whether XAML is holding Xamarin.Forms back) and I saw a link to the work that Vincent has been doing on using declarative c# instead of XAML. This started with a discussion on the Xamarin forums: https://forums.xamarin.com/discussion/123771/using-declarative-style-c-instead-of-xaml-should-xamarin-redirect-xaml-efforts-elsewhere? Then Vincent provided a link to his repo on Github: https://github.com/VincentH-Net/CSharpForMarkup

    My issue with using C# to define layout is that out of the box it’s very difficult to construct layouts without it making it look like a jumbled mess – XAML makes the layout very clean and easy for any XAML developer to easily grok what’s going on. However, what Vincent has done is provide some simple extensions that make it possible to define the layout in a very fluent manner.

    Whilst I still prefer, and would recommend using XAML, if you must use C# to define layouts, you should look at the work Vincent has done and perhaps leverage it in your code. Furthermore I’d love to see some metrics on whether there is a noticeable performance gain in using C# versus compiled XAML, and how to handle styles, templates and other resources in code.

    Xamarin Forms gets CSS to pander to web developers

    Xamarin Forms gets CSS to pander to web developers

    I just finished reading a good post by fellow Microsoft MVP, Sam Basu, looking at how to use CSS for styling web development. Since becoming aware of the intent to add CSS as a styling option with Xamarin Forms I’ve been an advocate against it, not because I’m “not a web guy” but because the platform doesn’t need options. Xamarin Forms is a great platform and one that I’ve been talking, blogging and working with since it was created; it’s not perfect but it’s incredibly powerful in how quickly cross-platform applications can be generated. What it does not need is a second alternative for styling.

    In talking with the product team and other Xamarin Forms developers I’m always keen to understand their opinions, so I decided that I’d review Sam’s list of CSS benefits and try to boil them down into why I think the decision was made to add CSS. My summary of the list it comes down to (I’ve discounted the other comments because they’re just statements, not really benefits of CSS over XAML styling):

    – The developer ecosystem is inundated with web developers (ie people who know and understand CSS) so let’s give them a technology they’re familiar with (without having to learn anything new)

    – CSS is less verbose

    – CSS offers additional styling inheritance

    –  CSS can be shared between web and Xamarin Forms applications

    Let me leave the first point for a second – I promise I’ll come back to it. The second point regarding CSS being less verbose is a bit irrelevant since intellisense/autocomplete makes writing XAML styles super quick; XAML styles are then compiled and so don’t need to be parsed in the way CSS does. I have to admit, one of the only benefits I see of using CSS is around styling inheritance and referencing – this has always been a limitation of XAML styles and one that I would love to see a fix for, rather than cobbling some other styling alternative. The last point regarding sharing CSS between web and Forms might be nice in theory but as we’ve seen say across Phone, Windows, Xbox, the reality is that most of the styling needs to be adjusted per platform anyhow, so the benefits are marginal at best.

    The article goes on to talk about some caveats – I’ll rephrase this as “Here are the reasons you should never use CSS in you Xamarin Forms application”:

    – XAML styling is, and I’m guessing, will continue to be the primary way to do styling in Xamarin Forms – anything else will be built on top of this meaning that all new features will come later, if at all, to CSS

    – There are some limitations on what CSS can do, even today – do you think this will get addressed any time soon? I wouldn’t be betting the future of any project on these getting addressed in the short term, if ever.

    – CSS is parsed – Xamarin/Xamarin Forms adds enough overhead as it is, do you really want to slow down your mobile apps further. Just on this note, please make sure you optimise your apps, leveraging XAML compilation

    Ok so I mentioned I’d come back to the first benefit of using CSS which is that it’s a familiar technology for web developers – the reality is that Xamarin.Forms is for building mobile applications and unless you’ve come from a background of building SPAs with offline capabilities (such as building a PWA), chances are you’re going to need to learn a bunch more than just XAML syntax. Furthermore, if you’re going to be building with Xamarin.Forms you need to be using XAML to layout your pages (if you’re doing it in code, you’re wasting everyone’s time), so why wouldn’t you use XAML styling too.

    Now, do I think that XAML styling is perfect? – it is definitely not. The lack of even simple things like multiple inheritance, and in the case of Xamarin.Forms, basic control templates for the standard controls, are annoyances and need to be fixed. I think there is an opportunity to learn from CSS and adapt it to improve XAML across the board. Do I think this is a good enough reason for adding CSS? NO, I repeat NO – you can’t imagine the resource drain that CSS will have on the Xamarin.Forms product team (bugs, feature requests, support for new features).

