Arrange List by Distance [Xamarin]

Vegeta ZA

New member
Joined
Feb 15, 2017
Messages
3
Programming Experience
Beginner
Hi Everyone,
The app that I am working on currently has user details stored in a db and if you click on any user it will show you their details and also their location pin pointed on a map below their details.
What I want the app to do is use my current location and then display the users who are within 10kms from me by comparing my location to all of those in the db and then displaying only the ones which fall into the category <= 10kms from me.
How would I be able to make it compare to each address in the db and then display only the nearest people based on my location to their's?
Here is the code for the class that adds the details from the db to the form and also does the geo coding:

C#:
[COLOR=#222222][FONT=Verdana]using System;
[/FONT][/COLOR][COLOR=#222222][FONT=Verdana]using System.Collections.Generic;[/FONT][/COLOR]
C#:
using System.Linq;
using System.Threading.Tasks;
using Acquaint.Abstractions;
using Acquaint.Models;
using Acquaint.Util;
using Android.App;
using Android.Content;
using Android.Gms.Maps;
using Android.Gms.Maps.Model;
using Android.Locations;
using Android.OS;
using Android.Support.V7.App;
using Android.Transitions;
using Android.Views;
using Android.Widget;
using Microsoft.Practices.ServiceLocation;
using Plugin.ExternalMaps;
using Plugin.ExternalMaps.Abstractions;
using Plugin.Messaging;
using Toolbar = Android.Support.V7.Widget.Toolbar;
namespace Acquaint.Native.Droid
{








    /// <summary>
    /// Acquaintance detail activity.
    /// </summary>
    [Activity]
    public class AcquaintanceDetailActivity : AppCompatActivity, IOnMapReadyCallback
    {






        IDataSource<Acquaintance> _DataSource;
        Acquaintance _Acquaintance;
        string _AcquaintanceId;
        ImageView _GetDirectionsActionImageView;
        LatLng _GeocodedLocation;


        View _MainLayout;
        Bundle _SavedInstanceState;


        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);


            _SavedInstanceState = savedInstanceState;


            _MainLayout = LayoutInflater.Inflate(Resource.Layout.AcquaintanceDetail, null);


            SetContentView(_MainLayout);


            SetSupportActionBar(FindViewById<Toolbar>(Resource.Id.toolbar));


            Title = SupportActionBar.Title = "";


            // ensure that the system bar color gets drawn
            Window.AddFlags(WindowManagerFlags.DrawsSystemBarBackgrounds);


            // enable the back button in the action bar
            SupportActionBar.SetDisplayHomeAsUpEnabled(true);
            SupportActionBar.SetHomeButtonEnabled(true);
        }


        protected override async void OnResume()
        {
            base.OnResume();


            _DataSource = ServiceLocator.Current.GetInstance<IDataSource<Acquaintance>>();


            // extract the acquaintance id from the intent
            _AcquaintanceId = Intent.GetStringExtra(GetString(Resource.String.acquaintanceDetailIntentKey));


            // fetch the acquaintance based on the id
            _Acquaintance = await _DataSource.GetItem(_AcquaintanceId);


            // set the activity title and action bar title
            Title = SupportActionBar.Title = _Acquaintance.DisplayName;


            SetupViews();


            SetupAnimations();
        }


        void SetupViews()
        {
            // inflate the content layout
            var contentLayout = _MainLayout.FindViewById<LinearLayout>(Resource.Id.acquaintanceDetailContentLayout);


            contentLayout.InflateAndBindRemoteImageView(Resource.Id.profilePhotoImageView, _Acquaintance.SmallPhotoUrl);


            // inflate and set the name text view
            contentLayout.InflateAndBindTextView(Resource.Id.nameTextView, _Acquaintance.DisplayName);


            // inflate and set the company name text view
            contentLayout.InflateAndBindTextView(Resource.Id.companyTextView, _Acquaintance.Company);


            // inflate and set the job title text view
            contentLayout.InflateAndBindTextView(Resource.Id.jobTitleTextView, _Acquaintance.JobTitle);


            contentLayout.InflateAndBindTextView(Resource.Id.streetAddressTextView, _Acquaintance.Street);


            contentLayout.InflateAndBindTextView(Resource.Id.cityTextView, _Acquaintance.City);


            contentLayout.InflateAndBindTextView(Resource.Id.statePostalTextView, _Acquaintance.StatePostal);


            contentLayout.InflateAndBindTextView(Resource.Id.phoneTextView, _Acquaintance.Phone);


            contentLayout.InflateAndBindTextView(Resource.Id.emailTextView, _Acquaintance.Email);


