Category Archives: Mobile Development

Xamarin – User interaction with image views

It’s sometimes the simplest of things I tend to overlook when debugging.

While recently working on one of my company’s mobile apps, I came across an issue which had me stomped for a good 30 minutes before realizing how easy it was to resolve.

Part of the work involved creating custom views in our app to display mobile ads.  UIImageViews to be exact.  This view contains a full screen image, and a close button at the top right of the view to dismiss the ad.  Simple, right!  Well, the problem was no matter what I did, the close button did not respond to any touch events.

As you can see from the code sample below we’ve taken the route of using C# to create some of our views.  Here is what the constructor of the subclassed UIImageView looked like before solving the problem.

public FullPageAdView(float adWidth, float adHeight, Ads ads) : base(new RectangleF(0, 0, adWidth, adHeight))
if (ads == null)
throw new ArgumentException("Mobile Ads are missing");

MobileAds = ads;
closeButton = UIButton.FromType(UIButtonType.Custom);
closeButton.SetImage(UIImage.FromBundle(“RedCloseButton.png”), UIControlState.Normal);
closeButton.SetImage(UIImage.FromBundle(“RedCloseButtonClicked.png”), UIControlState.Selected);
closeButton.TouchUpInside += OnCloseButtonClicked;


We’ve properly registered the TouchUpInside button event and added the button to our custom view.  Should just work right…NOPE!  Turns out many of the controls in UIKit, including UIImageView, do not have touch enabled by default.  It has to be turned on as you can see in the snippet below.

public FullPageAdView(float adWidth, float adHeight, Ads ads) : base(new RectangleF(0, 0, adWidth, adHeight))
if (ads == null)
throw new ArgumentException("Mobile Ads are missing");

MobileAds = ads;
closeButton = UIButton.FromType(UIButtonType.Custom);
closeButton.SetImage(UIImage.FromBundle(“RedCloseButton.png”), UIControlState.Normal);
closeButton.SetImage(UIImage.FromBundle(“RedCloseButtonClicked.png”), UIControlState.Selected);
closeButton.TouchUpInside += OnCloseButtonClicked;
this.UserInteractionEnabled = true;

If you are using Xcode to create your image view, here is what the option looks like (borrowed image from here).


And there you have it. Simple solution to a simple problem.

I hope this saves someone else the hassle and time I spent in resolving this issue.

Happy Xamarin trails!

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Xamarin App Rejected – Position Independent Executable

Recently, my Xamarin mobile app was rejected from the App store with the following error.

Non-PIE Binary – The executable ‘’ is not a Position Independent Executable. Please ensure that your build settings are configured to create PIE executables.

Turns out Apple recently introduced an extra step in the build process , which now requires your app to be built as Position Independent Executable (PIE).  Position Independent Executable (PIE) applications can be loaded at a random memory address when run. This has security benefits for your application. iOS 4.3 or later, and OS X 10.7 or later, fully support PIE executables.

Fortunately, Xamarin has also updated their framework to support building applications as PIE.  You can find this update via the Beta Channel, Xamarin iOS 6.3.7 to be exact.  So any native executable is now built as PIE by default.

I hope anyone who runs into the PIE issue finds this helpful.

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WinRT: FrameState _PageKey Error

While working on my latest Windows store app, I ran across an issue while performing some navigation between pages.  See the error screenshot below.


You need to make sure that the page being navigated to is calling base.OnNavigatedTo in their OnNavigatedTo methods.  This is because that is where the page key is set up, which is required for when you’re navigating away from a page to save its state.


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WinRT: Unable to activate windows store app

I recently came across this error while building my latest Windows Store app, and found it to be extremely frustrating to say the least.  So I thought I’ll post what I did to resolve it.


After several attempts to resolve the problem, some of which included acquiring a new developer license (via the Project -> Store menu in Visual Studio), restarting Visual Studio, and even restarting the machine.  All to no avail.

Finally, I decided to “pretend” I had just created this project, so I went to the BIN and OBJ folders of the project and deleted EVERYTHING under those folders.  And BINGO, it started working again.

