Create android spinner dynamically in Xamarin

Question

I am creating a simple application to get familiar with Xamarin. I want to create and populate a spinner and display its options dynamically. I have seen the documentation here but it is not created programmatically. Any help will be appreciated

var levels = new List<String>() { "Easy", "Medium", "Hard", "Multiplayer" };
var adapter = new ArrayAdapter<String>(this, Android.Resource.Layout.SimpleSpinnerItem, levels);
                    adapter.SetDropDownViewResource(Android.Resource.Layout.SimpleSpinnerDropDownItem);
var spinner = FindViewById<Spinner>(Resource.Id.spnrGameLevel);
spinner.Adapter = adapter;

spinner.ItemSelected += (sender, e) =>
{
    var s = sender as Spinner;
    Toast.MakeText(this, "My favorite is " + s.GetItemAtPosition(e.Position), ToastLength.Short).Show();
};

My axml file

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Choose your game level" />
    <Spinner
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:id="@+id/spnrGameLevel" />
</LinearLayout>

Solution

To dynamically create items for Spinner, you need to have an adapter.

The simplest adapter would be ArrayAdapter<T>.

Here is the example.

var items = new List<string>() {"one", "two", "three"};
var adapter = new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleSpinnerItem, items);

After setting up the adapter, find the Spinner in your view and set adapter to it.

var spinner = FindViewById<Spinner>(Resource.Id.spinner);
spinner.Adapter = adapter;

Comments

[Anand]

Thanks for your answer. I have tried the same, but getting an exception while tried this. Object Reference not set to an instance of an object. I have updated the my question with code

[Aaron He]

@Anand Which statement caused the exception?

[Anand]

Exception occurs in spinner.Adapter = adapter;

[Aaron He]

@Anand Did you forget to instantiate the view contains the spinner?

[Anand]

No, I have instantiated the view

[Aaron He]

@Anand It's weird. I tried the same thing, just adding SetContentView(Resource.Layout.Main); in OnCreate method. And it works.

[Mohammad Sina Karvandi]

It's because spinner is not invoked ,,, you should put SetContentView(Resource.Layout.Main); before using var spinner = FindViewById<Spinner>(Resource.Id.spinner);