I’ve been playing with Xamarin.Forms for the last few days. While it is pretty impressive that you can build an iPhone, Android and WinPhone app from the same codebase, I get a feeling that WinPhone is a second class citizen. One of the first things that bugged me is that you do not get the standard WinPhone page titles “for free”. Here is some XAML to fix that:
<!-- WinPhone page title -->
<Label Text="APPLICATION TITLE" TranslationX="4" TranslationY="4" />
<Label Text="page title" Font="64" TranslationY="-12"/>
Hopscotch is a little phone game that I started about two years ago and never got to finish. This week I started from scratch and published it in one day. The design of the game as well as the icon which I created from a screenshot turned out pretty great. And my six year old daughter absolutely loves the game, makes me feel so proud…
The Conference Call app allows you to select an invitation for a conference call from your calendar and dial into the call with one press of a button.
If you encounter an invitation that cannot be parsed properly please forward it to us and we will update the app accordingly.
Working on a new WinPhone app the other day I encountered an interesting problem which made me scratch my head quite a bit. I needed to read the list of appointments from the phone’s calendar. No big deal, right? Using the MVVM pattern I created a separate view model for my page and a service where I wanted to put all my phone specific stuff. The initial signature of my method was
public IEnumerable<Appointment> GetAppointments();
When trying to implement the method I found out that the calendar API uses the old style event based async pattern (EAP). I tried couple of different methods to wrap the async call and the result from the event in a single method call and failed miserably. After that I tried changing the method to the new async/await style. I knew I had to return a Task<T> so the signature of my method became
public Task<IEnumerable<Appointment>> GetAppointments();
But I still did not know how to make it work. And then I finally came across the TaskCompletionSource class that already solves my problem:
public Task<IEnumerable<Appointment>> GetAppointments()
return Task.Run(() =>
var tcs = new TaskCompletionSource<IEnumerable<Appointment>>();
var appts = new Appointments();
appts.SearchCompleted += (o, e) =>
appts.SearchAsync(DateTime.Today, DateTime.Today.AddDays(1), "appointments");
Beautiful, isn’t it?
In the seventies, just before I was born, Xerox (where I spent half of my career) invented MVC (model-view-controller). There are many variations of the pattern one of which is MVVM (model-view-viewmodel). While the differences between the various flavors of MVC, MVP, MVVM, etc. are in my opinion purely academic, there is absolutely no doubt in my mind that following a pattern like that can make the dev’s life a lot easier. There is somewhat of a high price for entry and a bit of a learning curve, but once you commit to it, there is no going back.
The essence of MVVM is that you separate your data (the model) from you presentation (the view) and you put all your UI logic in the view-model, where it can be developed and tested separately from the view itself. When targeting multiple platforms, in the ideal case you can reuse your models and view models across the different platforms and only code separate views.
There are several different MVVM libraries (MVVM Light, Caliburn, etc.) but it is important to understand that you do not need to bring a library in order to do MVVM, it just makes things easier. I’ve never used mvvmcross before but it promises to deliver databinding on windows, android and ios with reusable view models. It also contains a simple IoC container as well as few other tools and plugins.
mvvmcross is available as a nuget package. you add it to your projects, follow the provided (short) to-do list and you are in business. I was able to wire up a win store app with two views, view models, a service, etc. in maybe 15 or 20 minutes. Tomorrow – droids for breakfast :) …
In the recent years Microsoft, knowing that it is not quite winning the post-PC battle is trying to lure the developers to write apps for winphone/win8 by providing the best dev tools and a relatively easy path (with the partnership with xamarin) to porting apps from android or ios to winphone/win8.
So in the following days I’ll create a small demo of a LOB application on all mobile platforms using visual studio, c#, xamarin, an mvvm library, etc. My goal is to have a form and call a service with the data from the form writing as little code as reasonable and reusing it as much as possible.
The Windows 8 version of Pipes is in the store and got a 1000 downloads in the first week. Working on the first update already with a “big orange button”™ for rate and review as well as few smaller improvements.