I’m sure some folks have already come across this and have been able to resolve it, but I hope this helps the folks who might just be starting out with Windows 8 development

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Cross-Platform Mobile Development

With a plethora of options for building mobile apps, be it a “build for each platform”, or “build once for all platform” strategy, there is a lot of argument around what path is the better one. The main points discussed are whether the Native or Hybrid approach is more appropriate. My response to a lot of these discussions has and, I think, always will be IT DEPENDS.

Going Native – Programming in the native language of the platform, I think, will always be the preference. Especially for applications that require the innermost workings of the platform. Apple iOS has Objective-C, Android has Java, and Windows Phone has .NET. Well, I guess we can’t forget about the Blackberry platform which primarily is built using Java.

Going Cross-Platform (Hybrid) – Today, there are more hybrid solutions to mobile development than one can keep up with. I liken the hybrid route to traveling to a foreign country, say France, where French is the primary language (like…obvious), but since I don’t speak the language fluently, I use a mixture of English, and hand gestures. It works, and will probably help me communicate decently, but it only goes so far, and can only accomplish so much. At some point, I’ll need to speak French. Some big players in this field include Sencha, Phonegap, & JQuery Mobile, just to name a few. I have personally played around with Sencha the most, and while it is an incredible platform, I found it to have somewhat of a steep learning curve, but that’s just me. Again, I just don’t speak “French” that well.

However, imagine if you had a French translator. Someone who can bridge that gap between you, and the oh so lovely French folks, without any loss in the quality of the communication. In fact, this translator not only spoke French, but could speak about every other language known to man, well, maybe except one (*cough* Blackberry *cough*). You could effectively use your translator anywhere in the world.

In the hybrid/cross-platform mobile development realm, I consider this “translator” to be Xamarin.  As it says on their website,

Xamarin is unique in this space by offering a single language – C#, class library, and runtime that works across all three mobile platforms of iOS, Android, and Windows Phone (Windows Phone’s indigenous language is already C#), while still compiling native (non-interpreted) applications that are performant enough even for demanding games.

It is a very powerful platform to say the least.  A game changer if you ask me.  Xamarin not only combines the powerful of all 3 platforms, but it adds its own features on top.  Some of which include:

Bindings for the Indigenous SDK: Xamarin provides strongly-typed binding for nearly the whole underlying platform SDKs in both iOS and Android.  Some advantages to this include type checking during development, and compilation.

Invoking native libraries – This gives you the power to use existing iOS and Android libraries written in Objective-C, Java or C/C++.  Xamarin just released a tool, Objective Sharpie, which takes much of the manual work of translating Objective C APIs into binding definitions that are consumed by Xamarin’s binding tools.

Modern Language features – Xamarin applications are written in C#, allowing developers to take advantage of strengths such as Dynamic Language features, and Functional Constructs such as LINQ, Lambdas, Generics, etc.  Many of these features are significant improvements over Objective-C and Java.

Use of Base Class Library (BCL) – Xamarin utilizes the .NET BCL, which is a collection of many classes that provide a comprehensive set of features like XML, Database, Serialization, Networking, and IO support, to name a few.

Amazing Development Environment – Formerly called MonoDevelop, Xamarin has revolutionized their Integrated Development Environment (IDE), now called Xamarin Studio.  It also provides deep integration with the Visual Studio IDE, allowing the .NET developer’s favorite IDE to be used for development as well.

Mobile Cross-platform support – With the support coverage across all three platforms (iOS, Android, Windows Phone) provided by Xamarin, developers can expect to share up to 90% of their code.  During my last project, we estimated a code sharing rate of about 80%, saving a ton of time and effort in development and time to market.  We were able to release two apps for both the iPhone and iPad, in 100 days (from Concept to Store).

Over the next few weeks/months, I’ll be sharing many of my experiences using this incredible framework, and engage with the dev community, while learning from you all as well.

Happy Xamarin trails!

