Xamarin Forms, the MVVMLight Toolkit and I: Dependecy Injection

Xamarin Forms, the MVVMLight Toolkit and I: Dependecy Injection


Let’s just do a small recap what Dependency Injection means. The DI pattern’s main goal is to decouple objects and their dependencies. To separate concerns, we are using this structure nearly every time:

  • interface which defines the provided functionality
  • service class which provides the functionality defined in the interface
  • container that allows client classes/objects to use the functionality defined in the interface

The interface, our helpful dictator

DI always involves an interface, which dictates the functionality of the implementation. In Xamarin Forms, the interface rests inside the PCL/common project:

public interface IOsVersionService
    string GetOsVersion { get; } 

This interface gets the current installed version of the operating system. The next step ist to create the platform implementation, which is commonly defined as a service class.

Platform Implementation (service class)

We need to implement the service class for each platform. The setup is pretty easy, just add a new class and implement the interface for each platform:


Tip: I am using a separate folder for platform implementations and set it to be a namespace provider. This makes it easier to maintain and I keep the same structure in all platform projects.

Let’s have a look into the specific implementations:


public string GetOsVersion
        var versionNb = Build.VERSION.Release;
        var codename = Build.VERSION.Codename;
        return $"Android {versionNb} ({codename})";


public string GetOsVersion
            return $"iOS {UIDevice.CurrentDevice.SystemVersion} ({UIDevice.CurrentDevice.UserInterfaceIdiom})";
            return "This demo supports iOS only for the moment";


public string GetOsVersion
        var currentOS = AnalyticsInfo.VersionInfo.DeviceFamily;
        var v = ulong.Parse(AnalyticsInfo.VersionInfo.DeviceFamilyVersion);
        var v1 = (v & 0xFFFF000000000000L) >> 48;
        var v2 = (v & 0x0000FFFF00000000L) >> 32;
        var v3 = (v & 0x00000000FFFF0000L) >> 16;
        var v4 = v & 0x000000000000FFFFL;
        var versionNb = $"{v1}.{v2}.{v3}.{v4}";
        return $"{currentOS} {versionNb} ({AnalyticsInfo.DeviceForm})";

Now that we are able to fetch the OS Version, we need to make the implemation visible outside of the platform assemblies. On Android and iOS, this one is pretty straigt forward by adding this Attribute on top of the class:

[assembly: Xamarin.Forms.Dependency(typeof(OsVersionService))]

Because Universal Windows projects compile differently, we need to go a different route on Windows. To make the implementation visible, we need to explicit declare the class as an assembly to remain included first (otherwise the .NET Toolchain is likely to strip it away):

protected override void OnLaunched(LaunchActivatedEventArgs e)
    //other code for initialization, removed for readabilty
    //modified for .NET Compile
    List<Assembly> assembliesToInclude = new List<Assembly>();

    Xamarin.Forms.Forms.Init(e, assembliesToInclude); 

Now that we have our platform implementations in place, we can go ahead and use the interface to get the OS versions.

Xamarin Forms DependencyService

With the static DependencyService class, Xamarin Forms provides a static container that is able to resolve interfaces to their native platform implementations. Using it is, once again, pretty straight forward:

private string _osVersionViaDs;
public string OsVersionViaDs
    get { return _osVersionViaDs; }
    set { Set(ref _osVersionViaDs, value); }
private RelayCommand _getOSVersionViaDsCommand;
public RelayCommand GetOsVersionViaDsCommand => _getOSVersionViaDsCommand ?? (_getOSVersionViaDsCommand = new RelayCommand(() =>
    OsVersionViaDs = DependencyService.Get().GetOsVersion; 

In my sample application, I am using a button that fetches the OS version via Xamarin Forms DependencyService and display it into a label in my view.

Special case UWP, once again

To make this acutally work in an UWP application, we need to register the Service manually. Xamarin recommends to do so in the OnLaunched event, after Xamarin Forms is initialized:

//in OnLaunched event (App.xaml.cs)
//manually register for DependencyService 
//AFTER Forms is initialized but BEFORE VMLocator is initialized:

Only with that extra line of code, it will actually work like it should. If you want to know more on the fact that UWP needs a separate solution, take a look here into the Xamarin docs.

Why use the MVVMLight Toolkit’s Ioc?

There are several reasons. First is of course, purely personal: because I am used to write code for it. But there are also technical reasons:

  • support for cunstroctor injection
  • interface implementations can have parametered constructors
  • MVVMLight supports additional features like named instances and immediate creation on registration
  • in MVVM(Light) applications, you are very likely using DI on Xamarin Forms level, anyway (like in a NavigationService)

You see, there are some (in my opinion) good reasons to use the built in Ioc of the MVVMLight Toolkit.