    Going forward I’d like Xamarin.Forms to focus on core requirements with a view to “bringing back the magic”.

    MVX=0F: A first MvvmCross Application (MVX+1 days of MvvmCross)

    MVX=0F: A first MvvmCross Application (MVX+1 days of MvvmCross)

    Updated 16/4/2018: Reference to MvvmCross have been updated to v6.0.0

    One of the awesome things about MvvmCross is that you can take the exact same set of ViewModels that you used for your UWP, iOS, Android applications and use them in a Xamarin Forms application. As we go through the MVX+1 series, I’ll make some space for talking about Xamarin Forms as well.

    In this post we’re going to extent what we started in the previous post by adding a Xamarin Forms interface – this means creating new head projects for iOS, Android and UWP too. All up we’re adding four new projects but fear not, most of the heavy lifting is done by Visual Studio:

    Into our existing solution we’re going to add a new Xamarin Forms project:

    1. Add a new Mobile App (Xamarin.Forms) project called FirstDemo.Forms
      image_thumb1_thumb
    2. When prompted, select Blank App, make sure all three Platforms are checked and make sure you select the .NET Standard option (Do NOT use the Share Project option).
      image_thumb3_thumb
    3. Upgrade the Xamarin.Forms NuGet to latest for all four Forms projects (at time of writing is 2.5.1.444934)
    4. Add MvvmCross NuGet Package to all Forms projects (Forms, Forms.iOS, Forms.Android and Forms.UWP)
    5. Add MvvmCross.Forms NuGet Package to all Forms projects (Forms, Forms.iOS, Forms.Android and Forms.UWP)

    Note: You may need to upgrade to latest NuGet packages for all Forms projects before you can add references to the MvvmCross packages.

    Update the FirstDemo.Forms project

    1. Remove all code in App class except for constructor with a call to InitializeComponent
    2. Create Views folder
    3. Move MainPage into Views folder and rename to FirstView
    4. Adjust FirstView.xaml and FirstView.xaml.cs to change class name to FirstView and to make it inherit from MvxContentPage
    5. Add two Entry and a Label with data binding to FirstView.xaml

    Update the FirstDemo.Forms.Uwp project

    1. Update Microsoft.NETCore.UniversalWindowsPlatform (v6.0.8 at time of writing)
    2. Add reference to FirstDemo.Core
    3. Change MainPage to inherit from MvxFormsWindowsPage
    4. Remove all code other than the InitializeComponent method call in the constructor of MainPage
    5. Add ProxyMvxApplication
      public abstract class ProxyMvxApplication : MvxWindowsApplication<MvxFormsWindowsSetup<Core.App, FirstDemo.Forms.App>, Core.App, FirstDemo.Forms.App, MainPage>
    6. Change App.xaml and App.xaml.cs to inherit from ProxyMvxApplication
    7. Remove all code other than the constructor, with a single call to InitializeComponent, in App.xaml.cs

    Update the FirstDemo.Forms.Android project

    Note (1): If you run into the following error, you may need to rename your project. In this case we renamed it to Forms.Droid (as well as the folder the project resides in)
    1>C:Program Files (x86)Microsoft Visual StudioPreviewEnterpriseMSBuildXamarinAndroidXamarin.Android.Common.targets(2088,3): error MSB4018: System.IO.PathTooLongException: The specified path, file name, or both are too long. The fully qualified file name must be less than 260 characters, and the directory name must be less than 248 characters.

    Note (2): If you’re using the preview build of Visual Studio, you may run into an error: “error XA4210: You need to add a reference to Mono.Android.Export.dll when you use ExportAttribute or ExportFieldAttribute.” If you do, you just need to Add Reference to Mono.Android.Export (search in the Add Reference dialog).

    1. Change Forms.Android project to target latest Android SDK (v8.1 at time of writing)
    2. Upgrade Xamarin.Android.Support.* to latest for the Forms.Android project
    3. Add reference to FirstDemo.Core
    4. Change MainActivity inheritance, remove code except for a constructor:
      public class MainActivity : MvxFormsAppCompatActivity<MvxFormsAndroidSetup<Core.App, App>, Core.App, App>
      {
      }

    Update the FirstDemo.Forms.iOS project

    1. Add reference to FirstDemo.Core
    2. Changed inheritance of AppDelegate
      public partial class AppDelegate : MvxFormsApplicationDelegate<MvxFormsIosSetup<Core.App, FirstDemo.Forms.App>, Core.App, FirstDemo.Forms.App>

