Added ability to swipe between views with setting context by user

No need to set Items Context

PanCardView/CardsView.cs

@@ -44,6 +44,17 @@ public class CardsView : AbsoluteLayout
             bindable.AsCardView().SetCurrentView();
         });
 
+        public static readonly BindableProperty CurrentContextProperty = BindableProperty.Create(nameof(CurrentContext), typeof(object), typeof(CardsView), null, BindingMode.OneWay, propertyChanged: (bindable, oldValue, newValue) => {
+            if(newValue != null && bindable.AsCardView()._currentView == null)
+            {
+                bindable.AsCardView().SetCurrentView();
+            }
+        });
+
+        public static readonly BindableProperty NextContextProperty = BindableProperty.Create(nameof(NextContext), typeof(object), typeof(CardsView), null, BindingMode.OneWay);
+
+        public static readonly BindableProperty PrevContextProperty = BindableProperty.Create(nameof(PrevContext), typeof(object), typeof(CardsView), null, BindingMode.OneWay);
+
         public static readonly BindableProperty MoveDistanceProperty = BindableProperty.Create(nameof(MoveDistance), typeof(double), typeof(CardsView), -1.0);
 
         public static readonly BindableProperty IsOnlyForwardDirectionProperty = BindableProperty.Create(nameof(IsOnlyForwardDirection), typeof(bool), typeof(CardsView), false);
@@ -56,7 +67,7 @@ public class CardsView : AbsoluteLayout
 
         public static readonly BindableProperty MaxChildrenCountProperty = BindableProperty.Create(nameof(MaxChildrenCount), typeof(int), typeof(CardsView), 18);
 
-        public static readonly BindableProperty DesiredMaxChildrenCountProperty = BindableProperty.Create(nameof(DesiredMaxChildrenCount), typeof(int), typeof(CardsView), 12);
+        public static readonly BindableProperty DesiredMaxChildrenCountProperty = BindableProperty.Create(nameof(DesiredMaxChildrenCount), typeof(int), typeof(CardsView), 9);
 
         public static readonly BindableProperty PanStartedCommandProperty = BindableProperty.Create(nameof(PanStartedCommand), typeof(ICommand), typeof(CardsView), null);
 
@@ -132,6 +143,24 @@ public CardViewItemFactory ItemViewFactory
             set => SetValue(ItemViewFactoryProperty, value);
         }
 
+        public object CurrentContext
+        {
+            get => GetValue(CurrentContextProperty);
+            set => SetValue(CurrentContextProperty, value);
+        }
+
+        public object NextContext
+        {
+            get => GetValue(NextContextProperty);
+            set => SetValue(NextContextProperty, value);
+        }
+
+        public object PrevContext
+        {
+            get => GetValue(PrevContextProperty);
+            set => SetValue(PrevContextProperty, value);
+        }
+
         public double MoveDistance
         {
             get
@@ -206,7 +235,7 @@ public ICommand PositionChangedCommand
 
         public void OnPanUpdated(object sender, PanUpdatedEventArgs e)
         {
-            if (_itemsCount < 0)
+            if (_itemsCount < 0 && CurrentContext == null)
             {
                 return;
             }
@@ -234,7 +263,7 @@ public void OnPanUpdated(object sender, PanUpdatedEventArgs e)
 
         private void SetCurrentView()
         {
-            if (Items != null && CurrentIndex < _itemsCount)
+            if ((Items != null && CurrentIndex < _itemsCount) || CurrentContext  != null)
             {
                 _currentView = GetView(CurrentIndex, PanItemPosition.Current);
             }
@@ -312,27 +341,16 @@ private async void OnTouchEnded()
 
             if (absDiff > MoveDistance)
             {
-                var indexDelta = -Math.Sign(CurrentDiff);
-                if (IsOnlyForwardDirection)
+                var index = GetNewIndexFromDiff();
+                if(index < 0)
                 {
-                    indexDelta = Math.Abs(indexDelta);
-                }
-                var newIndex = CurrentIndex + indexDelta;
-
-                if (newIndex < 0 || newIndex >= _itemsCount)
-                {
-                    if (!IsRecycled)
-                    {
-                        return;
-                    }
-
-                    newIndex = GetRecycledIndex(newIndex);
+                    return;
                 }
 
                 SwapViews();
                 ShouldIgnoreSetCurrentView = true;
 
-                CurrentIndex = newIndex;
+                CurrentIndex = index;
 
