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[iOS] CollectionView2 - empty view - improvements #28119

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[iOS] CollectionView2 - empty view - improvements
kubaflo Mar 1, 2025
8ea0e36
Added a UITest & refactored
kubaflo Mar 3, 2025
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23 changes: 23 additions & 0 deletions src/Controls/src/Core/Handlers/Items2/iOS/ItemsViewController2.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -469,6 +469,7 @@ void UpdateEmptyViewVisibility(bool isEmpty)

if (isEmpty)
{
CollectionView.LayoutIfNeeded();
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@rmarinho rmarinho Apr 16, 2025

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Why do we need to call this if we setting the ContentInset wouldn't t that call layout?

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@kubaflo kubaflo Apr 22, 2025

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Turns out it doesn't. I tried without it on the latest main and it doesn't work

ShowEmptyView();
}
else
Expand Down Expand Up @@ -544,6 +545,7 @@ void HideEmptyView()
}

_emptyUIView.RemoveFromSuperview();
CollectionView.ContentInset = UIEdgeInsets.Zero;

_emptyViewDisplayed = false;
}
Expand All @@ -559,6 +561,24 @@ void TearDownEmptyView()
_emptyViewFormsElement = null;
}

void RemeasureLayout(VisualElement formsElement)
{
if (IsHorizontal)
{
MeasureAndArrange(formsElement, double.PositiveInfinity, CollectionView.Frame.Height);
}
else
{
MeasureAndArrange(formsElement, CollectionView.Frame.Width, double.PositiveInfinity);
}
}

void MeasureAndArrange(VisualElement element, double widthConstraint, double heightConstraint)
{
var request = element.Measure(widthConstraint, heightConstraint);
element.Arrange(new Rect(0, 0, request.Width, request.Height));
}

void LayoutEmptyView()
{
if (!_initialized || _emptyUIView == null || _emptyUIView.Superview == null)
Expand All @@ -568,7 +588,10 @@ void LayoutEmptyView()

var frame = DetermineEmptyViewFrame();

RemeasureLayout(_emptyViewFormsElement);
frame = new CGRect(frame.X, frame.Y, frame.Width, Math.Max(frame.Height, _emptyViewFormsElement.Height));
_emptyUIView.Frame = frame;
CollectionView.ContentInset = new UIEdgeInsets(0, 0, frame.Height, 0);
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@rmarinho rmarinho Apr 16, 2025

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IS this the best way to do it ? Why do we need to inset?

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@kubaflo kubaflo Apr 22, 2025

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Without it, a CollectionView with an empty view whose height exceeds the frame won't scroll.


if (_emptyViewFormsElement != null && ((IElementController)ItemsView).LogicalChildren.IndexOf(_emptyViewFormsElement) != -1)
_emptyViewFormsElement.Layout(frame.ToRectangle());
Expand Down
20 changes: 20 additions & 0 deletions src/Controls/tests/TestCases.HostApp/Issues/Issue28118.xaml
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@@ -0,0 +1,20 @@
<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns:controls="clr-namespace:Maui.Controls.Sample.Issues"
xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="Maui.Controls.Sample.Issues.Issue28118">
<Grid RowDefinitions="*">
<CollectionView AutomationId="CollectionView">
<CollectionView.EmptyView>
<VerticalStackLayout>
<ContentView HeightRequest="500"
BackgroundColor="Red"/>
<ContentView HeightRequest="500"
BackgroundColor="Blue"/>
<Label Text="Success"
AutomationId="SuccessLabel"/>
</VerticalStackLayout>
</CollectionView.EmptyView>
</CollectionView>
</Grid>
</ContentPage>
9 changes: 9 additions & 0 deletions src/Controls/tests/TestCases.HostApp/Issues/issue28118.xaml.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
namespace Maui.Controls.Sample.Issues;
[Issue(IssueTracker.Github, 28118, "CollectionView - empty view issues", PlatformAffected.iOS)]
public partial class Issue28118 : ContentPage
{
public Issue28118()
{
InitializeComponent();
}
}
22 changes: 22 additions & 0 deletions src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue28118.cs
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@@ -0,0 +1,22 @@
using NUnit.Framework;
using UITest.Appium;
using UITest.Core;

namespace Microsoft.Maui.TestCases.Tests.Issues;
public class Issue28118 : _IssuesUITest
{
public Issue28118(TestDevice testDevice) : base(testDevice)
{
}

public override string Issue => "CollectionView - empty view issues";

[Test]
[Category(UITestCategories.CollectionView)]
public void EmptyViewShouldScroll()
{
App.WaitForElement("CollectionView");
App.ScrollDown("CollectionView", ScrollStrategy.Gesture, 0.5);
App.WaitForElement("SuccessLabel");
}
}
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