    And there you have it – you should be able to build and run all three Forms projects utilising the same view models that the non-Forms projects used

    MVX=0 : A first MvvmCross Application (MVX+1 days of MvvmCross)

    MVX=0 : A first MvvmCross Application (MVX+1 days of MvvmCross)

    [Repost: Apologies for those who have already read this but there were some issues with the link generated for the previous post, so I’ve reposted it]

    Updated 16/4/2018: Reference to MvvmCross have been updated to v6.0.0

    Yes, this is going to be a sequence of posts reworking the infamous N+1 series that Stuart Lodge did starting almost exactly 5 years ago. As we approach the 5 year anniversary of these posts I thought it only fitting to cover this series again as a way of introducing MvvmCross v6 which will be released very shortly has just been released. Unlike the original series that were YouTube videos accompanied by blog posts, this series will only contain the posts, mainly because I find generating videos to be time consuming. Anyhow, here goes:

    We’ll start by creating a Blank Solution.

    image_thumb4_thumb

    Into the solution we’ll add a Core Library that will contain an App class and our first ViewModel:

    1. Add a Class Library (.NET Standard) called FirstDemo.Core
      image_thumb3_thumb
    2. Add a reference to MvvmCross NuGet package (v6.0.0-beta.8 v6.0.0 at time of writing)
    3. Rename the default Class1.cs to App.cs, and allow Visual Studio to rename class to App
    4. Change App to inherit from MvxApplication
    5. Add a folder, ViewModels, and add a class called FirstViewModel.
    6. Change FirstViewModel to inherit from MvxViewModel
    7. Add logic to FirstViewModel to include FirstName, LastName and a calculated FullName
    8. Override Initialize method in App to call RegisterAppStart, specifying FirstViewModel as the startup ViewModel

    Let’s start with a Universal Windows Platform UI:

    1. Add a Blank App (Universal Windows) called FirstDemo.Uwp
      image_thumb6_thumb
    2. Make sure Minimum and Target versions are set to at least the Fall Creators Update so that it supports .NET Standard 2.0
      image_thumb8_thumb
    3. Update NuGet package Microsoft.NETCore.UniversalWindowsPlatform to the latest stable version (6.0.8 at time of writing)
    4. Add a reference to MvvmCross NuGet package
    5. Add reference to FirstDemo.Core project
    6. Add a help class ProxyMvxApplication to the FirstDemo.Uwp project – this is a proxy class to compensate for the lack of generics support in XAML
    7. public abstract class ProxyMvxApplication: MvxApplication<MvxWindowsSetup<Core.App>, Core.App> { }

    8. Change App.xaml and App.xaml.cs to inherit from ProxyMvxApplication
    9. Remove all code in App.xaml.cs other than the constructor which should contain a single call to InitializeComponent
    10. Delete MainPage.xaml and MainPage.xaml.cs
    11. Add a Views folder, and  add a FirstView based on the Blank XAML page template
    12. Change FirstView.xaml and FirstView.xaml.cs to inherit from MvxWindowsPage
    13. Add some TextBoxes and a TextBlock to the FirstView, complete with databinding
    14. Hit F5 and run the application (you may have to set the FirstDemo.Uwp project as the startup project and make sure it’s set to build and deploy using the Configuration Manager)

    Next let’s add the Android UI:

    1. Add a Android App (Xamarin) called FirstDemo.Droid
      image_thumb10_thumb
    2. Select the Blank App template, and the minimum Android version
    3. Update the Xamarin.Android.Support.Design NuGet package (at time of writing the latest is 27.0.2)
    4. Update the Android version to Use Latest Platform
      image_thumb12_thumb
    5. Add a reference to MvvmCross NuGet package
    6. Add a reference to MvvmCross.Droid.Support.V7.AppCompat package
    7. Add reference to FirstDemo.Core project
    8. Add a new class, MainApplication, that inherits from MvxAppCompatApplication
      public class MainApplication : MvxAppCompatApplication<MvxAppCompatSetup<App>, App>
    9. Rename MainActivity.cs to SplashScreen.cs and let Visual Studio rename the class
    10. Rename activity_main.axml to SplashScreen.axml, and adjust layout to indicate application loading
    11. Adjust SplashScreen class to inherit from MvxSplashScreenAppCompatActivity and set NoHistory to true (since we don’t want the user to be able to press the back button and go back to the splash screen)
    12. [Activity(Label = “@string/app_name”, Theme = “@style/AppTheme”, MainLauncher = true, NoHistory = true)]
      public class SplashScreen : MvxSplashScreenAppCompatActivity

