[iOS] Fix missing partial columns in horizontal grid layout (#6241)

* Create repro

* Work around UICollectionViewFlowLayout bug to display partial columns; fixes #6077
Fix content inset behaviors when dealing with safe area on newer iOS versions

* Add check for case where there is only a single partial column

* Works better if I don't forget the return statement

* Split up tests to make it easier to determine what failed

* Fix bounds exception when changing to a smaller ItemsSource

* Add preserve attributes so the linker won't ruin my UI test

* Fix missing using after rebase
This commit is contained in:
E.Z. Hart 2019-06-17 15:07:32 -06:00 коммит произвёл Samantha Houts
Родитель 019959aeda
Коммит 9eb316105f
6 изменённых файлов: 278 добавлений и 14 удалений

Просмотреть файл

@ -0,0 +1,139 @@
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using Xamarin.Forms.CustomAttributes;
using Xamarin.Forms.Internals;
using Xamarin.Forms.PlatformConfiguration;
using Xamarin.Forms.PlatformConfiguration.iOSSpecific;
#if UITEST
using Xamarin.Forms.Core.UITests;
using Xamarin.UITest;
using NUnit.Framework;
#endif
namespace Xamarin.Forms.Controls.Issues
{
#if UITEST
[NUnit.Framework.Category(UITestCategories.CollectionView)]
#endif
[Preserve(AllMembers = true)]
[Issue(IssueTracker.Github, 6077, "CollectionView (iOS) using horizontal grid does not display last column of uneven item count", PlatformAffected.iOS)]
public class Issue6077 : TestNavigationPage
{
[Preserve(AllMembers = true)]
public class MainViewModel : INotifyPropertyChanged
{
readonly IList<ItemModel> _items;
public ObservableCollection<ItemModel> Items { get; private set; }
public MainViewModel()
{
_items = new List<ItemModel>();
CreateItemsCollection();
}
void CreateItemsCollection(int items = 5)
{
for (int n = 0; n < items; n++)
{
_items.Add(new ItemModel
{
Title = $"Item {n + 1}",
});
}
Items = new ObservableCollection<ItemModel>(_items);
}
protected bool SetProperty<T>(ref T backingStore, T value,
[CallerMemberName]string propertyName = "",
Action onChanged = null)
{
if (EqualityComparer<T>.Default.Equals(backingStore, value))
return false;
backingStore = value;
onChanged?.Invoke();
OnPropertyChanged(propertyName);
return true;
}
#region INotifyPropertyChanged
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged([CallerMemberName] string propertyName = "")
{
var changed = PropertyChanged;
if (changed == null)
return;
changed.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
}
[Preserve(AllMembers = true)]
public class ItemModel
{
public string Title { get; set; }
}
ContentPage CreateRoot()
{
var page = new ContentPage { Title = "Issue6077" };
var cv = new CollectionView { ItemSizingStrategy = ItemSizingStrategy.MeasureAllItems };
var itemsLayout = new GridItemsLayout(3, ItemsLayoutOrientation.Horizontal);
cv.ItemsLayout = itemsLayout;
var template = new DataTemplate(() => {
var grid = new Grid { HeightRequest = 100, WidthRequest = 50, BackgroundColor = Color.AliceBlue };
grid.RowDefinitions = new RowDefinitionCollection { new RowDefinition { Height = new GridLength(100) } };
grid.ColumnDefinitions = new ColumnDefinitionCollection { new ColumnDefinition { Width = new GridLength(50) } };
var label = new Label { };
label.SetBinding(Label.TextProperty, new Binding("Title"));
var content = new ContentView { Content = label };
grid.Children.Add(content);
return grid;
});
cv.ItemTemplate = template;
cv.SetBinding(ItemsView.ItemsSourceProperty, new Binding("Items"));
page.Content = cv;
BindingContext = new MainViewModel();
return page;
}
protected override void Init()
{
#if APP
Device.SetFlags(new List<string>(Device.Flags ?? new List<string>()) { "CollectionView_Experimental" });
PushAsync(CreateRoot());
#endif
}
#if UITEST
[Test]
public void LastColumnShouldBeVisible()
{
// If the partial column shows up, then Item 5 will be in it
RunningApp.WaitForElement("Item 5");
}
#endif
}
}