How to use SimpleIoc and DependencyService together

If you are not relying on the DI-System of Xamarin Forms, you will have to write a lot of code yourself to get the platform implementations. That is not necessary, though. As our ViewModelLocator normally is already part of the Xamarin Forms PCL project, it has access  to the DependencyService and can be used to get the right implementation:

//this one gets the correct service implementation from platform implementation
var osService = DependencyService.Get();
// which can be used to register the service class with MVVMLight's Ioc
SimpleIoc.Default.Register<IOsVersionService>(() => osService);

This works pretty well for most implementations and provides us the possibility to use all the features MVVMLight provides. The usage then matches to what we are already familiar with:

private string _osVersionViaSimpleIoc;
public string OsVersionViaSimpleIoc
    get { return _osVersionViaSimpleIoc; }
    set { Set(ref _osVersionViaSimpleIoc, value); }
private RelayCommand _getOSVersionViaSimpleIocCommand;
public RelayCommand GetOsVersionViaSimpleIocCommand => _getOSVersionViaSimpleIocCommand ?? (_getOSVersionViaSimpleIocCommand = new RelayCommand(() =>
    OsVersionViaSimpleIoc = SimpleIoc.Default.GetInstance().GetOsVersion; 

If you do not want (or it is not possible due to complexity) register the platform implementation directly in the ViewModelLocator, you  can go down another route. You could create a new interface in the Xamarin Forms PCL which references the interface with the platform implentation as a member. Your implementation of this new interface (in Xamarin Forms) will be responsible for the getting the instance of the platform implementation via the built in DepenencyService.

I already used both ways in my recent Xamarin projects, but I prefer the first way that I described above.


Due to the fact that we know the DI pattern already as we (of course) follow the MVVM pattern in our applications, there is no big mystery about using the built in DependencyService of Xamarin Forms. We can easily integrate it into the MVVMLight Toolkit and combine the best of both worlds this way.

Nonetheless, I know that also some beginners are following my posts, so I tried to describe everything a bit more extended. As always, I hope this post is helpful for some of you. In my next post, I will show you how I solved the Navigation “problem” in my Xamarin Forms applications. In the meantime, you can already have a look at the sample code on Github.

Happy coding, everyone!

Posted by msicc in Android, Dev Stories, iOS, UWP, Xamarin, 6 comments

Xamarin Forms, the MVVMLight Toolkit and I (new series) [Updated]

Updated some code parts that needed to be changed in the ViewModelLocator.

Please see also this post for upgrading the project to .netStandard:

Xamarin Forms, the MVVMLight Toolkit and I: migrating the Forms project and MVVMLight to .NET Standard

Like some of you may have already registered, I have been doing the next step and went cross platform with my personal projects. I am primarily using Xamarin Forms, because I eventually like XAML a little too much. I took a break from round about 2 years on my Xamarin usage, and I am happy to see that it has improved a lot in the meantime. While Xamarin Forms still has room for improvementes, one can do already real and serious projects with it. As I like the lightweight MVVMLight toolkit as much as I like XAML, it was a no-brainer for me to start also my recent Xamarin projects with it.

There is quite some setup stuff to do if you want get everything working from the Xamarin Forms PCL, and this post will be the first in a series to explain the way I am currently using. Some of the things I do may be against good practice for Xamarin Forms, but sometimes one has to break out of them to write code more efficiently and also maintain it easier.

Installing MVVM Light into a Xamarin Forms PCL project

Of course, we will start with a new Xamarin Forms project. After selecting the type Cross Platform App in the New Project Dialog in Visual Studio, you’ll be presented with this screen, which was introduced in the Cycle 9 Release of Xamarin:

Select Xamarin Forms as UI Technology and PCL as Code Sharing Strategy to start the solution creation. As it creates several projects, this may take some time, so you may be able to refill your coffee cup in the meantime. Once the project is created, you’ll see 4 projects:

Before we are going to write some code, we will update and add the additional packages from within the NuGet Package Manager. If your are not targeting the Android versions 7.x , Xamarin Forms is not able to use the latest Android Support libraries, so you’ll have to stick with version 23.3.0 of them (see release notes of Xamarin Forms). Since it makes sense for a new app to target the newest Android version, we’ll be updating the Android Support packages for our sample app as well.

If the NuGet Package manager demands you to restart, you’ll better follow its advise. To verify everything is ok with the updated NuGet packages, set the Android project as Startup project and let Visual Studio compile it.

If all goes well, let’s make sure we are using the right UWP compiler version for Visual Studio 2015. The .NETCORE package for the UWP needs to be of Version 5.2.x, as 5.3 is only compatible with Visual Studio 2017.