                 FirePanEnded(CurrentDiff < 0);
 
@@ -376,6 +394,33 @@ await Task.WhenAll(
             }
         }
 
+        private int GetNewIndexFromDiff()
+        {
+            if(CurrentContext != null)
+            {
+                return 0;
+            }
+
+            var indexDelta = -Math.Sign(CurrentDiff);
+            if (IsOnlyForwardDirection)
+            {
+                indexDelta = Math.Abs(indexDelta);
+            }
+            var newIndex = CurrentIndex + indexDelta;
+
+            if (newIndex < 0 || newIndex >= _itemsCount)
+            {
+                if (!IsRecycled)
+                {
+                    return - 1;
+                }
+
+                newIndex = GetRecycledIndex(newIndex);
+            }
+
+            return newIndex;
+        }
+
         private bool TrySetSelectedBackView(double diff)
         {
             View invisibleView;
@@ -423,23 +468,11 @@ private void SwapViews()
 
         private View GetView(int index, PanItemPosition panIntemPosition)
         {
-            if(_itemsCount < 0)
+            var context = GetContext(index, panIntemPosition);
+            if(context == null)
             {
                 return null;
             }
-
-            if(index < 0 || index >= _itemsCount)
-            {
-                if(!IsRecycled || (panIntemPosition != PanItemPosition.Current && _itemsCount < 2))
-                {
-                    return null;
-                }
-
-                index = GetRecycledIndex(index);
-
-            }
-
-            var context = Items[index];
 
             var rule = ItemViewFactory?.GetRule(context);
             if(rule == null)
@@ -478,6 +511,39 @@ private View GetView(int index, PanItemPosition panIntemPosition)
             return view;
         }
 
+        private object GetContext(int index, PanItemPosition panIntemPosition)
+        {
+            if (CurrentContext != null)
+            {
+                switch (panIntemPosition)
+                {
+                    case PanItemPosition.Current:
+                        return CurrentContext;
+                    case PanItemPosition.Next:
+                        return NextContext;
+                    case PanItemPosition.Prev:
+                        return PrevContext;
+                }
+            }
+
+            if (_itemsCount < 0)
+            {
+                return null;
+            }
+
+            if (index < 0 || index >= _itemsCount)
+            {
+                if (!IsRecycled || (panIntemPosition != PanItemPosition.Current && _itemsCount < 2))
+                {
+                    return null;
+                }
+
+                index = GetRecycledIndex(index);
+            }
+
+            return Items[index];
+        }
+
         private void SetBackViewLayerPosition(View view)
         {
             if(view == null)

PanCardView/Factory/CardViewFactoryRule.cs

@@ -5,6 +5,15 @@ namespace PanCardView.Factory
 {
     public sealed class CardViewFactoryRule
     {
+        public CardViewFactoryRule()
+        {
+        }
+
+        public CardViewFactoryRule(Func<View> creator)
+        {
+            Creator = creator;
+        }
+
         public Func<View> Creator { get; set; }
     }
 }

PanCardViewSample/PanCardViewSample/PanCardViewSample.cs

@@ -15,11 +15,16 @@ public class StartPage : ContentPage
     {
         public StartPage()
         {
-            var toCardsBtn = new Button { Text = "CardsView" };
+            var toCardsBtn = new Button { Text = "CardsView Items" };
             toCardsBtn.Clicked += (sender, e) => {
                 this.Navigation.PushAsync(new CardsSampleView());
             };
 
+            var toCardsBtnCustom = new Button { Text = "CardsView CustomContexts" };
+            toCardsBtnCustom.Clicked += (sender, e) => {
+                this.Navigation.PushAsync(new CardsSampleCustomView());
+            };
+
             var toCarouselBtn = new Button { Text = "CarouselView" };
             toCarouselBtn.Clicked += (sender, e) => {
                 this.Navigation.PushAsync(new CarouselSampleView());
@@ -29,6 +34,7 @@ public StartPage()
             {
                 Children = {
                     toCardsBtn,
+                    toCardsBtnCustom,
                     toCarouselBtn
                 }
             };

PanCardViewSample/PanCardViewSample/PanCardViewSample.csproj

@@ -34,6 +34,8 @@
     <Compile Include="Views\CarouselSampleView.cs" />
     <Compile Include="ViewModels\CardSampleViewModel.cs" />
     <Compile Include="CardsFactory\RuleHolder.cs" />
+    <Compile Include="Views\CardsSampleCustomView.cs" />
+    <Compile Include="ViewModels\SharedSampleCustomViewModel.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\PanCardView\PanCardView.csproj">

