How do I use DropDownList in Xamarin?

How can we use Dropdown in Xamarin.Forms?

As we said before, rejecting  the Android operating system  is a slider control called Spinner. In other words, Xamarin. Forms Control is a special package that can be used for the platform. If we want to tell you better, let's give an example: Xamarin. Forms Entry is an EditText package that can be used in applications developed for the Android operating system ( in Slovak:  aplikácie vyvinuté pre operačný systém Android  )and platform, as well as UITextField in iOS.

The steps for creating a Dropdown slider are as follows:

- I must first  create a new project in Xamarin.Forms.

- Then, we must create a Dropdown view in Xamarin.Forms .NET Standard Project to make the relevant settings after that.

- Next, in the Android project, to control Dropdown, we must turn on Spinner.

- Then, we must implement the settings related to it and simulate and test the trial version for the Android platform.

1- In the first step, we must create a project related to Xamarin.Forms. To do this, go to New - Project - Xamarin Cross-Platform App and then click OK to confirm.

2- Then, I select Android and  iOS platforms.

3- The dropdown view should be selected in Xamarin.Forms .NET.

4- To do this, I created a class called Dropdown. Of course, you must note that you inherit Dropdown with View. If it does, it means that Dropdown is the child of Dropdown.

5- In the next steps, we must create all the features that can be connected.

ItemsSource: This feature is used to assign a list of data that must be placed in Dropdown and filled.

- SelectedIndex:

This feature can also identify a list of values ​​selected from SourceSource items.

- ItemSelected:

This feature can also be used to perform an action when an item is selected in Dropdown.

 6- Like the following, we need to create a connectable property for ItemsSource.

 7- Next, we need to create a connectable property for SelectedIndex.

8- In the next steps, we need to create a custom ItemSelected event for dropdown control and event calling.

public event EventHandler ItemSelected.
public void OnItemSelected (int pos)
{
ItemSelected? .Invoke (this, new ItemSelectedEventArgs () {SelectedIndex = pos}).
}

9- As shown below, ItemSelectedEventArgs is a child of EventArgs.

10- Below is all the complete code that has been used to create the Dropdown.

11- Then, we must be able to package Spinner in  the Android project  and platform for Dropdown control.

12- To do this, we need to create a class file in the Android project called DropdownRenderer. Then add View Renderer.

13- After that, we must cancel OnElementChanged and OnElementPropertyChanged.

14- In ViewRenderer, we must configure Native Control using the SetNativeControl () method, as shown below.

15- Then, we must move from  Xamarin.Forms Dropdown  to Android Spinner control.

16- Select the default selection from the list of selected items.

17- We need to create an event for the selected item for the Spinner.

18- After creating the event required for the Dropdown, call.

 19- By changing OnElementPropertyChanged, we must assign ItemsSource & SelectedIndex to Android Spinner.

20- To link the dropdown view in the standard .NET project to the Export project, add the Android Client to the top of the namespace.

21- The complete code related to the steps listed above to create a Dropdown Renderer is as follows:

22- In the final stages, we should implement Dropdown and create a test version for the Android platform and operating system.

In these sections, we must use View in the Xamarin.Forms section.

23- We must open the designer file in MainPage.xaml.

24- You must set ItemsSource and SelectedIndex.

25- We need to add the selection event for the Dropdown.

26- The complete codes related to all the above steps are as follows: