Sheet fling fixes (#298)

* Seems to work

* Android, top and bottom alignment

* Adjustments

* Deleted cheat sheet

* Removed position changed command and event

* Added MoveTo()

* Commands and Events are invoked.

* Removed Alignment

* Refactor

* iOS fixes

* Refactor

* Added overlay

* Added comments

* Update SheetView.xaml.cs

* Sheet can be pinned if snap points are configured correctly

* IgnoreLocalTime in tests

* Overlay attempt

* Open sheet on scrollable content iOS

* Updated/deleted issue repro

* Added bindable property for intercepting drag gestures on content

* Updated doc

* Better algorithm for finding index of closest snap point

* Update DIPS.Xamarin.UI.Tests.csproj

* Delete PositionEventArgs.cs

* Changed default colors

* Changed sheet title default color

* Added PanAwareContentView to iOS

* Add IsBusy to sheet

* Fixed busy view not appearing

* Removed busy view frame shadow

* Intercept scroll draft iOS

* Toggle scrollable content

* File renamings, langauge version bumps

* Removed OverlayBoxView

* Update SheetContentView.cs

* Android scroll interception

* Made Handle change opacity instead of visibility

* Add slight overshoot to animation and adjusted fling

* Disable drag when translating

* MoveTo() animates change

* Don‘t move sheet if it’s in the correct position already

* Fixed fling bugs

* Removed console.writelines

Co-authored-by: Erling Moxnes Kristiansen <emk@dips.no>

src/DIPS.Xamarin.UI.Android/SheetContentView.cs

@@ -89,12 +89,10 @@ public override void RequestDisallowInterceptTouchEvent(bool disallowIntercept)
         {
             base.RequestDisallowInterceptTouchEvent(disallowIntercept);
             m_interceptDisallowed = disallowIntercept;
-            Console.WriteLine($"DISALLOW INTERCEPT: {disallowIntercept}");
         }
 
         public override bool OnInterceptTouchEvent(MotionEvent ev)
         {
-            Console.WriteLine($"INTERCEPTING TOUCH EVENT {ev.ActionMasked}");
             switch (ev.ActionMasked)
             {
                 case MotionEventActions.Cancel:
@@ -130,7 +128,6 @@ public override bool OnInterceptTouchEvent(MotionEvent ev)
 
         public override bool OnTouchEvent(MotionEvent e)
         {
-            Console.WriteLine($"TOUCH EVENT {e.ActionMasked}");
             var (x, y) = ToDip(e.RawX, e.RawY);
 
             if (e.ActionMasked is MotionEventActions.Up or MotionEventActions.Cancel) // ended gesture

src/DIPS.Xamarin.UI/Controls/Sheet/FlingSensitivity.cs

@@ -6,18 +6,25 @@
     public enum FlingSensitivity
     {
         /// <summary>
-        /// 2500 pixels per second
+        /// 3500 pixels per second
         /// </summary>
         Low,
 
         /// <summary>
-        /// 1250 pixels per second
+        /// 2000 pixels per second
         /// </summary>
         Medium,
 
         /// <summary>
-        /// 500 pixels per second
+        /// 1000 pixels per second
         /// </summary>
         High
     }
+
+    internal static class FlingConstants
+    {
+        internal static int s_low = 3500;
+        internal static int s_medium = 2000;
+        internal static int s_high = 1000;
+    }
 }

src/DIPS.Xamarin.UI/Controls/Sheet/FlingSensitivityConverter.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Globalization;
-using DIPS.Xamarin.UI.Internal.Xaml.Sheet;
 using Xamarin.Forms;
 using Xamarin.Forms.Xaml;
 
@@ -37,17 +36,17 @@ public override object ConvertFromInvariantString(string value)
                 switch (result)
                 {
                     case FlingSensitivity.Low:
-                        return 2500;
+                        return FlingConstants.s_low;
                     case FlingSensitivity.Medium:
-                        return 1250;
+                        return FlingConstants.s_medium;
                     case FlingSensitivity.High:
-                        return 500;
+                        return FlingConstants.s_high;
                     default:
                         throw new ArgumentOutOfRangeException();
                 }
             }
-
-            return 1250;
+            
+            return FlingConstants.s_medium;
         }
     }
 }

src/DIPS.Xamarin.UI/Controls/Sheet/SheetBehaviorProps.cs

@@ -345,7 +345,7 @@ public partial class SheetBehavior
         ///     <see cref="FlingSpeedThreshold" />
         /// </summary>
         public static readonly BindableProperty FlingSpeedThresholdProperty =
-            BindableProperty.Create(nameof(FlingSpeedThreshold), typeof(int), typeof(SheetBehavior), 1250);
+            BindableProperty.Create(nameof(FlingSpeedThreshold), typeof(int), typeof(SheetBehavior), FlingConstants.s_medium );
 