PanCardViewSample/PanCardViewSample/ViewModels/SharedSampleCustomViewModel.cs

@@ -0,0 +1,90 @@
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using Xamarin.Forms;
+using System;
+using System.Collections.Generic;
+using System.Windows.Input;
+using System.Linq;
+
+namespace PanCardViewSample.ViewModels
+{
+    public sealed class SharedSampleCustomViewModel : INotifyPropertyChanged
+    {
+        public event PropertyChangedEventHandler PropertyChanged;
+
+        private int _ImageCount = 500;
+
+        private Stack<object> _contextStack = new Stack<object>();
+
+        public SharedSampleCustomViewModel()
+        {
+            PrevContext = CreateContext();
+            CurrentContext = CreateContext();
+            NextContext = CreateContext();
+
+            _contextStack.Push(PrevContext);
+
+            PanStartedCommand = new Command(() =>
+            {
+                if (_contextStack.Any() && PrevContext == null)
+                {
+                    PrevContext = _contextStack.Peek();
+                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(PrevContext)));
+                }
+                if (NextContext == null)
+                {
+                    NextContext = new { Source = CreateSource(), Color = CreateColor() };
+                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(NextContext)));
+                }
+
+            });
+
+            PanPositionChangedCommand = new Command((p) =>
+            {
+                var isNext = (bool)p;
+                if(isNext)
+                {
+                    _contextStack.Push(CurrentContext);
+                    PrevContext = CurrentContext;
+                    CurrentContext = NextContext;
+                    NextContext = CreateContext();
+                }
+                else
+                {
+                    NextContext = CurrentContext;
+                    CurrentContext = PrevContext;
+                    _contextStack.Pop();
+                    PrevContext = _contextStack.Any() ? _contextStack.Peek() : null;
+                }
+
+                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(CurrentContext)));
+                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(NextContext)));
+                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(PrevContext)));
+            });
+        }
+
+        public object CurrentContext { get; set; }
+        public object NextContext { get; set; }
+        public object PrevContext { get; set; }
+
+        public ICommand PanStartedCommand { get; } 
+        public ICommand PanPositionChangedCommand { get; } 
+
+
+        private object CreateContext()
+        {
+            return new { Source = CreateSource(), Color = CreateColor() };
+        }
+
+        private string CreateSource()
+        {
+            return $"http://lorempixel.com/300/300/animals/text{++_ImageCount}/";
+        }
+
+        private Color CreateColor()
+        {
+            var rnd = new Random();
+            return Color.FromRgb(rnd.Next(0, 255), rnd.Next(0, 255), rnd.Next(0, 255));
+        }
+    }
+}

PanCardViewSample/PanCardViewSample/Views/CardsSampleCustomView.cs

@@ -0,0 +1,34 @@
+using FFImageLoading.Forms;
+using PanCardView;
+using PanCardView.Factory;
+using Xamarin.Forms;
+using PanCardView.Processors;
+using PanCardViewSample.ViewModels;
+using PanCardViewSample.CardsFactory;
+
+namespace PanCardViewSample.Views
+{
+    public class CardsSampleCustomView : ContentPage
+    {
+        public CardsSampleCustomView()
+        {
+            var cardsView = new CardsView()
+            {
+                ItemViewFactory = new CardViewItemFactory(RuleHolder.Rule),
+                BackgroundColor = Color.Black.MultiplyAlpha(.9),
+                IsPanInCourse = true
+            };
+
+            cardsView.SetBinding(CardsView.CurrentContextProperty, nameof(SharedSampleCustomViewModel.CurrentContext));
+            cardsView.SetBinding(CardsView.NextContextProperty, nameof(SharedSampleCustomViewModel.NextContext));
+            cardsView.SetBinding(CardsView.PrevContextProperty, nameof(SharedSampleCustomViewModel.PrevContext));
+
+            cardsView.SetBinding(CardsView.PanStartedCommandProperty, nameof(SharedSampleCustomViewModel.PanStartedCommand));
+            cardsView.SetBinding(CardsView.PositionChangedCommandProperty, nameof(SharedSampleCustomViewModel.PanPositionChangedCommand));
+
+            Title = "CardsView";
+            Content = cardsView;
+            BindingContext = new SharedSampleCustomViewModel();
+        }
+    }
+}