Xamarin.Forms: using the PanGestureRecognizer

Recently I’ve blogged about Xamarin.Forms and how to create a XAML Behavior for enabling Multi-Touch gestures to generic elements and implementing a scale / pinch functionality.

Fortunately the framework provides three types of recognizer that greatly simplify the implementation:

  • PinchGestureRecognizer allows user interactions for zoom / scale functionalities;
  • PanGestureRecognizer enables pan / translate transformations;
  • TapGestureRecognizer detects tap events.

Yesterday I decided to try the PanGestureRecognizer for extending the capabilities of the Behavior described in the previous post.

First of all, I added two Bindable properties in order to permit activation / deactivation of individual gestures (Bindable properties are equivalent to Dependency ones in UWP XAML)

In this way we can specify in our XAML what gestures are enabled:

Then I initialised the GestureRecognizers adding a new PanGestureRecognizer to the recognizers list:

And subscribed to the PanUpdated event in order to apply the translate transform:

The implementation of this event handler permits to update the X and Y coordinates of the element when a Pan gesture is detected:

Here we go: the sample app can now be deployed to the emulators and iOS / Android / Windows devices.

Just a couple of notes:

  • deployment to iOS required this workaround to work properly since the new sample app uses different assemblies;
  • Tap gestures on Android requires Xamarin.Forms – minimum version v2.1.0.6501-pre1 as pointed by the official documentation.

As usual, the latest source code is available for download on GitHub.

Having fun with Xamarin.Forms and Multi-Touch Behaviors

Recently Xamarin has released preview support for the Universal Windows Platform in their Xamarin.Forms framework so I have been playing around with version 2.0 for testing its features and verify how easy is to target multiple platforms (iOS, Android, Windows 10 UWP, Windows Phone, Windows 8.1) with a single codebase.

One of the experiments I have done is related to custom multi-touch gestures: the idea to use a XAML Behavior is a common scenario to write well structured code so I started creating a new Cross-Platform Xamarin.Forms Portable project and upgraded the NuGet packages to the latest stable version of the framework (currently v2.0.1.6505).

I have then read the official documentation and analysed the samples available on GitHub: a very good example is the PinchGesture one so, starting from it, I created a new MultiTouchBehavior implementing this gesture and attached the same Behavior to an Image object added to a sample ContentPage, as described below in this lovely cross-platform XAML 🙂

The BindingContext=”{Binding}” is used to trigger the BindingContextChanged event and initialise correctly the GestureRecognizers  for the parent object since the AssociatedObject.Parent is set to null when the Behavior.OnAttachedTo() is called (I suppose that the XAML tree is not yet completely created when the behavior is attached in Xamarin.Forms):

Here is the project deployed to the Android, iOS and Windows 10 emulators:

MultiTouch_Android_Emulator   Simulator Screen Shot 14 Feb 2016, 18.25.00   MultiTouch_Windows10_Emulator

I’ve been particularly impressed by Xamarin.Forms: the possibility to target so many platforms using the same code is a killer feature and the development environment is also very comfortable to use.

The sample code used in this post is available on GitHub, I’m planning to add more functionalities in the future with particular regard to other common multi-touch gestures using Xamarin.Forms and XAML.

TypedMVVM samples for Windows 10 UWP and IoC fixes

A new version of the TypedMVVM samples is now available on CodePlex and contains a basic sample targeting Windows 10 UWP.

The repository also contains a fix for the basic IoC container: now the code correctly handles the register<T>() and resolve<T>() functions and populates the internal dictionary of object instances

My friend Lee has also pushed to GitHub a new sample using TypedMVVM for web apps here: check it out!

NDepend v6 available

Version 6 of NDepend is now available for download from the official site.

New features include:

  • enhanced Visual Studio integration;
  • support for Visual Studio 2015;
  • rule files shareable amongst projects;
  • default rules description and HowToFix;
  • default rules less false positives;
  • colored code metric view;
  • intuitive display of code coverage percentage;
  • compiler generated code removal;
  • async support;
  • analysis enhancements;
  • support for Visual Studio Blue, Dark, Light themes;
  • support for high DPI resolution;
  • integration with TFS, SonarQube and TeamCity.

A detailed description of the new capabilities is available here.

Cordova Windows Store apps and certificate expired error

I was updating TypedMVVM to the latest Visual Studio 2013 Update 4 and Cordova tools (using the new free Community Edition) and trying to deploy the sample to the Windows 8 emulator when I received the following

error APPX0108: The certificate specified has expired

As pointed here by Microsoft Open Technologies, the certificate available in the Visual Studio template has just expired and is not possible to deploy Windows Store apps using the old one.