Once the packages are up to date, we’ll finally download and install MVVMLight. As we will host all of our ViewModel Logic in Xamarin Forms, together with their Views, we just need to install it into the Portable library and into the UWP project:

There will be no changes to the project except adding the reference. We need to set up the structure ourselves. First, create two new folders, View and ViewModel:

Move the MainPage into the View Folder and adjust the Namespace accordingly. The next step is to setup a ViewModelLocator class, which takes a central part of our MVVM structure. Here is what you need for the base structure:

    public class ViewModelLocator
        private static ViewModelLocator _instance;
        public static ViewModelLocator Instance => _instance ?? (_instance = new ViewModelLocator());

        public void Initialize()
            ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);


        private static void RegisterServices()
            //topic of another blog post

        #region ViewModels  

        #region PageKeys

You may notice some things. First, I am using the singleton pattern for the ViewModelLocator to make sure I have just one instance. I had some problems with multiple instances on Android, and using a singleton class helped to fix them. The second part of the fix is to move everything that is normally in the constructor into the Initialize() method. Now let’s go ahead, add a MainViewModel to the project and to the ViewModelLocator:

        public void Initialize()
            ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);
            if (!SimpleIoc.Default.IsRegistered)

        #region ViewModels
        public MainViewModel MainVm => ServiceLocator.Current.GetInstance<MainViewModel>();

Let’s give the MainViewModel just one property which is not subject to change (at least for now):

public string HelloWorldString { get; private set; } = "Hello from Xamarin Forms with MVVM Light";

The next step is to get the App.xaml file code right, it should look like this:

<?xml version="1.0" encoding="utf-8"?>
<Application xmlns="http://xamarin.com/schemas/2014/forms" 
             xmlns:vm="clr-namespace:XfMvvmLight.ViewModel" >
    <!-- Application resource dictionary -->
    <forms:ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
      <vm:ViewModelLocator x:Key="Locator" d:IsDataSource="True" />

Now that we have set up the baisc MVVM structure, we are going to connect our MainViewModel to our MainPage. There are two ways to do so.

In Xaml:

    <Binding Path="MainVm" Source="{StaticResource Locator}" />

in Code:

        public MainPage()

            this.BindingContext = ViewModelLocator.Instance.MainVm;

After that, just use the HelloWorldString property of the MainViewModel as Text in the already existing Label:

    <Label Text="{Binding HelloWorldString}"
           HorizontalOptions="Center" />

Before we are able to test our code, we need to make sure our ViewModelLocator is initialized properly:


    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
        protected override void OnCreate(Bundle bundle)
            //TabLayoutResource = Resource.Layout.Tabbar;
            //ToolbarResource = Resource.Layout.Toolbar;


            global::Xamarin.Forms.Forms.Init(this, bundle);


            LoadApplication(new App());


    public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
        // This method is invoked when the application has loaded and is ready to run. In this 
        // method you should instantiate the window, load the UI into it and then make the window
        // visible.
        // You have 17 seconds to return from this method, or iOS will terminate your application.
        public override bool FinishedLaunching(UIApplication app, NSDictionary options)


            LoadApplication(new App());

            return base.FinishedLaunching(app, options);


//in App.xaml.cs:
        protected override void OnLaunched(LaunchActivatedEventArgs e)

            if (System.Diagnostics.Debugger.IsAttached)
                this.DebugSettings.EnableFrameRateCounter = true;

            Frame rootFrame = Window.Current.Content as Frame;

            // Do not repeat app initialization when the Window already has content,
            // just ensure that the window is active
            if (rootFrame == null)
                // Create a Frame to act as the navigation context and navigate to the first page
                rootFrame = new Frame();

                rootFrame.NavigationFailed += OnNavigationFailed;



                if (e.PreviousExecutionState == ApplicationExecutionState.Terminated)
                    //TODO: Load state from previously suspended application

                // Place the frame in the current Window
                Window.Current.Content = rootFrame;

            if (rootFrame.Content == null)
                // When the navigation stack isn't restored navigate to the first page,
                // configuring the new page by passing required information as a navigation
                // parameter
                rootFrame.Navigate(typeof(MainPage), e.Arguments);
            // Ensure the current window is active

Let’s test our app on all platforms by building and deploying them:


iOS Screenshot – post will be updated 


If you get the same screens, you are all set up to use Xamarin Forms with MVVMLight.


I know there are several specialized MVVM frameworks/toolkits floating around, which are commonly used for Xamarin Forms. As I am quite used to the MVVMLight toolkit, I prefer it over them. It is a lightweight solution, and I have more control over the code that is running than with the other options. I know I have to handle a lot of things in this case on my own (Navigation for example), but these will get their own blog posts. Starting with one of the future posts in this series, I will provide a sample app on my Github account.

