Can't bind

Location.xaml

<?xml version="1.0" encoding="UTF-8"?>

<ContentView xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:controls="clr-namespace:Naxam.Controls.Mapbox.Forms;assembly=Naxam.Mapbox.Forms"
             xmlns:forms="clr-namespace:FFImageLoading.Forms;assembly=FFImageLoading.Forms"
             xmlns:controls1="clr-namespace:DLToolkit.Forms.Controls;assembly=DLToolkit.Forms.Controls.FlowListView"
             x:Class="Via.Views.Location">
    <ContentView.Content>
        <AbsoluteLayout>
            <ScrollView VerticalScrollBarVisibility="Never" Padding="15,8,15,8" AbsoluteLayout.LayoutBounds="0,0,1,1"
                    <StackLayout Orientation="Vertical">
                        <StackLayout Orientation="Vertical" BackgroundColor="Black">
                            <Button
                                Text="Take a Photo or Select from Library"
                                BackgroundColor="#00314B"
                                HorizontalOptions="FillAndExpand"
                                TextColor="White"
                                Clicked="Button_OnClicked"
                                CornerRadius="3" />
                            <controls1:FlowListView FlowColumnCount="3" x:Name="listItems" FlowItemsSource="{Binding Media}"
                                              SeparatorVisibility="None"
                                              HasUnevenRows="false" RowHeight="100" >
                                <controls1:FlowListView.FlowColumnTemplate>
                                    <DataTemplate >
                                        <Grid>
                                            <forms:CachedImage  DownsampleToViewSize="true" HeightRequest="100"  Source="{Binding PreviewPath}"  Aspect="AspectFill" HorizontalOptions="FillAndExpand">
                                            </forms:CachedImage>
                                            <Image Source="play" IsVisible="false" HorizontalOptions="End" VerticalOptions="End">
                                                <Image.Triggers>
                                                    <DataTrigger TargetType="Image" Binding="{Binding Type}" Value="Video">
                                                        <Setter Property="IsVisible" Value="True" />
                                                    </DataTrigger>
                                                </Image.Triggers>
                                            </Image>
                                        </Grid>
                                    </DataTemplate>
                                </controls1:FlowListView.FlowColumnTemplate>
                            </controls1:FlowListView>
                        </StackLayout>
                    </StackLayout>
                </StackLayout>
            </ScrollView>        
        </AbsoluteLayout>
    </ContentView.Content>
</ContentView>

Location.xaml.cs

using System;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Net.Http;
using System.Threading.Tasks;
using DLToolkit.Forms.Controls;
using Naxam.Controls.Mapbox.Forms;
using Newtonsoft.Json;
using Plugin.Permissions;
using Plugin.Permissions.Abstractions;
using Via.Helpers;
using Via.Models;
using Via.Services;
using Via.utils;
using Via.ViewModels;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
using static Via.Models.Accident;

namespace Via.Views
{
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class Location : ContentView
    {
    
        public Location()
        {
            InitializeComponent();
      
            BindingContext = new MainViewModel(DependencyService.Get<IMultiMediaPickerService>());
            
        }
      
      
    }
}

MainActivity.cs

using System;
using Android.App;
using Android.Content;
using Android.Content.PM;
using Android.OS;
using Android.Runtime;
using Android.Support.V4.Content;
using Android.Views;
using Android.Widget;
using Com.Mapbox.Mapboxsdk;
using Com.Mapbox.Mapboxsdk.Annotations;
using Com.Mapbox.Mapboxsdk.Geometry;
using Com.Mapbox.Mapboxsdk.Maps;
using FFImageLoading.Forms.Platform;
using Plugin.InputKit.Platforms.Droid;
using Plugin.Permissions;
using Via.Droid.Services;
using Via.Helpers;
using Via.utils;
using Via.ViewModels;
using Via.Views;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
using static Com.Mapbox.Mapboxsdk.Maps.MapboxMap;
using Color = Android.Graphics.Color;
using Object = Java.Lang.Object;
using View = Android.Views.View;

namespace Via.Droid
{
    [Activity(Label = "Via", Icon = "@mipmap/icon", Theme = "@style/MainTheme", MainLauncher = true,
        ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
    public class MainActivity : FormsAppCompatActivity
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            TabLayoutResource = Resource.Layout.Tabbar;
            ToolbarResource = Resource.Layout.Toolbar;

            base.OnCreate(savedInstanceState);

            CachedImageRenderer.Init(true);

            Config.Init(this, savedInstanceState);

            global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
            LoadApplication(new App());

            new GetMultimedia(MultiMediaPickerService.SharedInstance);

            //Initialize mapbox in Android.
            Mapbox.GetInstance(this, MapBoxService.AccessToken);
        }

        
    }
}

MainViewModel.cs

using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Input;
using Plugin.Permissions;
using Plugin.Permissions.Abstractions;
using Via.Helpers;
using Via.Models;
using Via.Services;
using Xamarin.Forms;

namespace Via.ViewModels
{
     public class MainViewModel : INotifyPropertyChanged
    {
        IMultiMediaPickerService _multiMediaPickerService;

        public ObservableCollection<MediaFile> Media { get; set; }
        public ICommand SelectImagesCommand { get; set; }
        public ICommand SelectVideosCommand { get; set; }

        public MainViewModel(IMultiMediaPickerService multiMediaPickerService)
        {
            _multiMediaPickerService = multiMediaPickerService;
            SelectImagesCommand = new Command(async (obj) =>
            {
                var hasPermission = await CheckPermissionsAsync();
                if (hasPermission)
                {
                    Media = new ObservableCollection<MediaFile>();
                    await _multiMediaPickerService.PickPhotosAsync();
                }
            });

            SelectVideosCommand = new Command(async (obj) =>
            {
                var hasPermission = await CheckPermissionsAsync();
                if (hasPermission)
                {

                    Media = new ObservableCollection<MediaFile>();

                    await _multiMediaPickerService.PickVideosAsync();

                }
            });

            _multiMediaPickerService.OnMediaPicked += (s, a) =>
            {
                Device.BeginInvokeOnMainThread(() =>
                {
                    Media.Add(a);

                });
               
            };
        }

        async Task<bool> CheckPermissionsAsync()
        {
            var retVal = false;
            try
            {
                var status = await CrossPermissions.Current.CheckPermissionStatusAsync(Plugin.Permissions.Abstractions.Permission.Storage);
                if (status != PermissionStatus.Granted)
                {
                    if (await CrossPermissions.Current.ShouldShowRequestPermissionRationaleAsync(Plugin.Permissions.Abstractions.Permission.Storage))
                    {
                        await App.Current.MainPage.DisplayAlert("Alert","Need Storage permission to access to your photos.","Ok");
                    }

                    var results = await CrossPermissions.Current.RequestPermissionsAsync(new[] { Plugin.Permissions.Abstractions.Permission.Storage });
                    status = results[Plugin.Permissions.Abstractions.Permission.Storage];
                }

                if (status == PermissionStatus.Granted)
                {
                    retVal = true;

                }
                else if (status != PermissionStatus.Unknown)
                {
                    await App.Current.MainPage.DisplayAlert("Alert","Permission Denied. Can not continue, try again.","Ok");
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
                await App.Current.MainPage.DisplayAlert("Alert", "Error. Can not continue, try again.", "Ok");
            }

            return retVal;

        }
        public event PropertyChangedEventHandler PropertyChanged;
    }
}