Fix Snackbar layout #1901

Author: VladislavAntonyuk

samples/CommunityToolkit.Maui.Sample/Pages/Alerts/SnackbarPage.xaml

@@ -15,9 +15,14 @@
     </pages:BasePage.Resources>
 
     <VerticalStackLayout Spacing="12">
+        <Button x:Name="DisplayCustomSnackbarButton2"
+                Text="Display Custom Snackbar"
+                Clicked="DisplayCustomSnackbarButtonClicked2"
+                TextColor="{Binding Source={RelativeSource Self}, Path=BackgroundColor, Converter={StaticResource ColorToColorForTextConverter}, x:DataType=Button}"/> 
+
 
         <Label Text="The Snackbar is a timed alert that appears at the bottom of the screen by default. It is dismissed after a configurable duration of time. Snackbar is fully customizable and can be anchored to any IView." 
-                LineBreakMode = "WordWrap" />
+               LineBreakMode = "WordWrap" />
 
         <Label Text="Windows uses toast notifications to display snackbar. Make sure you switched off Focus Assist."
                IsVisible="{OnPlatform Default='false', WinUI='true'}"/>

samples/CommunityToolkit.Maui.Sample/Pages/Alerts/SnackbarPage.xaml.cs

@@ -82,6 +82,25 @@ async void DisplayCustomSnackbarButtonClicked(object? sender, EventArgs args)
 			throw new NotSupportedException($"{nameof(DisplayCustomSnackbarButton)}.{nameof(ITextButton.Text)} Not Recognized");
 		}
 	}
+	async void DisplayCustomSnackbarButtonClicked2(object sender, EventArgs e)
+	{
+		var options = new SnackbarOptions
+		{
+			BackgroundColor = Colors.Red,
+			TextColor = Colors.Green,
+			CharacterSpacing = 1,
+			ActionButtonFont = Font.SystemFontOfSize(14),
+			ActionButtonTextColor = Colors.Yellow,
+			CornerRadius = new CornerRadius(10),
+			Font = Font.SystemFontOfSize(14),
+		};
+		await DisplayCustomSnackbarButton2.DisplaySnackbar(
+			"This is a customized Snackbar",
+			() => DisplayCustomSnackbarButton2.BackgroundColor = Colors.Blue,
+			"Close",
+			TimeSpan.FromSeconds(5),
+			options);
+	}
 
 	void Snackbar_Dismissed(object? sender, EventArgs e)
 	{

src/CommunityToolkit.Maui.Core/Views/Alert/AlertView.macios.cs

@@ -8,6 +8,7 @@ namespace CommunityToolkit.Maui.Core.Views;
 /// </summary>
 public class AlertView : UIView
 {
+	const int defaultSpacing = 10;
 	readonly List<UIView> children = [];
 
 	/// <summary>
@@ -55,23 +56,37 @@ public void Setup()
 		ConstraintInParent();
 	}
 
-	void ConstraintInParent()
+	/// <inheritdoc />
+	public override void LayoutSubviews()
 	{
+		base.LayoutSubviews();
 		_ = Container ?? throw new InvalidOperationException($"{nameof(AlertView)}.{nameof(Initialize)} not called");
 
-		const int defaultSpacing = 10;
 		if (AnchorView is null)
 		{
 			this.SafeBottomAnchor().ConstraintEqualTo(ParentView.SafeBottomAnchor(), -defaultSpacing).Active = true;
 			this.SafeTopAnchor().ConstraintGreaterThanOrEqualTo(ParentView.SafeTopAnchor(), defaultSpacing).Active = true;
 		}
 		else
 		{
-			this.SafeBottomAnchor().ConstraintEqualTo(AnchorView.SafeTopAnchor(), -defaultSpacing).Active = true;
+			var anchorViewPosition = AnchorView.Superview.ConvertRectToView(AnchorView.Frame, null);
+			if (anchorViewPosition.Top < Container.Frame.Height + SafeAreaLayoutGuide.LayoutFrame.Bottom)
+			{
+				this.SafeTopAnchor().ConstraintEqualTo(AnchorView.SafeBottomAnchor(), defaultSpacing).Active = true;
+			}
+			else
+			{
+				this.SafeBottomAnchor().ConstraintEqualTo(AnchorView.SafeTopAnchor(), -defaultSpacing).Active = true;
+			}
 		}
+	}
+
+	void ConstraintInParent()
+	{
+		_ = Container ?? throw new InvalidOperationException($"{nameof(AlertView)}.{nameof(Initialize)} not called");
 
-		this.SafeLeadingAnchor().ConstraintGreaterThanOrEqualTo(ParentView.SafeLeadingAnchor(), defaultSpacing).Active = true;
-		this.SafeTrailingAnchor().ConstraintLessThanOrEqualTo(ParentView.SafeTrailingAnchor(), -defaultSpacing).Active = true;
+		this.SafeLeadingAnchor().ConstraintEqualTo(ParentView.SafeLeadingAnchor(), defaultSpacing).Active = true;
+		this.SafeTrailingAnchor().ConstraintEqualTo(ParentView.SafeTrailingAnchor(), -defaultSpacing).Active = true;
 		this.SafeCenterXAnchor().ConstraintEqualTo(ParentView.SafeCenterXAnchor()).Active = true;
 
 		Container.SafeLeadingAnchor().ConstraintEqualTo(this.SafeLeadingAnchor(), defaultSpacing).Active = true;