If you have feedback or questions, feel free to get in contact with me via comments or on my social accounts. Otherwise, I hope this post and the following ones are helpful for some of you.

Happy coding, everyone!

Posted by msicc in Android, Dev Stories, iOS, Xamarin, 12 comments

Review of a geek’s 2014

We are close to the end of this year 2014, time for a little review.

At the beginning of the year, I was mostly busy with working on my UserVoice library that makes it easier for me and other developers to integrate UserVoice into Windows Phone apps. I also launched Voices Admin, the companion app for the library. I will start to rewrite this library in 2015 to make it a true Universal library for Windows, Windows Phone as well as Xamarin (and make it return objects instead of naked JSON strings).

I also had some troubles with my former hoster, which lead to a total domain chaos and finally ended in January, too. Thanks to Azure Websites, the transition should have been without problems.  At Telefónica, I was busy finishing the internal App “Friends & You” for Android and Windows Phone. I learned a lot using Xamarin for the Android version, and even more about corporate rules and requirements. In the beginning of December, I also finished the iOS variant of the app (using Xamarin.Forms) – which is sadly set to be not launched for the moment (mostly because of my departing of Telefónica).

During the year, we also received the Windows Phone 8.1 Developer Preview. It removed the ability to cross post on social networks on Windows Phone. As this was one of my most used features, I decided to solve this problem for myself and started to write my own cross posting solution. As some of my followers recognized this, I continued my efforts to a more public and polished version, the result is UniShare for Windows Phone.


Since the first WP8.1 Developer Preview, we also have Cortana. Cortana is an awesome piece of software – if you are willing to use your phone with English and US region settings. I tried the UK version as well as the Italian and German version, but was only satisfied with the US one. I truly hope that the other countries will be on par in 2015.

I also updated my very first app ever (Fishing Knots +) to a Windows Phone 8 only version, leaving the old version for WP7 users. Also my NFC Toolkit received some love (and will receive even more in 2015). On top, I started to work on a Universal library for WordPress, which I will also continue to work on in 2015 to make it even better.

One of my saddest geek moments was when the screen of my Intel developer Ultrabook broke shorty before Christmas. As I need to be able working while on the go, I needed a replacement. I found it in the ASUS TP300L Transformer Flipbook, which is an awesome piece of an Ultrabook. On top, Santa (aka my wife) gifted me an HP Stream 7 tablet, that perfectly fits my needs for a tablet use (reading, surfing, playing some games). And so this part also turned well.

The most significant thing happened in September, when I read about a job as a C# Junior developer in Switzerland. I am truly happy about the fact I got this job (read more on it here), and already learned some new things in WPF. Currently, I am also working on my first WPF application, that is a practicing project for my new job I am going to start next year. Which leads me to the end of this short review.

2014 was a year with ups and downs like every year. I had some trouble in “first world” that we were able to solve as family (and friends), but made some good success in my geek and dev world. I am looking forward to 2015, where I am starting a new chapter in my dev story (with becoming a full time developer). But there are also some nice side projects, like maybe porting some apps to Android as well as the Internet of Things, which I am looking forward to dive in deeper. And of course, like any other MS fan, I am looking forward to the next evolutions of Windows 10!

What are you all looking for? How was your 2014? Feel free to comment below.


Happy New Year, everyone!

Posted by msicc in Editorials, 1 comment

Goodbye Telefónica (Germany), Hello ShareCommService (Switzerland)

Yes, you read that right. Today was my last work day at Telefónica, where I worked since June 2007. During that time, I learned a lot about how good customer service should be, and even more about mobile networks and mobile devices (phones, tablets and more). During that time, I also started my dev story in my spare time – all because there was not a single fishing knots application available for Windows Phone (read more here).

This lead to get recognized also within Telefónica as a developer, and so I was asked to concept and develop the application Friends & You (nope, you can’t download it as it is an internal app).  I learned a lot about how corporate apps aren’t that easy to concept and build during that time, as well as as how restrictive corporate rules can be. After all, I had a few challenges to complete. Thanks to Friends & You, I was also able to dive into the world of Xamarin, where I learned a lot about the application structures of Android and iOS (which will be helpful for eventually porting some of my Windows Phone apps to those two).

I want to say thanks to my colleagues, you´re awesome! Keep up the great work you´re doing in Customer Service.

Back in September then, I opened up my Twitter app and the first tweet I read was this one:


I opened the attached document and read the job description. As an self-thought developer, I first was about to close it and put it aside as “read and done”.

