location adjustment

Billing.Shared/Views/AddBillPage.xaml

@@ -10,6 +10,7 @@
                 BindingContext="{x:Reference billPage}">
 
     <ContentPage.ToolbarItems>
+        <ToolbarItem Order="Primary" IconImageSource="pin.png" Command="{Binding ViewLocation}"/>
         <ToolbarItem Order="Primary" IconImageSource="check.png" Command="{Binding CheckBill}"/>
     </ContentPage.ToolbarItems>
 
@@ -49,9 +50,6 @@
                 <ui:OptionEntryCell Height="44" Icon="online.png"
                                     Title="{r:Text Store}"
                                     Text="{Binding Store, Mode=TwoWay}"/>
-                <ui:OptionSelectCell Height="44"
-                                     Detail="{r:Text ViewLocation}"
-                                     Command="{Binding ViewLocation}"/>
                 <ui:OptionDatePickerCell Height="44" Icon="bars.png"
                                          Title="{r:Text CreatedTime}"
                                          Date="{Binding CreatedDate, Mode=TwoWay}"/>

Billing.Shared/Views/AddBillPage.xaml.cs

@@ -316,6 +316,7 @@ namespace Billing.Views
                     Longitude = location.Longitude,
                     Latitude = location.Latitude
                 });
+                page.Synced += (sender, loc) => location = loc;
                 await Navigation.PushAsync(page);
             }
         }

Billing.Shared/Views/ViewLocationPage.cs

@@ -1,17 +1,37 @@
-using Billing.Models;
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Billing.Models;
 using Billing.UI;
+using Xamarin.Essentials;
+using Xamarin.Forms;
 using Xamarin.Forms.Maps;
 using Xamarin.Forms.PlatformConfiguration.iOSSpecific;
+using Map = Xamarin.Forms.Maps.Map;
 
 namespace Billing.Views
 {
     public class ViewLocationPage : BillingPage
     {
+        public event EventHandler<Location> Synced;
+
+        private readonly Bill bill;
+
+        private CancellationTokenSource tokenSource;
+
         public ViewLocationPage(Bill bill)
         {
             On<Xamarin.Forms.PlatformConfiguration.iOS>().SetUseSafeArea(false);
+            this.bill = bill;
             Title = bill.Name;
 
+            ToolbarItems.Add(new ToolbarItem
+            {
+                IconImageSource = "location.png",
+                Order = ToolbarItemOrder.Primary,
+                Command = new Command(OnSynced)
+            });
+
             if (bill.Latitude != null && bill.Longitude != null)
             {
                 var (longitude, latitude) = (bill.Longitude.Value, bill.Latitude.Value).Wgs84ToGcj02();
@@ -32,5 +52,78 @@ namespace Billing.Views
                 };
             }
         }
+
+        protected override void OnDisappearing()
+        {
+            if (tokenSource != null && !tokenSource.IsCancellationRequested)
+            {
+                tokenSource.Cancel();
+            }
+            base.OnDisappearing();
+        }
+
+        private async void OnSynced()
+        {
+            if (Tap.IsBusy)
+            {
+                return;
+            }
+            using (Tap.Start())
+            {
+                if (tokenSource != null)
+                {
+                    return;
+                }
+                var location = await GetCurrentLocation();
+                if (location != null)
+                {
+                    Synced?.Invoke(this, location);
+
+                    MainThread.BeginInvokeOnMainThread(() =>
+                    {
+                        var (longitude, latitude) = (location.Longitude, location.Latitude).Wgs84ToGcj02();
+                        var position = new Position(latitude, longitude);
+                        var mapSpan = new MapSpan(position, 0.01, 0.01);
+                        Content = new Map(mapSpan)
+                        {
+                            Pins =
+                            {
+                                new Pin
+                                {
+                                    Label = bill.Name,
+                                    Type = PinType.Generic,
+                                    Position = position,
+                                    Address = bill.Store
+                                }
+                            }
+                        };
+                    });
+                }
+            }
+        }
+
+        private async Task<Location> GetCurrentLocation()
+        {
+            try
+            {
+                var request = new GeolocationRequest(GeolocationAccuracy.Best, TimeSpan.FromSeconds(10));
+                tokenSource = new CancellationTokenSource();
+                var status = await Helper.CheckAndRequestPermissionAsync<Permissions.LocationWhenInUse>();
+                if (status != PermissionStatus.Granted)
+                {
+                    return null;
+                }
+                return await Geolocation.GetLocationAsync(request, tokenSource.Token);
+            }
+            catch (FeatureNotSupportedException) { }
+            catch (FeatureNotEnabledException) { }
+            catch (PermissionException) { }
+            catch (Exception ex)
+            {
+                Helper.Error("location.get", ex);
+            }
+            tokenSource = null;
+            return null;
+        }
     }
 }