To solve this problem I’ve then downloaded from here the updated certificate and copied to the following location inside the Visual Studio project:

res/native/windows/CordovaApp_TemporaryKey.pfx

The updated code is available for download on CodePlex.

WinJS and TypeScript: binding a ListView itemDataSource to a ViewModel property

I’ve recently been asked on the TypedMVVM forums how to properly bind a ListView data source to a list of items available as a property in the ViewModel.

Just create new getters and setters in the ViewModel and initialise the property by creating a new instance of WinJS.Binding.List:

Then reference from HTML the new itemsSource property in the ListView control using data-win-bind:

As usual, the sample code is available for download on Codeplex.

TypedMVVM: Adding a new IoC.Container class for generating instances using generics

In the previous days I was extending my TypedMVVM library with additional classes for separating the logic and being able to use different services for handling operations like showing message dialogs.

I’ve then started the implementation of a simple IoC.Container class that will manage in a centralized way the creation of new objects (ViewModels, Services, etc.) used by the application.

The first step was the creation of a simple Resolve<T> method for creating instances using the concept of Generics available in TypeScript.

When working with factories and generics, it’s necessary to refer to class types using their constructor function:

In this way, a new instance of type T will be returned each time the function IoC.Container.resolve will be used.

For example, it’s now possible to inject a service on a ViewModel in this way:

I’m planning for the future more functionalities for this IoC.Container class, like the possibility to register specific services with interfaces and use them as singletons.

The updated code is available for download from the repository here.

WinJS – Adding a reference to an existing Universal shared project from your Windows Store / Windows Phone app

In the past days I was trying to reference an existing “Universal Shared” project from a Windows Store app, but it seems like that the “Add Reference” functionality is still not available on Visual Studio for shared projects when using WinJS or generic JavaScript Universal apps.

I’ve then verified the default Universal apps template and found that every project is referencing the “Shared” one using this Import block in the .jsproj file:

To enable it for your project, just open the “Solution Explorer” in Visual Studio and:

  • right-click the project and select “Unload Project“;
  • select “Edit <Your-Project-Name>.jsproj“;
  • add the “Import Project” block using the code editor and save it;
  • right-click and select “Reload Project“.

The shared project code should now be correctly referenced and available in your original app.

Same technique can obviously be used by Windows Phone 8.1 solutions (or other targets / platforms).

NDepend v5.0 available

I’ve just received my copy of NDepend v5.0: this new version adds several great features to the product including

  • Support for Visual Studio 2013 (yeah!)
  • New Dashboard Panel
  • Focusing on Recent Rules violation
  • UI Enhancements
  • Trend Monitoring
  • Churning Rules and Queries
  • Report Enhancements

Click here to read a detailed description of the new capabilities and access the download links (14 days trial available).

Happy coding!

NDepend v4.1 adds CQLinq killer feature and support for Windows Store apps

I already blogged about NDepend basic features here: I was positively impressed by the capabilities of this tool by fellow MVP Patrick Smacchia.

NDepend permits you to examine .NET projects and highlight different metrics in the code in order to better analyse what areas of your solution needs refactoring for improving performance, code maintainability, application stability and applying best coding practices (just to name a few).

Some features, already available in the previous versions of NDepend, include tools for visually representing dependencies between classes, defining custom rules on code, explore code diffs and analyse code coverage. These ones are particularly helpful when the size of the project grows: a visual representation helps the developer to better identify areas that needs more work (and then save development time).

Recently Patrick contacted me for highlighting the new features available in NDepend v4.1. I was very pleased to find support for Windows Store apps but another capability got immediately my attention: CQLinq.

This is a killer feature: CQLinq (acronym for Code Query LINQ) enables the developer “to query the code” for retrieving information about it. Some simple examples of queries could be:

  • find me the methods too big / too complex;
  • find the methods added but poorly covered by tests;
  • get information about naming conventions;
  • any other query you like: the possibilities are not limited at all!

Technically these queries can be constructed using the traditional LINQ syntax and the types defined in the NDepend.CoreModel of the NDepend API.

The best place to start using CQLinq is here by exploring the dedicated section on the site which contains a ton of different examples to start: I recommend to try and run the available samples which are an excellent starting point and then modifying them for custom queries.

I’ve been really impressed by CQLinq and I can’t wait to use it on real projects to enhance the quality of the code and then reduce the time needed for new implementations.

Happy coding everyone!