Xamarin.Android multiple generic lists in RecyclerView

Question

Situation: I'm having a list of countries. Within this lists I'll have a list of cities. I want to represent a cardview for each country that shows the cities.

Country.cs

public class Country
{
    public int CountryId { get; set; }
    public string Description { get; set; }
    public string Flag { get; set; }
    public IList<City> Cities { get; set; }
}

City.cs

public class City
{
    public int CityId { get; set; }
    public string Description { get; set; }
    public int Population { get; set; }
}

MainActivity.cs

public class MainActivity : Activity
{
    public IList<Country> Countries = new List<Country>();
    public IList<City> CitiesBelgium = new List<City>();
    public IList<City> CitiesGermany = new List<City>();

    RecyclerView recyclerView;
    RecyclerView.LayoutManager layoutManager;
    CountryAdapter countryAdapter;
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);

        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.Main);

        PopulateList(); //this will populate the desired lists in this example

        recyclerView = FindViewById<RecyclerView>(Resource.Id.recyclerView);
        layoutManager = new LinearLayoutManager(this);
        recyclerView.SetLayoutManager(layoutManager);

        countryAdapter = new CountryAdapter(Countries);
        recyclerView.SetAdapter(countryAdapter);
    }
}

CountryAdapter.cs

public class CountryAdapter : RecyclerView.Adapter
{
    IList<Country> countries;
    public override int ItemCount
    {
        get { return countries.Count; }
    }

    public CountryAdapter(IList<Country> countries)
    {
        this.countries = countries;
    }

    public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)
    {
        CountryViewHolder vh = holder as CountryViewHolder;
        vh.Id.Text = countries[position].CountryId.ToString();
        vh.Description.Text = countries[position].Description;
    }

    public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)
    {
        View itemView = LayoutInflater.From(parent.Context).
                Inflate(Resource.Layout.CountryCardView, parent, false);
        CountryViewHolder vh = new CountryViewHolder(itemView);
        return vh;
    }
}

CountryViewHolder.cs

public class CountryViewHolder : RecyclerView.ViewHolder
{
    public TextView Id { get; private set; }
    public TextView Description { get; private set; }

    public CountryViewHolder(View itemView) : base(itemView)
    {
        Id = itemView.FindViewById<TextView>(Resource.Id.textViewId);
        Description = itemView.FindViewById<TextView>(Resource.Id.textViewDescription);
    }
}

This is working and I get a cardview for each country. But what is the best way to get the list of cities in the cardview of the country?

In Xamarin.Forms you can group items. I don't think this is possible with RecyclerView? Example: https://dzone.com/articles/xamarin-forms-grouping-enabled-listview

Hi, hope this helps! 1. thing: Currently, you are setting the ItemCount to "2" - for each of your countries - but this mean, that you will only draw "2" cells. You need this to include both "header/country" cells, and "city" cells. — Mathias Kirkegaard
– Mathias Kirkegaard, Commented Feb 5, 2018 at 13:31
2. override "GetItemViewType(int position)" and define wheter it is a Header or a City (indicate with an integer or enum) — Mathias Kirkegaard
– Mathias Kirkegaard, Commented Feb 5, 2018 at 14:57
3. In "RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)" you will create the viewholder based on the viewtype. — Mathias Kirkegaard
– Mathias Kirkegaard, Commented Feb 5, 2018 at 14:58
4. in "OnBindViewHolder(RecyclerView.ViewHolder holder, int position)" you cast to Header or City (based on the type of the holder). And then you populate the holder with data. — Mathias Kirkegaard
– Mathias Kirkegaard, Commented Feb 5, 2018 at 15:02
4.1: but the data you put in is like: "cell at pos 0" -> Country name belgium... "cell at pos 2" -> City data Ghent... "cell at pos 3" -> Country name Germany... — Mathias Kirkegaard
– Mathias Kirkegaard, Commented Feb 5, 2018 at 15:04

York Shen · Accepted Answer · 2018-02-06 07:12:11Z

2

I'm having a list of countries. Within this lists I'll have a list of cities. I want to represent a cardview for each country that shows the cities.

You could use ExpandableListView to implement this feature:

A view that shows items in a vertically scrolling two-level list. This differs from the ListView by allowing two levels: groups which can individually be expanded to show its children. The items come from the ExpandableListAdapter associated with this view.

Here is the example.

answered Feb 6, 2018 at 7:12

York Shen

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3 Comments

JeffreyM Over a year ago

Thanks for your comment. I think this will help me a lot. But can you also implement more levels than only 2? In my real world application I need 3 levels of data. Grouping - detail - and a list of a the detail.

York Shen Over a year ago

@JeffreyM, this example is 3 levels of data, :).

York Shen Over a year ago

@JeffreyM, and you could refer to this: stackoverflow.com/questions/42627161/…, hope this ca help you.

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