Category : CSharp iOS Visual Studio Xamarin
[Released] : Xamarin support for Apple Watch Kit
March 13, 2015
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Apple announced the Smart Watch last week !!! What is Apple Watch ?? A smart watch to run in-built apps, download and run store apps, connect people, keeps track of health & fitness, keeps timing etc. Just more than a normal watch. Can we develop apps for this ?? Yes, we can. What are the
Child control Event handling in Listview using Xamarin.Forms
We can add child controls to Listview in Xamarin.Forms. In order to see the child control in action we will take an example. Let’s display a list of data in the Listview and perform delete option on the list data per row basis.
Since we need to add multiple columns in the list view, we need to use the DataTemplate to define the custom view. Let’s use a model class to assign the data to the custom view.
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public class Item { public string ItemName { get; set; } public string ItemDetails { get; set; } } |
We will use XAML to design a Listview
In the above XAML, we have used the StackLayout as the parent container for the child views. It contains a Label and a Listview. UI Control is ready.
Time to add event to the child control
We will replace the Button control in the above XAML with the following line
Display requirement specific keyboard using Xamarin.Forms
Xamarin uses the Keyboard class to show different virtual keyboards depending upon the user request. It contains several static properties to create different kind of virtual keyboards. Xamarin displays the Default Keyboard, if nothing is specified.
Keyboard for Chatting
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MainPage = new ContentPage() { Content = new StackLayout() { Children = { new Entry() { Keyboard = Keyboard.Chat } } } }; |
It opens up the default virtual keyboard in the device, which would be convenient for chatting, having few extra keys.
Using a Scrollview in XamarinForms
What is it ???
The short answer is ScrollView is a Layout. But it can only contain a single Visual Element in its Content property.
Why So ???
Because, the Layouts such as Stack, relative etc. are derived from Layout<T> generic class. This Layout<T> generic class is derived from the Layout class, which is a non-generic class.
ScrollView is inherited from the Non-generic Layout class. That is the same reason, why it does not support a generic way to add children. It only exhibits the Content property to accept a single view or a Layout.
Usage by example
Usage Example #1 : Let’s display a paragraph of scrolling text
Customizing Listview display in Xamarin
As the usual behavior of ListView to display the items in a list and it contains a single column. The ItemSource property of Listview accepts the list of data to be displayed and render the same on screen.
The code for a simple list to display the Students of a class would like as in the following pic.
Now let’s customize this ListView in a way to display the Student Name along with the Class and School they belongs to.
As in the image above, the data contains a single record. So to accommodate the data in a single record, Let’s create a Student model class.
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public class Student { public string StudentName { get; set; } public string Class { get; set; } public string School { get; set; } } |
In order to customize the ListView display, we need to override the ViewCell class.
What’s new in Xamarin.Forms 1.3 : Inherited App Class
With the new release of Xamarin.Forms 1.3 version, the App Class has its new Avatar. The Older version of App Class was just a class with static methods. Unlike the older version, the new version is an inherited class from the Xamarin.Forms.Application class. Summary of improvements Addition of new life cycle events : We can
Consuming RESTFul web Service in XamarinForms project Using HttpClient
Web service is an important part of the mobile app. I am trying to consume a RESTFul web service in Xamarin using HttpClient. Prerequisites : – Microsoft.Net.Http – Newtonsoft.Json In this example, let’s display the name of the places for a given postal code. We will use the http://api.geonames.com webservice to get the places. Call
Xamarin.Forms.DependencyService platform tweaks
What is DependencyService in Xamarin ?
DependencyService is a static class under Xamarin.Forms namespace. Shared or Portable projects can access the platform based tweaks that are done in any specific platform projects by using DependencyService.
How it works?
The key point is by defining an Interface.
- Declare an Interface in the Shared / Portable project.
- Implement the interface in platform specific projects.
- Register the class under DependencyService Assembly with Dependency attribute.
- Call the DependencyService.get method with the Interface. It will identify the platform and executes the implementation
Xamarin.Mobile : Cross platform component for Device APIs
Xamarin.Mobile is a component from Xamarin to write a commonly used code to consume the device API. What I meant by the commonly used code is, the same code that will can access device specific APIs and behave accordingly depending upon the platform in which it is running.
More than a month back newest release of Xamarin.Mobile is still in its preview release mode.
As of now, it supports the following device APIs for iOS, Android and Windows Phone.
- Contacts
- Geolocation
- Media
How it compiles in Xamarin
What we must agree is, different platforms have different ways of understanding the assemblies. They execute and run the app in the same way. So Xamarin compiles the app in relevance to the platforms basing upon their nature and behavior of executing the assemblies. So that the app assembly fits to the platform acceptable format and run.
Compiling for iOS
iOS runs on ARM architecture. So the nature of iOS is, it understands the assembly language for ARM. It never allows the code to be generated dynamically during run time. So to respect the same, Xamarin did it exactly. It uses the Ahead Of Time (AOT) compilation process in order to generate ARM assemblies from the static code. This is a process to generate the pre-compiled code. Unlike the traditional on-demand execution approach, it compiles the code before hand. During the linking process, it links the .Net framework and the relevant assemblies only. It removes all others, which are no longer in use.