Due to the head count freeze at Telefónica after acquiring e-Plus from KPN, there are no chances to become a real full time developer within Telefónica for the next time. But that is what I want to do. After reopening the document and reading it again, I decided to get in contact with Roman Mueller (who I knew from Twitter already).

We talked about the job itself and the circumstances behind the announcement. After a few talks and a visit in Switzerland, the decision was made. I am starting the next chapter of my developer story in January, moving to Switzerland, where I will add deeper SQL knowledge, WPF and a lot more to my development knowledge.

At this point, I want to thank ShareCommService and especially Roman for all the help I received already to make this all happen and get started.

It is going to be an exciting journey for me (and my family), and we are ready to go.

Happy coding everyone!

Posted by msicc in Dev Stories, Editorials, 1 comment

My experiences with Xamarin.Forms


As I have finished my first iOS app with Xamarin.Forms, I want to share my experience that I made during writing it.

It sounds great. Build the code once, run it on Android, iOS and Windows Phone (8). Xamarin is using the well known PCL to achieve this goal, or a shared asset project.

As I am familiar with the PCL structure, I decided to go with this one. The application I wrote for Telefónica had already their Windows Phone and Android counterpart. My thought was to bring together all three after finishing the iOS app into the Xamarin.Forms project to make it easier to maintain them (that was before it was clear that I would leave, but that’s another story). In the end, I focused on the iOS platform and implementation, leaving the other two out.

It was far easier to start a new iOS app with Xamarin.Forms than in the traditional way. Although there are some XAML gotchas (like Nicolò wrote already on his blog), it is pretty easy to get started with it.

The number one tip I can give you is to wrap everything in a principal Grid and set you ColumnWidth (also if you have only one single Column). This will help you to better position your controls on the page.

One really annoying thing is the missing IntelliSense support when you’re writing your XAML code. What does that mean? It means your will spend a lot of time with trial and error as well as reading the documentation in the beginning.

One thing that is solved in a good way is the access to native functions that are not implemented in the Forms project. Connecting through interfaces and Xamarin’s DependencyService, you can write the implementation you need in the native project and call the function from the Forms PCL. I will cover this in another blog post.

Often, you want/need your app to be designed in a different way (like I had to for Telefónica). Some basic modifications are possible from the XAML part. But the most effective way to achieve this goal for the whole app is to use Custom Renderer. This will be another post’s topic in the coming days.

Overall, Xamarin.Forms is already impressive. But you need to know that you will work with some workarounds when you start. If you are willing to do this, you might be able write a cross platform app in little time.

If you do not want to dig into the documentation or use the techniques I wrote about, Xamarin.Forms might not yet be your starting point for your cross platform app.

One last tip: To make it easier for you, there is the Xamarin.Forms Lab project. This community project has already extended Xamarin.Forms, and is worth a look and a second thought if you truly want to do a cross platform app with Xamarin.

Happy coding, everyone!

Posted by msicc in Dev Stories, Xamarin, 2 comments

WordPressUniversal – a PCL library for WordPress based C# mobile apps


As I have already developed a news reader app for my blog, I got asked quite a few times if I want to share my code to help others creating their apps. As I need to redesign my blog reader to match the latest OS features of Windows and Windows Phone, I decided to create my WordPressUniversal library.

Automattic, the company behind WordPress, integrated a powerful JSON API into their JetPack plugin. My library is based on this API. Please make sure the JSON API is active on the blog you are developing your app for.

The library currently provides the following features:

  • getting a list posts or pages
  • getting a list of all categories
  • getting a list of comments for the site and single posts
  • supports Windows Phone 8 & 8.1 Silverlight, Windows Phone 8.1 RT, Windows 8, Xamarin.iOS and Xamarin.Android

The library deserializes all data into C# objects you can immediately work with.

It is still a work in progress, but as it provides already a bunch of options to get you started, I am making this public already.

I am constantly working on the library, so be sure to follow the project along.

Note: JetPack’s JSON API does not support guest commenting at the moment. I already reached out to Automattic to (hopefully) find a solution for this. If you cannot wait, Disqus has a portable solution for Windows Phone apps.

Please make sure to see the documentation on my GitHub page.

If you have any questions, idea, wishes for me, just post a comment here or ping on Twitter.

Happy coding everyone!

Posted by msicc in Archive, 17 comments

Book review: iOS Development with Xamarin Cookbook (Dimitris Tavlikos)

I love to learn and expand my knowledge. Because of this, I was absolutely happy when I was asked for a book review about Dimitris’ iOS book.

The book is a huge collection of iOS recipes using Xamarin. The first three chapters are going deeply into the UI of an iOS application, looking on a lot (almost all) possible aspects of UI elements. What I like very much is that the author shows the code, usually with a step by step guide, and after that delivers a detailed explanation why something works in the way it does.

