Category : Android CSharp MonoDroid Visual Studio Xamarin
Creating a custom alert view in Android using C#
July 1, 2015
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As mentioned in my earlier post, we can use the default AlertDialog class to display the alerts of screen by setting different properties and methods of it. But still there sounds like, we may need dialogs on screen which would be needed to be customized. They can be accept user inputs, can display an arranged info of an user etc.
How to do it ?
We will follow few simple steps
- Create a custom view
- Render the custom view in AlertDialog
Create a custom view
Let’s add a new layout to the project under Resources > layout.
Quick Tips : Displaying an Alert in Android using MonoDroid
Displaying an informational alert on screen
Let’s just display a quick informative popup, which will only display an alert on screen with a title and a message in it. It actually gets closed when the back button get touched.
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AlertDialog.Builder alert = new AlertDialog.Builder(this); alert.SetMessage("This is just an alert to show on the screen in order to try my alert demo."); alert.SetTitle("Alert Clicked"); alert.Show(); |
Let’s display the OK and Cancel button
We will add OK and Canel button. On click of the buttons, it will display a quick Toast message on screen in order
to differentiate which button is clicked.
A simple way to show listview in Android using Xamarin
Ways to do it
There are basically 2 ways to do it in Android.
- Using the Listview control
- Using the ListActivity
By using ListActivity
In this way we don’t need to define any Listview in our AXML page. Just few lines of code will do it.
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
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