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Update Xamarin assemblies in 3rd party dll’s

Since the birth of Xamarin.iOS 6.0 (formerly MonoTouch), many of the platform assemblies are now been signed. Some of which include the monotouch.dll, MonoTouch.Dialog-1.dll and OpenTK-1.0.dll.

In many of our projects, we use 3rd party dlls that have a reference to these now signed Xamarin assemblies.  When you upgrade to Xamarin.iOS 6.0, it causes annoying assembly version build errors.  So what can one do?  Wait for the 3rd party vendors to update their assemblies?  I think not.

In comes the Xamarin.iOS reference updater.  Thanks to Rolf Bjarne Kvinge, a Xamarin-ian no less, you won’t have to wait on those pesky 3rd party vendors to update their Xamarin assembly references.  The reference updater project provides a simple Xamarin solution, which you open and build using Xamarin Studio.  After building the solution, you will need to open a terminal window, navigate to the project directory where iOSRefUpdater.exe is located and execute the following command to convert the third-party assembly in place.

mono iOSRefUpdater.exe /path/to/third/party/assembly.dll

One other nice feature of this utility is that it also creates a backup of the assembly being converted in-place.

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Congress Watch for Windows 8

Last year, as I set out to explore the Windows Store app dev ecosystem, I pondered what my first project would be.  On the Windows Phone platform, my first app was a diary app called Easy Diary, which has done very well (but is in need for some Windows Phone 8 upgrade magic).  It was also a few months before the Presidential elections, so I figured, why not create something that would help folks like you and I keep tabs on what is going on in Washington.  So Congress Watch was born.


Congress Watch is a gateway to detailed information about your elected U.S. Congressional officials. A great way to learn about those who represent you in Congress.
With profile details, news feeds, and videos, become an informed and active citizen between elections and different sessions of Congress.


Basic Information
List of all legislators, including member first and last name, title, and political party affiliation.

Contact Information
Official website link, member contact form, Washington, DC office address, telephone, and fax numbers.

Legislative activity
Included are up-to-date news, and YouTube videos for Congress members. 

Bonus Features
Live tiles for congress members which display current news and allow users to launch directly to the legislator profile page within the app. Search for legislators, and Share with your family and friends.

This app was built using the Open Congress and Sunlight Labs API’s, but is currently not endorsed by either party.


So if you are at all interested in finding out what our folks up in Congress are doing (or not doing), then please check out my app.  Click the image below to download Congress Watch from the Windows Store.

P.S. Version 2 is already in the works and promises to deliver an improved user experience and a more organized wealth of information (along with a few premium features).  Any suggestions/ideas are most welcome.

Congress Watch Promotional

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Job Compass for Windows Phone 7

Need an app to help you make that next career decision?  Look no further than Job Compass, a decision-making app to aid you in your next career move.

Job Compass is powered by extensive data from CareerBuilder, Zillow©, and the U.S. Department of Labor, and is currently only available on *Mango* phones.

Here’s what Job Compass does for you:

  • Allows you to search for jobs provided by CareerBuilder (Quick and Advanced options)
    • Multiple search criteria including location, company name, pay, industry, employment type, etc.
    • Easy browsing for large result sets
    • List & Map views of jobs
    • Sort and filter your search results
    • Save search criteria for future viewing
  • Job details
    • Includes infsuch as job title, description, requirements, company contact info, etc.
    • Save jobs as favorites for offline viewing
    • Map of job location with turn-by-turn directions (where available)
    • Neighborhood infbased on job location (Homes for sale, etc.). Powered by Zillow©
    • Visualized career stats in job-related fields (Yearly/Hourly wages & Employment #’s)
    • Share via Email, Twitter, Facebook, etc.
    • Apply for job via Careerbuilder website
    • Live Tiles (Pin job tiles tyour phone)
  • Explore Job/Career Trends
    • Occupations with highest employment
    • Top wage earning occupations (Yearly/Hourly)
    • Visual charts texplore trends
  • Explore recent Job/Career stats
    • Yearly/Hourly Wage Percentile breakdowns
    • Visualized career stats
And of course, can’t forget some screenshots and video.

