GUTSchedule/GUT.Schedule/GUTSchedule.Droid/Fragments/DatePickerFragment.cs

using System;
using Android.OS;
using Android.Widget;
using Android.App;
using System.Threading.Tasks;
using Android.Content;

namespace GUTSchedule.Droid.Fragments
{
	/// <summary>
	/// Date picker
	/// </summary>
	public class DatePickerFragment : Android.Support.V4.App.DialogFragment, DatePickerDialog.IOnDateSetListener
	{
		DateTime _date;
		bool dismissed = false;
		public override Dialog OnCreateDialog(Bundle savedInstanceState) =>
			new DatePickerDialog(Activity, this, _date.Year, _date.Month - 1, _date.Day);

		// Occures when user selected a date
		public void OnDateSet(DatePicker view, int year, int month, int dayOfMonth)
		{
			_date = view.DateTime;
			dismissed = true;
		}

		public override void OnCancel(IDialogInterface dialog)
		{
			base.OnCancel(dialog);
			dismissed = true;
		}

		/// <summary>
		/// Shows date picker and waits for user input
		/// </summary>
		/// <param name="manager">Fragment manager of the current activity (In most common cases it is <c>this.FragmentManager</c>)</param>
		/// <param name="date">Date which is to be selected by default</param>
		/// <returns><see cref="DateTime"/> picked by user</returns>
		public async Task<DateTime> GetDate(Android.Support.V4.App.FragmentManager manager, DateTime date)
		{
			_date = date;
			Show(manager, "datePicker");

			while (!dismissed)
				await Task.Delay(100);

			return _date;
		}
	}
}