            _GetDirectionsActionImageView = contentLayout.InflateAndBindLocalImageViewByResource(Resource.Id.getDirectionsActionImageView, Resource.Mipmap.directions);
            _GetDirectionsActionImageView.Visibility = ViewStates.Invisible;
            _GetDirectionsActionImageView.Click += async (sender, e) => {
                if (_GeocodedLocation != null)
                    // we're using the External Maps plugin from James Montemagno here (included as a NuGet)
                    await CrossExternalMaps.Current.NavigateTo(_Acquaintance.DisplayName, _GeocodedLocation.Latitude, _GeocodedLocation.Longitude, NavigationType.Driving);
            };


            var messageActionImageView = contentLayout.InflateAndBindLocalImageViewByResource(Resource.Id.messageActionImageView, Resource.Mipmap.message);
            messageActionImageView.Click += (sender, e) => {
                // we're using the Messaging plugin from Carel Lotz here (included as a NuGet)
                var smsTask = MessagingPlugin.SmsMessenger;
                if (smsTask.CanSendSms)
                    smsTask.SendSms(_Acquaintance.Phone.SanitizePhoneNumber(), "");
            };


            var phoneActionImageView = contentLayout.InflateAndBindLocalImageViewByResource(Resource.Id.phoneActionImageView, Resource.Mipmap.phone);
            phoneActionImageView.Click += (sender, e) => {
                // we're using the Messaging plugin from Carel Lotz here (included as a NuGet)
                var phoneCallTask = MessagingPlugin.PhoneDialer;
                if (phoneCallTask.CanMakePhoneCall)
                    phoneCallTask.MakePhoneCall(_Acquaintance.Phone.SanitizePhoneNumber());
            };


            var emailActionImageView = contentLayout.InflateAndBindLocalImageViewByResource(Resource.Id.emailActionImageView, Resource.Mipmap.email);
            emailActionImageView.Click += (sender, e) => {
                // we're using the Messaging plugin from Carel Lotz here (included as a NuGet)
                var emailTask = MessagingPlugin.EmailMessenger;
                if (emailTask.CanSendEmail)
                    emailTask.SendEmail(_Acquaintance.Email, "");
            };


            // inflate the map view
            var mapview = FindViewById<MapView>(Resource.Id.map);


            // create the map view with the context
            mapview.OnCreate(_SavedInstanceState);


            // get the map, which calls the OnMapReady() method below (by virtue of the IOnMapReadyCallback interface that this class implements)
            mapview.GetMapAsync(this);
        }


        void SetupAnimations()
        {


            if (Build.VERSION.SdkInt >= BuildVersionCodes.Lollipop)
            {
                var enterTransition = TransitionInflater.From(this).InflateTransition(Resource.Transition.acquaintanceDetailActivityEnter);


                Window.SharedElementEnterTransition = enterTransition;
            }
        }


        #region Implementations IOnMapReadyCallback


        public async void OnMapReady(GoogleMap googleMap)
        {
            // disable the compass on the map
            googleMap.UiSettings.CompassEnabled = false;


            // disable the my location button
            googleMap.UiSettings.MyLocationButtonEnabled = false;


            // disable the map toolbar
            googleMap.UiSettings.MapToolbarEnabled = false;


            // prevent tap gestures (this will automatically open the external map application, which we don't want in this case)
            googleMap.MapClick += (sender, e) => {
                // an empty delegate, to prevent click events
            };


            // attempt to get the lat and lon for the address
            _GeocodedLocation = await GetPositionAsync();


            if (_GeocodedLocation != null)
            {
                // because we now have coordinates, show the get directions action image view, and wire up its click handler
                _GetDirectionsActionImageView.Visibility = ViewStates.Visible;


                // initialze the map
                MapsInitializer.Initialize(this);


                // display the map region that contains the point. (the zoom level has been defined on the map layout in AcquaintanceDetail.axml)
                googleMap.MoveCamera(CameraUpdateFactory.NewLatLng(_GeocodedLocation));


                // create a new pin
                var marker = new MarkerOptions();


                // set the pin's position
                marker.SetPosition(new LatLng(_GeocodedLocation.Latitude, _GeocodedLocation.Longitude));


                // add the pin to the map
                googleMap.AddMarker(marker);
            }
        }


        #endregion


        async Task<LatLng> GetPositionAsync()
        {
            const string errorMessage = "Timed out waiting for response from server";


            IList<Address> addresses = new List<Address>();
            bool firstPassTimedOut = false;


            try
            {
                // asynchronously retrieve a geocoded location for the acqaintance's address
                addresses = await new Geocoder(this).GetFromLocationNameAsync(_Acquaintance.AddressString, 1);
            }
            catch (Exception ex)
            {
                if (ex.Message == errorMessage)
                {
                    firstPassTimedOut = true;
                    ShowGeocodingErrorAlert();
                }
            }