The next two chapters are all about creating and displaying data, files and sqlite, providing the same experience as the first chapters.

The sixth chapter is all about consuming services, such as web services, REST services or even WCF services (I wasn’t even aware of this being possible). Very good starting point for so many app ideas.

So far, the book shows already a lot of what we can do with Xamarin. But modern apps often contain media content: videos, photos, capturing media – this is what chapter 7 is all about.

Like all modern Smartphone operating systems, iOS provides some methods to let our apps interact with the OS. The 8th chapter is all about those interactions, like contacts, mail and more and has the matching real world scenarios.

The most usable apps use a device’s sensors, touch and gestures. Of course, with Apple being the leader in this space for a long time (we just need to be fair in this point), iOS has a lot of APIs for these. Chapter nine has some good recipes to help us with improving our app’s UX.

If your app needs location services and maps, chapter 10 is your friend. It shows you how to interact with Apple’s map services, add annotations and a lot more.

Users love when apps have some nice animations when something changes in an app. iOS provides a lot of options, and chapter 11 explains a lot about animations and drawing methods.

One of the most important parts when developing an app is lifecycle handling. As with any other OS, also iOS has its specific methods to handle the lifecycle. Background operations are part of this handling. In chapter 12, Dimitri tells us a lot about handling the states of an app as well as background operations.

Chapter 13 consists of tips and recipes for localization of an iOS app.

One of the most important steps when creating an iOS app is deploying the app. Apps should of course be tested on real devices, and this what chapter 14 is about – but not only. Also the required steps to prepare and app for submission as well as the submission to the store are explained.

The final chapter contains some additional recipes that can make your app more valuable like content sharing or text-to-speech.


I only began with Xamarin.iOS a few month ago. This book provides a great insight into development for iOS using the Xamarin IDE. As I said already, I like the approach of showing code first and then explaining what it does exactly and provide additional info if suitable. This book is absolutely worth every single cent if you want to start with iOS and Xamarin.

If you’re interested in the book, you’re just a click away: http://bit.ly/1tnxmGX

Note: This post was completely written on my phone. If you find typos, you can keep them ;-).

Posted by msicc in Dev Stories, iOS, Xamarin, 0 comments

Xamarin: Android Activities, Context, Intents and Views


If you are coming from C#/Silverlight, Android can be a little diffusing. Android does not have the same structure than a Windows or Windows Phone app.


Android has Activities. Activities are the key classes of Android were all actions take place. Unlike other apps or programs, you do not have a “Main” program that is your starting point when launched.

In Android, the starting point is an Activity. The Activity needs to be declared as the starting point. When you start a new project in Xamarin, an Activity called “MainActivity” gets created automatically.

This Activity has some attributes:

[Activity (Label = "gettingstarted", MainLauncher = true)]

The ‘Label’ attribute is what you will see in the Title bar when launching the app. The attribute ‘MainLauncher=true’ tells the application to start from here. Think of this as your MainPage.xaml.cs in a Windows Phone app.

Every Activity has its own OnCreate event, where you can put all your starting, button handlers, stylings etc. in.

But an Activity still has more. It has events like OnStart(), OnPause(), OnRresume() and OnStop() and OnDestroy() and OnRestart(). I won’t get into deep this time, as the Xamarin documentation has already a very good overview of those events: http://docs.xamarin.com/guides/android/application_fundamentals/activity_lifecycle/.

Those events are important to understand for a lot of your application logic, like:

  • saving data that has to be persistent
  • starting and pausing animations
  • register and unregister external events
  • fetch data that are passed from other Activities
  • and more (we will cover some of them in my further posts)

I absolutely recommend to go to the link above to read and understand those events.


The Context is often needed in an Android application and allows your code to be run within an Activity.

The Context allows you for example:

  • to access Android services,
  • to access Application resources like images or styles,
  • to create views
  • to assign gestures to an Activity

Without Context, often code does not get accepted by the IDE or makes your code getting ignored while running the app. Luckily, all methods that I used so far have been telling me if they want a Context, so you need only learn to find out if you need Context for the Activity resources or Application resources.


But what if we want to have another page (like a separate about page for example)? How can we navigate between pages or call external functions?

This is what Intents are for. Intents are sending messages through the application if another function needs to be started, like the launch of a second page. Within these intents, we have declare the actions that the app needs to do, and if we need a callback, this will also be passed with an Intent.

Let’s hold this high level, here are some lines of code that navigate to a second page (Activity):

var second = new Intent(this, typeof(SecondActivity)); StartActivity(second);

With this code, we are creating an new Intent with Context to our current running Activity to launch the SecondActivity.