         /// <summary>
         ///     <see cref="SheetOpeningStrategy" />
@@ -390,7 +390,7 @@ public double TitleSize
         ///     This is a bindable property.
         /// </summary>
         /// <remarks>
-        ///     Default value is 1250. Unit is pixels per second. Pre-defined values are <see cref="FlingSensitivity.Low" />,
+        ///     Default value is 2000 . Unit is pixels per second. Pre-defined values are <see cref="FlingSensitivity.Low" />,
         ///     <see cref="FlingSensitivity.Medium" /> and <see cref="FlingSensitivity.High" />
         /// </remarks>
         [TypeConverter(typeof(FlingSensitivityConverter))]

src/DIPS.Xamarin.UI/Internal/Xaml/Sheet/SheetView.xaml.cs

@@ -93,12 +93,15 @@ public void SendPan(float totalX, float totalY, float distanceX, float distanceY
                     OnDragStarted();
                     break;
                 case GestureStatus.Running:
-                    if (m_isTranslating) return;
+                    if (m_isTranslating)
+                    {
+                        this.CancelAnimations();
+                    }
+
                     MoveSheet(distanceY);
                     RecordDelta(distanceY);
                     break;
                 case GestureStatus.Completed:
-                    MoveSheet(distanceY);
                     OnDragEnded();
                     break;
                 case GestureStatus.Canceled:
@@ -178,7 +181,7 @@ private async Task Minimize(float velocity = 1500)
 
         internal Task Close()
         {
-            return TranslateSheetTo(m_sheetBehaviour.Alignment == AlignmentOptions.Bottom ? Height : -Height, 1750);
+            return TranslateSheetTo(m_sheetBehaviour.Alignment == AlignmentOptions.Bottom ? Height : -Height);
         }
 
         private void SetState(SheetState state)
@@ -231,20 +234,24 @@ internal async Task Open()
 
         private void OnDragStarted()
         {
+            m_prevDuration = 0;
             m_watch = Stopwatch.StartNew();
         }
 
-        private void OnDragEnded()
+        private async Task OnDragEnded()
         {
             m_watch.Stop();
 
             var direction = SheetViewUtility.FindLatestDragDirection(ref m_latestDeltas);
-
-            if (TryFling(direction, out var velocity)) { }
-            else
+
+            var (didFling, velocity) = await TryFling(direction);
+
+            if (didFling)
             {
-                SnapTo(direction, velocity);
+                return;
             }
+
+            await SnapTo(direction, velocity);
         }
 
         private async Task SnapTo(DragDirection dragDirection, float velocity)
@@ -282,6 +289,7 @@ private async Task TranslateSheetTo(double y, float velocity = 1500)
 
             duration = duration > 250 ? 250 : duration < 200 ? 200 : duration;
 
+            this.CancelAnimations();
             await this.TranslateTo(0, y + (dir ? 5 : -5), (uint)duration, Easing.CubicOut);
             await this.TranslateTo(0, y, 225, Easing.CubicOut);
 
@@ -299,32 +307,28 @@ private void NotifyPositionChange()
             m_sheetBehaviour.Position = 1 - this.YValueToRatio(TranslationY);
         }
 
-        private bool TryFling(DragDirection dragDirection, out float velocity)
+        private async Task<(bool, float)> TryFling(DragDirection dragDirection)
         {
             var (thresholdReached, v) = SheetViewUtility.IsThresholdReached(ref m_latestDeltas, PixelsPerSecond);
 
-            velocity = v;
-
             if (thresholdReached)
             {
                 switch (dragDirection)
                 {
                     case DragDirection.Up when m_sheetBehaviour.Alignment == AlignmentOptions.Bottom:
                     case DragDirection.Down when m_sheetBehaviour.Alignment == AlignmentOptions.Top:
-                        Maximize(v);
-                        break;
+                        await Maximize(v);
+                        return (true, v);
                     case DragDirection.Down when m_sheetBehaviour.Alignment == AlignmentOptions.Bottom:
                     case DragDirection.Up when m_sheetBehaviour.Alignment == AlignmentOptions.Top:
-                        Minimize(v);
-                        break;
+                        await Minimize(v);
+                        return (true, v);
                     default:
                         throw new ArgumentOutOfRangeException(nameof(dragDirection), dragDirection, null);
                 }
-
-                return true;
             }
 
-            return false;
+            return (false, v);
         }
 
         internal void Initialize()

src/DIPS.Xamarin.UI/Internal/Xaml/Sheet/SheetViewUtility.cs

@@ -20,8 +20,8 @@ internal static (bool, float) IsThresholdReached(ref (float, long)[] latestDelta
             latestDeltas = new (float, long)[latestDeltas.Length];
 
             var velocity = Math.Abs(length) / duration * 1000;
-            
-            if (length < 25) return (false, velocity); // must always travel more than this 
+
+            if (duration < 60) return (false, velocity); // must always travel more than this 
 
             return (velocity >= threshold, velocity);
         }