            // A quirk in the underlying Android geocoding API (not Xamarin.Android) sometimes prevents 
            // valid addresses from returning coordinates unless the address number is rounded to a multiple of ten.
            // So, if we don't get coordinates on the first pass, we try a second time with a rounded address number.




            if (addresses.Count > 0)
            {


                return new LatLng(addresses.First().Latitude, addresses.First().Longitude);
            }
            else if (!firstPassTimedOut && addresses.Count == 0 && AddressBeginsWithNumber(_Acquaintance.AddressString))
            {
                try
                {
                    addresses = await new Geocoder(this).GetFromLocationNameAsync(GetAddressWithRoundedStreetNumber(_Acquaintance.AddressString), 1);
                }
                catch (Exception ex)
                {
                    if (ex.Message == errorMessage)
                    {
                        ShowGeocodingErrorAlert();
                    }
                }


                if (addresses.Count > 0)
                {
                    return new LatLng(addresses.First().Latitude, addresses.First().Longitude);
                }
            }


            return null;
        }


        void ShowGeocodingErrorAlert()
        {
            // as long as this activity is not yet destroyed, show an alert indicating the gecooding error
            if (!IsDestroyed)
            {
                //set alert for executing the task
                var alert = new Android.App.AlertDialog.Builder(this);


                alert.SetTitle("Geocoding Error");


                alert.SetMessage("An error occurred while converting the street address to GPS coordinates.");


                alert.SetPositiveButton("OK", (senderAlert, args) => {
                    // an empty delegate body, because we just want to close the dialog and not take any other action
                });


                //run the alert in UI thread to display in the screen
                RunOnUiThread(() => {
                    alert.Show();
                });
            }
        }


        void ShowDeleteConfirmationAlert()
        {
            // as long as this activity is not yet destroyed, show an alert for confirming the delete action
            if (!IsDestroyed)
            {
                //set alert for executing the task
                var alert = new Android.App.AlertDialog.Builder(this);


                alert.SetTitle("Delete?");


                alert.SetMessage($"Are you sure you want to delete {_Acquaintance.FirstName} {_Acquaintance.LastName}?");


                alert.SetPositiveButton("Delete", async (senderAlert, args) => {
                    await _DataSource.RemoveItem(_Acquaintance);
                    OnBackPressed();
                });


                alert.SetNegativeButton("Cancel", (senderAlert, args) => {
                    // an empty delegate body, because we just want to close the dialog and not take any other action
                });


                //run the alert in UI thread to display in the screen
                RunOnUiThread(() => {
                    alert.Show();
                });
            }
        }


        public override bool OnCreateOptionsMenu(IMenu menu)
        {
            MenuInflater.Inflate(Resource.Menu.AcquaintanceDetailMenu, menu);


            return base.OnCreateOptionsMenu(menu);
        }


        public override bool OnOptionsItemSelected(IMenuItem item)
        {
            if (item != null)
            {
                switch (item.ItemId)
                {
                    case Android.Resource.Id.Home:
                        // execute a back navigation
                        OnBackPressed();
                        break;
                    case Resource.Id.acquaintanceEditButton:
                        StartActivity(GetEditIntent());
                        break;
                    case Resource.Id.acquaintanceDeleteButton:
                        ShowDeleteConfirmationAlert();
                        break;
                }
            }


            return base.OnOptionsItemSelected(item);
        }


        Intent GetEditIntent()
        {
            // setup an intent
            var editIntent = new Intent(this, typeof(AquaintanceEditActivity));


            // Add some identifying item data to the intent. In this case, the id of the acquaintance for which we're about to display the detail screen.
            editIntent.PutExtra(Resources.GetString(Resource.String.acquaintanceDetailIntentKey), _Acquaintance.Id);


            return editIntent;
        }


        // determines if the address begins with a number
        static bool AddressBeginsWithNumber(string address)
        {
            return !String.IsNullOrWhiteSpace(address) && Char.IsDigit(address.ToCharArray().First());
        }


        // returns a street address with the number portion rounded to the closest tens place.
        static string GetAddressWithRoundedStreetNumber(string address)
        {
            var endingIndex = GetEndingIndexOfNumericPortionOfAddress(address);


            if (endingIndex == 0)
                return address;


            int originalNumber;


            Int32.TryParse(address.Substring(0, endingIndex + 1), out originalNumber);


            if (originalNumber == 0)
                return address;


            var roundedNumber = originalNumber.RoundToLowestHundreds();


            return address.Replace(originalNumber.ToString(), roundedNumber.ToString());
        }


        // finds the last position index of the street address number
        static int GetEndingIndexOfNumericPortionOfAddress(string address)
        {
            int endingIndex = 0;


            for (int i = 0; i < address.Length; i++)
            {
                if (Char.IsDigit(address[i]))
                    endingIndex = i;
                else
                    break;
            }


            return endingIndex;
        }
    }
}

 
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