To send data between Activities, we use the PutExtra() method of Intents:

var second = new Intent(this, typeof(SecondActivity)); 

second.PutExtra("FirstPage", "Data from First Page"); 


Of course, we need also some code to read the passed data on our second page:

Intent.GetStringExtra("FirstPage") ?? “Data not available”;

We could now use this data on our second page by assigning it to a control or function.

Passing data between activities works similar to passing QueryStrings in NavigationsService.Navigate() method on WindowsPhone, so you should get familiar with it very fast.


The last part that is very important are Views. In a View you declare how the Activity looks like. Think of it as your MainPage.xaml page in a Windows Phone app.

Views can be very different, too. Let’s start with the simple View. In our getting started project, we also have a Layout file that holds our first View:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:text="@string/hello" />

The View has a main LinearLayout which is acts as  ContentPanel. All other controls like Buttons, TextViews etc. are going into this. There are a lot of properties that can be set, we’ll leave it this easy for now. If you want to know more about those properties, you can have a look at the Android documentation here: http://developer.android.com/guide/topics/ui/declaring-layout.html

This part is totally the same as with the one matching part in the Android SDK, so you will need to get familiar with the Android documentation as well.

To make a View visible, we need to assign it to an Activity. In our sample app, we are doing this with this line of code in our OnCreate event:

SetContentView (Resource.Layout.Main);

This is the easy way for Views. But there are more complex Views in Android, too.

Views are also used in ListViews, where you declare the look of the items and the list in a Layout file, or also if you use the ActionBar with a tab navigation, and also in the menu of an ActionBar. I will cover all of these in my further blog posts, as we also need Adapters to get data binded to Views.

I hope you this post helps you to understand  the high level structure of an Android application.

Until the next time, happy coding!

Posted by msicc in Android, Dev Stories, Xamarin, 0 comments

A year in the like of MSicc – my review of 2013

dev smurf

2013 was a year with a lot of surprises. It was a year full of community work for me as well as a huge learning year in development. But my year had also dark clouds on heaven. This post is my personal review of 2013 – you can like my impressions or not.

I started the year with releasing my first Windows 8 app ever, along with an huge update to my blog reader app for Windows Phone. I wrote several blog posts and started also development of my NFC Toolkit app for Windows Phone (Archive: January). I also ran a beta test for my NFC Toolkit, and finished my series about the parts that should help other developers  to write a blog reader app for both Windows and Windows Phone (Archive February & Archive March).

Then in April, the first time I had dark clouds hanging deeply in my life, affecting all parts – family, community work and also my 9to5 job. My wife had once again problems with her back, caused by slipped discs. It went as far as she needed to rest in hospital for a pain therapy. Luckily this therapy was helping her and our life went back to normality (knocking on wood).

I also started a new series on the WinPhanDev blog – Why we started developing (WWSDEV). We are collecting stories from developers, and posting them over there to motivate other developers and keep the community spirit alive. Just have a look, we have really great stories over there.

In the last days of April/beginning of May, Iljia engaged me to start using Windows Azure Mobile Services to make an app idea reality: TweeCoMinder was born. It is a very special and unique app, interesting for those that don’t want to miss their special counts on Twitter, supported by real push notifications via WAMS for both Live Tiles and Toast Notifications. I learned a lot during setting up my WAMS for the app, and I did also write some blog posts about that (AzureDev posts).

Because of TweeCoMinder, I stopped developing my NFC app for that time, and did only bug fixing updates to my other apps.

In August (at least in the spare time I had), I moved my blog completely to run in a Windows Azure VM. I did it to get more control over the whole system and to learn more about running a web service. I still need to write my blog posts about setting the VM with LAMP on Azure, but I just didn’t have time for that until now. In August/September I also had again very very dark clouds hanging around, with my wife was very ill (you can’t even imagine how happy I am about the fact she has this part behind her). But our daily live is still affected by this – we just learned to arrange us with the new situation.

In October, I got back to my NFC Toolkit to finish it finally. The app has some cool and unique features utilizing NFC tags, and I am quite satisfied with my download numbers. NFC Toolkit is my main project for the moment.

But also on my 9to5 job I came to write code. I was asked to write an internal app for Windows Phone (Telefónica has a partnership with Microsoft, and so the company is flooded with Windows Phones). I used this to learn more about speech recognition on Windows Phone, as this is part of the application (Make your app listening to the user’s voice).

And finally, I also started with my very first Android app using Xamarin while porting the Windows Phone app I wrote before. I recently started to blog about my experiences with Xamarin (read more here).