Просмотреть файл

@ -964,6 +964,7 @@
<Compile Include="$(MSBuildThisFileDirectory)Issue5132.cs" />
<Compile Include="$(MSBuildThisFileDirectory)Issue5888.cs" />
<Compile Include="$(MSBuildThisFileDirectory)Issue6334.cs" />
<Compile Include="$(MSBuildThisFileDirectory)Issue6077.cs" />
</ItemGroup>
<ItemGroup>
<EmbeddedResource Include="$(MSBuildThisFileDirectory)Bugzilla22229.xaml">

Просмотреть файл

@ -49,22 +49,25 @@ namespace Xamarin.Forms.Core.UITests
// "ScrollToItemCode,HorizontalList", "ScrollToItemCode,VerticalList", "ScrollToItemCode,HorizontalGrid", "ScrollToItemCode,VerticalGrid",
// }, 19, 3)]
//[TestCase("Snap Points", new string[] { "SnapPointsCode,HorizontalList", "SnapPointsCode,VerticalList", "SnapPointsCode,HorizontalGrid", "SnapPointsCode,VerticalGrid" }, 19, 2)]
[TestCase("Observable Collection", new string[] { "Add/RemoveItemsList", "Add/RemoveItemsGrid" }, 19, 6)]
[TestCase("Default Text", new string[] { "VerticalListCode", "HorizontalListCode", "VerticalGridCode", "HorizontalGridCode" }, 101, 11)]
[TestCase("DataTemplate", new string[] { "VerticalListCode", "HorizontalListCode", "VerticalGridCode", "HorizontalGridCode" }, 19, 6)]
public void VisitAndUpdateItemsSource(string collectionTestName, string[] subGalleries, int firstItem, int lastItem)
[TestCase("Observable Collection", "Add/RemoveItemsList", 19, 6)]
[TestCase("Observable Collection", "Add/RemoveItemsGrid", 19, 6)]
[TestCase("Default Text", "VerticalListCode", 101, 11)]
[TestCase("Default Text", "HorizontalListCode", 101, 11)]
[TestCase("Default Text", "VerticalGridCode", 101, 11)]
[TestCase("Default Text", "HorizontalGridCode", 101, 11)]
[TestCase("DataTemplate", "VerticalListCode", 19, 6)]
[TestCase("DataTemplate", "HorizontalListCode", 19, 6)]
[TestCase("DataTemplate", "VerticalGridCode", 19, 6)]
[TestCase("DataTemplate", "HorizontalGridCode", 19, 6)]
public void VisitAndUpdateItemsSource(string collectionTestName, string subGallery, int firstItem, int lastItem)
{
VisitInitialGallery(collectionTestName);
foreach (var gallery in subGalleries)
{
if (gallery == "FilterItems")
continue;
VisitSubGallery(gallery, !gallery.Contains("Horizontal"), $"Item: {firstItem}", $"Item: {lastItem}", lastItem - 1, true, false);
VisitSubGallery(subGallery, !subGallery.Contains("Horizontal"), $"Item: {firstItem}", $"Item: {lastItem}", lastItem - 1, true, false);
App.NavigateBack();
}
}
//[TestCase("ScrollTo", new string[] {
// "ScrollToIndexCode,HorizontalList", "ScrollToIndexCode,VerticalList", "ScrollToIndexCode,HorizontalGrid", "ScrollToIndexCode,VerticalGrid",