So go grab your copy of Job Compass.
P.S. Job Compass is participating in the Occupational Employment Stats Challenge.  This is a development competition hosted by the Department of Labor.  I would love if you could show your support by casting a vote for my app.  Thank you so much.  Please see the link below.
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Amber Central for the Windows Phone 7

Amber Central for the Windows Phone 7 (a free app) is designed to help in the search for, and safe recovery of missing children.

It includes:

  • A real-time feed of active AMBER Alerts from the National Center for Missing & Exploited Children® (NCMEC) including some information about the victim, when and where they were reported missing, and the type of alert.
  • A listing of missing children from NCMEC organized by the states from where they are missing.
  • A listing of missing children from NCMEC reported missing in proximity to your current location.
  • The ability to share the active AMBER Alerts via Twitter, Facebook, Email, and SMS messages.

If a user has information about a case or has seen one of the missing children, they can press a button and automatically call NCMEC’s toll-free 24-hour hotline 1-800-THE-LOST (800-843-5678), or contact the local authority in charge of the missing child case.
Although this application includes a listing of all active AMBER Alerts, it does not currently actively notify the user when a new AMBER Alert is issued (Live Tile feature coming soon). For active notification, NCMEC encourages all wireless subscribers to register to receive Wireless AMBER Alerts™. Through that initiative, they can sign up at to receive text message notices about AMBER Alerts that have been issued in their area.
Please consider downloading the Amber Central Application and signing up for Wireless AMBER Alerts. You might be able to help an abducted or missing child come home safely. For other ways that you can get involved, please visit NCMEC’s website here.

Check out the video walk-through of Amber Central below.

I had some great resources that made Amber Central possible.  Many thanks to:

Ramesh – My colleague at work.  For great input and advice.  Extremely great guy to be working with.  He has also successfully published his apps (discountCalc & Health Caddy).

Telerik – For their “Rad” Windows Phone controls.

Laurent Bugnion, Microsoft MVP (Silverlight) creator of MVVMLight, a Model-View-View-Model framework for WPF, Silverlight and Windows Phone 7 applications. Always enjoy working with MVVMLight, AND

National Center for Missing & Exploited Children® (NCMEC) – For the great Amber Alert Feeds

Download Amber Central

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Easy Diary for Windows Phone 7

I have always wanted to get into the mobile space.  Particularly with developing apps.  So when the Windows Phone 7 was announced, as a newbie Silverlight developer (a year ago), I thought this would be a great chance to do so.  And so, I dove in.

The Win Phone 7, a Silverlight & XNA developer platform makes it fairly easy for current Silverlight/XNA developers to transition into the mobile space.  And I have to say, it’s been very exciting.

Easy Diary, a diary/journal application, was my first (of many apps to come) for the Windows Phone 7.  It gives potential users a quick and easy way to record moments throughout their day.  They can also connect with popular social sites like Twitter & Facebook, and display their online activity as part of their diary.  The app took about two weeks of total work, and was released to the Windows Marketplace a few months ago prior to the release of the phone. 

I will soon be posting more info on my current and future apps on my site here.  In the meantime, you can click here to view my app in the marketplace (Zune software required).  There was also a small article posted about my app here.

While I would like to say I figured everything out on my own while developing my app, that just won’t be right.  So I have to give credit where credit is due.  See below for credit(s), resources, and screenshots of the app.


Laurent Bugnion created a very light, flexible and versatile MVVM framework for the Windows Phone 7 (dubbed MVVM Light), Silverlight, and WPF.  It made my life very easy while developing this app and it will come in very handy in the many apps to come.


There are many valuable resources pertaining to developing apps for the Windows Phone.  Ranging from beginner to expert levels.  Here are just a few of them:


There are currently over 3,000 apps in the windows marketplace, and it’s going to be very exciting to see many talented developers come up brilliant ideas and even more great apps in times to come.

Good move Microsoft…good move.

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