Added DrawingOptions

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

@@ -20,8 +20,7 @@ public class SheetBehavior : Behavior<ModalityLayout>, IModalityHandler
         private ModalityLayout? m_modalityLayout;
 
         private SheetView? m_sheetView;
-        public event EventHandler? OnOpen;
-        public event EventHandler? OnClose;
+
         /// <summary>
         /// <see cref="OnOpenCommand"/>
         /// </summary>
@@ -166,7 +165,22 @@ public class SheetBehavior : Behavior<ModalityLayout>, IModalityHandler
             typeof(SheetBehavior),
             ColorPalette.QuinaryAir);
 
+        /// <summary>
+        /// <see cref="DrawOptions"/>
+        /// </summary>
+        public static readonly BindableProperty DrawOptionsProperty = BindableProperty.Create(nameof(DrawOptions), typeof(SheetContentDrawOptions), typeof(SheetBehavior));
+
+        /// <summary>
+        /// Determines when the sheet content should be drawn on the screen.
+        /// </summary>
+        public SheetContentDrawOptions DrawOptions
+        {
+            get => (SheetContentDrawOptions)GetValue(DrawOptionsProperty);
+            set => SetValue(DrawOptionsProperty, value);
+        }
+
         private bool m_fromIsDraggingContext;
+        private bool m_isLazyLoadingView;
 
         /// <summary>
         ///     Determines the position of the sheet when it appears.
@@ -240,7 +254,12 @@ public bool IsOpen
         }
 
         /// <summary>
-        /// Command that executes when the sheet has completed it's animation and is open
+        /// Event that gets raised when the sheet has completed it's animation and is open
+        /// </summary>
+        public event EventHandler? OnOpen;
+
+        /// <summary>
+        /// Command that executes when the sheet has completed it's animation and is open.
         /// </summary>
         public ICommand OnOpenCommand
         {
@@ -249,7 +268,7 @@ public ICommand OnOpenCommand
         }
 
         /// <summary>
-        /// The parameter to pass to the <see cref="OnOpenCommand"/>
+        /// The parameter to pass to the <see cref="OnOpenCommand"/>.
         /// </summary>
         public object OnOpenCommandParameter
         {
@@ -258,7 +277,12 @@ public object OnOpenCommandParameter
         }
 
         /// <summary>
-        /// Command that executes when the sheet has completed it's animation and is closed
+        /// Event that gets raised when the sheet has completed it's animation and is closed
+        /// </summary>
+        public event EventHandler? OnClose;
+
+        /// <summary>
+        /// Command that executes when the sheet has completed it's animation and is closed.
         /// </summary>
         public ICommand OnCloseCommand
         {
@@ -267,7 +291,7 @@ public ICommand OnCloseCommand
         }
 
         /// <summary>
-        /// The parameter to pass to the <see cref="OnCloseCommand"/>
+        /// The parameter to pass to the <see cref="OnCloseCommand"/>.
         /// </summary>
         public object OnCloseCommandParameter
         {
@@ -394,9 +418,17 @@ private async void ToggleSheetVisibility()
                 return;
             }
 
+            m_isLazyLoadingView = true;
+
             if (IsOpen)
             {
                 m_sheetView = new SheetView(this);
+
+                if (DrawOptions == SheetContentDrawOptions.BeforeOpen)
+                {
+                    m_sheetView.SheetContentView.Content = SheetContent;
+                }
+
                 m_sheetView.Initialize();
                 SheetContent.BindingContext = BindingContextFactory?.Invoke() ?? BindingContext;
 
@@ -416,19 +448,30 @@ private async void ToggleSheetVisibility()
                     _ => throw new ArgumentOutOfRangeException()
                 };
 
-
                 //Set position based on size of content
                 if (Position <= 0)
                 {
-                    //Calculate what size the content needs if the position is set to 0
-                    Position = m_sheetView.SheetContentHeighRequest / m_modalityLayout.Height;
+                    if (DrawOptions == SheetContentDrawOptions.OnOpen)
+                    {
+                        Position = MinPosition;
+                    }
+                    else
+                    {
+                        //Calculate what size the content needs if the position is set to 0
+                        Position = m_sheetView.SheetContentHeightRequest / m_modalityLayout.Height;
+                    }
                 }
                 else //Set position from input
                 {
                     await TranslateBasedOnPosition(false);
                     OnOpenCommand?.Execute(OnOpenCommandParameter);
                     OnOpen?.Invoke(this, new EventArgs());
                 }
+
+                if (DrawOptions == SheetContentDrawOptions.OnOpen)
+                {
+                    m_sheetView.SheetContentView.Content = SheetContent;
+                }
             }
             else
             {
@@ -552,4 +595,19 @@ public enum ContentAlignment
         /// </summary>
         Fill
     }
+
+    /// <summary>
+    /// The sheet content draw options
+    /// </summary>
+    public enum SheetContentDrawOptions
+    {
+        /// <summary>
+        /// Draw the sheet content before the sheet is open, this happens the moment the sheet starts to open
+        /// </summary>
+        BeforeOpen = 0,
+        /// <summary>
+        /// Draw the sheet content when the sheet is open, this happens after the sheet has animated to it's position
+        /// </summary>
+        OnOpen
+    }
 }

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

@@ -44,8 +44,7 @@
                     <RowDefinition Height="*" />
                 </Grid.RowDefinitions>
 
-                <ContentView x:Name="SheetContent"
-                             Content="{Binding SheetContent}" />
+                <ContentView x:Name="sheetContentView" />
             </Grid>
         </Grid>
     </Frame>

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

@@ -26,14 +26,19 @@ public SheetView(SheetBehavior sheetBehavior)
         /// <summary>
         /// The height that the sheet content needs if it should display all of its content
         /// </summary>
-        internal double SheetContentHeighRequest =>
-            SheetContent.Content.Height + HandleBoxView.Height + OuterSheetFrame.Padding.Top + OuterSheetFrame.Padding.Bottom + OuterSheetFrame.CornerRadius;
+        internal double SheetContentHeightRequest =>
+            sheetContentView.Content != null
+                ? SheetContentView.Content.Height + HandleBoxView.Height + OuterSheetFrame.Padding.Top + OuterSheetFrame.Padding.Bottom +
+                  OuterSheetFrame.CornerRadius
+                : 0;
 
         /// <summary>
         /// The internal outer sheet frame of the view
         /// </summary>
         internal Frame SheetFrame => OuterSheetFrame;
 
+        internal ContentView SheetContentView => sheetContentView;
+
         private double m_newY;
         private void OnDrag(object sender, PanUpdatedEventArgs e)
         {

src/Samples/DIPS.Xamarin.UI.Samples/Controls/Sheet/SheetPage.xaml

@@ -30,7 +30,8 @@
                                 Position="{Binding Position}"
                                 MinPosition="{Binding MinPosition}"
                                 MaxPosition="{Binding MaxPosition}"
-                                BindingContextFactory="{Binding SheetViewModelFactory}">
+                                BindingContextFactory="{Binding SheetViewModelFactory}"
+                                DrawOptions="OnOpen">
                 <StackLayout>
                     <Label Text="{Binding Source={x:Reference entry}, Path=Text}" />
                     <Label Text="{Binding Source={x:Reference entry}, Path=Text}" />