    13. Add a folder, Views, and add a new Activity, FirstView.cs
      1. Add a new Android Layout to the Resources/Layout folder, FirstView.axml, with a couple of EditText and a TextView, all data bound using MvxBind
      2. You may run into an error: “error XA4210: You need to add a reference to Mono.Android.Export.dll when you use ExportAttribute or ExportFieldAttribute.” If you do, you just need to Add Reference to Mono.Android.Export (search in the Add Reference dialog).
      3. Set the startup project to be FirstDemo.Droid and press F5 to run the application

      Lastly, let’s add the iOS UI:

      1. Add an iOS App (Xamarin) called FirstDemo.iOS
        image_thumb2_thumb
      2. Select the Blank App template, Universal devices support and Minimum iOS Version of 11.2
        1. Add a reference to MvvmCross NuGet package
          1. Add reference to FirstDemo.Core project
          2. Update AppDelegate class to inherit from MvxApplicationDelegate
            public class AppDelegate : MvxApplicationDelegate<MvxIosSetup<App>, App>
          3. Add an Empty Storyboard, called Main.storyboard, to the root of the project
          4. Add a ViewController to the Main.storyboard using the designer and set the Class and Storyboard ID to FirstView (also make sure the “User Storyboard ID” checkbox is set to true)
          5. Move the generated FirstView.cs and FirstView.designer.cs files (from the previous step) into a new folder called Views, and adjust the namespace of the FirstView class to FirstView.iOS.Views
          6. Add two UITextField and a UILabel to the FirstView ViewController using the Main.storyboard designer (make sure each element has a Name set so it can be referenced from code)
          7. Update the FirstView class to inherit from MvxViewController
            [MvxFromStoryboard(“Main”)]
            public partial class FirstView : MvxViewController<FirstViewModel>
          8. Add logic to FirstView to enable databinding using the CreateBindingSet extension method
          9. Set the startup project to be FirstDemo.Droid and press F5 to run the application
            Update 16/4/2018: For some reason the iOS App (Xamarin) project template still uses a package.config. During the update to the stable v6.0.0 package the package.config file in FirstDemo.iOS was removed, the reference in FirstDemo.iOS.csproj to MvvmCross was manually removed and the following ItemGroup added:
            <ItemGroup>
               <PackageReference Include=”MvvmCross” Version=”6.0.0″ />
            </ItemGroup>

          The final code is available at https://github.com/nickrandolph/MvxPlus1DaysOfMvvmCross/tree/master/Mvx-00-FirstDemo

          To get this to work I would suggest running the latest Visual Studio for Mac or PC. Hit me up on Twitter or Slack if you have any issues following the steps or running the samples.

          Progressive Web Apps–Are these a “thing” yet?

          Progressive Web Apps–Are these a “thing” yet?

          Maximiliano Firtman has a great post that discusses the current state of play of Progressive Web Apps (aka PWAs). For me the stand outs are:

          – iOS hides the “Add to Homescreen” option within the Share extension

          – On iOS the ability to Add to homescreen isn’t available when using Edge or Chrome, despite the Share extension being a common across applications.

          – Lack of push notifications is a major annoyance from a user perspective – After installing iOS 11.3 I went and added the PWA version of Twitter (just go to https://mobile.twitter.com and add to homescreen). The app works great but the lack of any form of notifications is just crippling and means I now miss messages until I get prompted to go into the Twitter app. This alone is a reason for me to install the store version of the app.

          – PWAs still only get a limited cache, with no option to extend it with user consent, which is hardly enough to cache the static resources for a good responsive website, let alone provide offline data access

          – Windows support is still via an app coming from the store

          The upshot of this is that whilst Google is doing a great job in advocating for PWAs, the reality is that they’re still not ready for the prime time.

          Every day there are new technologies emerging; there are new frameworks available; there are new scenarios and devices to build for, so it becomes difficult as product owners, as developers, as technologists, to work out where to focus our attention. As we discussed in a recent article on App – Fomo before you jump into looking at technology it’s important to decide whether an app is even something you want to build. The true value of PWAs is that they are starting to bridge the cap between what the web can do today and the benefits offered by applications delivered by a store (eg place on the home screen, offline, push notifications). This in turn will ease make it easier to determine whether you truly need an app, or whether a modern responsive website (aka a PWA) will suffice.