Просмотреть файл

@ -1,7 +1,7 @@
using System;
using System.ComponentModel;
using System.Diagnostics;
using CoreGraphics;
using Foundation;
using UIKit;
namespace Xamarin.Forms.Platform.iOS
@ -43,7 +43,7 @@ namespace Xamarin.Forms.Platform.iOS
ConstrainedDimension = (availableSpace - spacing) / _itemsLayout.Span;
// TODO hartez 2018/09/12 14:52:24 We need to truncate the decimal part of ConstrainedDimension
// We need to truncate the decimal part of ConstrainedDimension
// or we occasionally run into situations where the rows/columns don't fit
// But this can run into situations where we have an extra gap because we're cutting off too much
// and we have a small gap; need to determine where the cut-off is that leads to layout dropping a whole row/column
@ -58,5 +58,107 @@ namespace Xamarin.Forms.Platform.iOS
ConstrainedDimension = (int)ConstrainedDimension;
DetermineCellSize();
}
/* `CollectionViewContentSize` and `LayoutAttributesForElementsInRect` are overridden here to work around what
* appears to be a bug in the UICollectionViewFlowLayout implementation: for horizontally scrolling grid
* layouts with auto-sized cells, trailing items which don't fill out a column are never displayed.
* For example, with a span of 3 and either 4 or 5 items, the resulting layout looks like
*
* Item1
* Item2
* Item3
*
* But with 6 items, it looks like
*
* Item1 Item4
* Item2 Item5
* Item3 Item6
*
* IOW, if there are not enough items to fill out the last column, the last column is ignored.
*
* These overrides detect and correct that situation.
*/
public override CGSize CollectionViewContentSize
{
get
{
if (!NeedsPartialColumnAdjustment())
{
return base.CollectionViewContentSize;
}
var contentSize = base.CollectionViewContentSize;
// Add space for the missing column at the end
var correctedSize = new CGSize(contentSize.Width + EstimatedItemSize.Width, contentSize.Height);
return correctedSize;
}
}
public override UICollectionViewLayoutAttributes[] LayoutAttributesForElementsInRect(CGRect rect)
{
if (!NeedsPartialColumnAdjustment())
{
return base.LayoutAttributesForElementsInRect(rect);
}
// When we implement Groups, we'll have to iterate over all of them to adjust and this will
// be a lot more complicated. But until then, we only have to worry about section 0
int section = 0;
var fullColumns = base.LayoutAttributesForElementsInRect(rect);
var itemCount = CollectionView.NumberOfItemsInSection(section);
if (fullColumns.Length == itemCount)
{
return fullColumns;
}
var missingCellCount = itemCount % _itemsLayout.Span;
UICollectionViewLayoutAttributes[] allCells = new UICollectionViewLayoutAttributes[fullColumns.Length + missingCellCount];
fullColumns.CopyTo(allCells, 0);
for (int n = fullColumns.Length; n < allCells.Length; n++)
{
allCells[n] = LayoutAttributesForItem(NSIndexPath.FromItemSection(n, section));
}
return allCells;
}
bool NeedsPartialColumnAdjustment(int section = 0)
{
if (ScrollDirection == UICollectionViewScrollDirection.Vertical)
{
// The bug only occurs with Horizontal scrolling
return false;
}
if (EstimatedItemSize.IsEmpty)
{
// The bug only occurs when using Autolayout; with a set ItemSize, we don't have to worry about it
return false;
}
var itemCount = CollectionView.NumberOfItemsInSection(section);
if (itemCount < _itemsLayout.Span)
{
// If there is just one partial column, no problem; UICollectionViewFlowLayout gets it right
return false;
}
if (itemCount % _itemsLayout.Span == 0)
{
// All of the columns are full; the bug only occurs when we have a partial column
return false;
}
return true;
}
}
}

Просмотреть файл

@ -27,6 +27,15 @@ namespace Xamarin.Forms.Platform.iOS
: UICollectionViewScrollDirection.Vertical;
Initialize(scrollDirection);
if (Forms.IsiOS11OrNewer)
{
// `ContentInset` is actually the default value, but I'm leaving this here as a note to
// future maintainers; it's likely that someone will want a Platform Specific to change this behavior
// (Setting it to `SafeArea` lets you do the thing where the header/footer of your UICollectionView
// fills the screen width in landscape while your items are automatically shifted to avoid the notch)
SectionInsetReference = UICollectionViewFlowLayoutSectionInsetReference.ContentInset;
}
}
protected override void Dispose(bool disposing)

Просмотреть файл

@ -85,6 +85,16 @@ namespace Xamarin.Forms.Platform.iOS
UpdateLayout();
ItemsViewController = CreateController(newElement, _layout);
if (Forms.IsiOS11OrNewer)
{
// We set this property to keep iOS from trying to be helpful about insetting all the
// CollectionView content when we're in landscape mode (to avoid the notch)
// The SetUseSafeArea Platform Specific is already taking care of this for us
// That said, at some point it's possible folks will want a PS for controlling this behavior
ItemsViewController.CollectionView.ContentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentBehavior.Never;
}
SetNativeControl(ItemsViewController.View);
ItemsViewController.CollectionView.BackgroundColor = UIColor.Clear;
ItemsViewController.UpdateEmptyView();