In between all those projects, I made a basic reader app for the fan blog “This is Nokia”, using a PCL project for both Windows Phone 8 and Windows 8. I also wrote a simple car dashboard app to integrate it in my NFC Toolkit app as well as Mix, Play & Share, which was written on a lonely Saturday night while my kids where sleeping an my wife was at her best friend.

Through the year, I learned a lot of coding, but also a lot about people. I made some very positive experiences – but also bad ones. I am always willing to help (if my still growing knowledge enables me to do so) – but sharing a feature rich app to another person isn’t helping – if you want to learn about development, there are plenty ways to do so. We have really great developers that blog about their experiences in our community, and by understanding how to code, you truly learn. Just using an already working app and restyling it, is the wrong way.

Well, that is what my year was about – a lot of coding, learning and again coding.

Dear followers, friends, WinPhans & WinPhanDevs – thank you for being with me this year. Let’s make 2014 an even more exciting year.

I wish you all “a good slide into the new year”, as we say here in Germany. May god bless you and your families also in the new year.

Posted by msicc in Editorials, 0 comments

Xamarin: Resources of an Android app project

As I mentioned already in my first blog post about Xamarin, Android has a different project structure – even if you use Xamarin.

A very important part of this structure are resources. We have different kind of resources in an Android app:

  • Icons & Images
  • Layout (XML files)
  • Values (string resource files)

Let’s start with Icons & Images.

As you can see in the solution window, there is a folder called ‘Resources’. Here you will put all kind of resources, like images, icons, layouts and so on.

The corresponding class for images in Android is called ‘drawable’, that holds a reference to’ Icon.png’. The project structure is based on that, that’s why the resources folder has all images inside the folder ‘drawable’. As Android has various screen sizes, you may have a folder for structure like ‘drawable’, ‘drawable-hdpi, ‘drawable-ldpi’ and so on. Android scales your image resources to match the screen automatically if you do not define alternate layouts.

To make your files available in your app, you need to set the Build Action to ‘Android Resource’:

Screenshot (278)

Let’s have a look to the Layout files:

Layout files are XML files that contain the UI of a page, control or a view. You can use these XML files for example to define items of a ListView or simply the application page. Every new project has a ‘Main.axml’ file.

There are two ways to create a layout. The first one is using the visual designer:

Screenshot (280)

This works for basic layouts like adding the button above. Also, if you don’t know the properties of a control you added, you will be able to add it here to get started.

If you are familiar with writing your UI in code (like XAML)  and want to do so in your Android app, just click the ‘Source’ tab at the bottom in the visual designer. You will see something like this:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:text="@string/hello" />

If you want to add and modify a control, but don’t know how the properties are, this page has a list of all controls, which are called ‘widgets’ in Android. That’s also the corresponding namespace: android.widget.

Like in an Windows Phone app, you also have a string resource file in Android projects. This file is once again a XML file, but with a different structure:

<?xml version="1.0" encoding="utf-8"?>
<string name="hello">Hello World, Click Me!</string>
<string name="app_name">gettingstarted</string>

All strings need to be declared inside the <resources> tag. The definition is always like <string name=”yourstringname”>stringcontent</string>. Empty strings are not supported and will throw an error at building your project.

Let’s have a look on how we can work with our resources, based on our gettingstarted project. We have the following code inside our MainActivity class:

int count = 1;

		protected override void OnCreate (Bundle bundle)
			base.OnCreate (bundle);

			// Set our view from the "main" layout resource
			SetContentView (Resource.Layout.Main);

			// Get our button from the layout resource,
			// and attach an event to it
			Button button = FindViewById<Button> (Resource.Id.myButton);
			button.Text = GetString (Resource.String.hello);

			button.Click += delegate {
				button.Text = string.Format ("{0} clicks!", count++);

As you can see, the we are defining our view from our Layout file ‘Main.axml’ by using the SetContentView() method. The file is added to our resources list as Layout with the name we defined.

Our MainActivity does not know that we have a button inside our layout. To make the button visible to our MainActivity, we need to reference it. This is done by declaring a Button instance and using the FindViewById<T>(ResourceName) method.

If you have not given your button a name, now is the right time to do so. In our example the button has the name “myButton”.  The syntax is very important, make sure you add “@+id/” to the name.


Now our button is visible to our MainActivity code page and can be accessed. The sample project references the button content in the Layout file:


After referencing our button, we could also use the following code to get the button content from the resource file:

button.Text = GetString (Resource.String.hello);

Whenever your want to get a string from the resource file in an Activity, the GetString() method is used.

I hope this post helps you to understand how resources are used in an Android app and how to handle it a Xamarin project.

Happy coding everyone!

Posted by msicc in Android, Dev Stories, Xamarin, 0 comments