问题描述
在绑定项目源之后，我正在以编程方式更新CollectionView.ItemsLayout，它在Android上工作正常，但在iOS上却无法正常工作。 iOS应用程序未引发任何异常/错误，但该应用程序挂起，当我查看输出窗口时，收到以下消息：
在计算布局（即重入调用）的过程中，已检测到尝试更新布局信息。这将导致意外行为或崩溃。如果在调出代表时触发了布局传递，则可能会发生这种情况。 UICollectionViewFlowLayout实例为（
）
在进行prepareLayout调用（即重入调用）时准备布局的尝试已被忽略。请提交错误。 UICollectionView实例为（
; layer = ; contentOffset：{0， 0}； contentSize：{1、0}； adjustedContentInset：{0、0、0、0}；布局： ；数据源： >）
我的XAML：
<ScrollView>
<StackLayout Margin="0,5,0">
<Label x:Name="NoItemLabel" IsVisible="False"
Text="{languages:Translate EmptyListMessage}"
Style="{DynamicResource NoItemListLabel}" />
<!-- Product List -->
<CollectionView
VerticalScrollBarVisibility="Never" VerticalOptions="StartAndExpand"
HorizontalOptions="StartAndExpand"
x:Name="ItemsList" IsVisible="False" SelectionMode="Single"
SelectionChanged="ItemsList_SelectionChanged">
<CollectionView.ItemsLayout>
<GridItemsLayout x:Name="ItemsListItemsLayout" Span="{x:OnIdiom Tablet=3,Phone=2}" Orientation="Vertical" HorizontalItemSpacing="10" VerticalItemSpacing="10" />
</CollectionView.ItemsLayout>
<!--PAGINATION-->
<CollectionView.Header>
<Label
x:Name="ShowingTitle" Margin="5,10" TextColor="{DynamicResource LightGrayColor}"
FontSize="{StaticResource Medium}" HorizontalOptions="EndAndExpand"
VerticalOptions="CenterandExpand" HorizontalTextAlignment="End" />
</CollectionView.Header>
<CollectionView.Footer>
<StackLayout Orientation="Horizontal" HorizontalOptions="FillAndExpand" Margin="0,10">
<Frame
x:Name="PrevIoUsPageFrame" IsVisible="False"
Padding="5,10,5" Margin="0"
HorizontalOptions="StartAndExpand" VerticalOptions="CenterandExpand"
Style="{DynamicResource ButtonFrameStyle}">
<Frame.GestureRecognizers>
<TapGestureRecognizer Tapped="PrevIoUsPage_Tapped" />
</Frame.GestureRecognizers>
<StackLayout Orientation="Horizontal">
<Image
Aspect="AspectFit" HorizontalOptions="EndAndExpand" Margin="0">
<Image.source>
<FontimageSource
FontFamily="{DynamicResource MaterialFontFamily}"
Glyph="{x:Static font:FontAwesomeIcons.ThinLeft}" />
</Image.source>
</Image>
<Label
FontSize="{StaticResource Small}"
Style="{DynamicResource ButtonLabelStyle}"
Text="{languages:Translate PrevIoUs}" Margin="-10,0"
TextColor="{DynamicResource SameThemeColor}" />
</StackLayout>
</Frame>
<Label
x:Name="PageNumber" HorizontalTextAlignment="Center"
FontSize="{StaticResource Medium}" TextColor="{DynamicResource DarkGrayColor}"
VerticalOptions="CenterandExpand" HorizontalOptions="CenterandExpand" />
<Frame
x:Name="NextPageFrame" IsVisible="False"
Padding="10,5" Margin="0"
HorizontalOptions="EndAndExpand" VerticalOptions="CenterandExpand"
Style="{DynamicResource ButtonFrameStyle}">
<Frame.GestureRecognizers>
<TapGestureRecognizer Tapped="NextPage_Tapped" />
</Frame.GestureRecognizers>
<StackLayout Orientation="Horizontal">
<Label
FontSize="{StaticResource Small}"
Style="{DynamicResource ButtonLabelStyle}"
Text="{languages:Translate Next}" Margin="0,-10,0" />
<Image
Aspect="AspectFit" HorizontalOptions="EndAndExpand" Margin="0">
<Image.source>
<FontimageSource
FontFamily="{DynamicResource MaterialFontFamily}"
Glyph="{x:Static font:FontAwesomeIcons.ThinRight}"
Color="{DynamicResource SameThemeColor}" />
</Image.source>
</Image>
</StackLayout>
</Frame>
</StackLayout>
</CollectionView.Footer>
<!--PAGINATION-->
<CollectionView.ItemTemplate>
<DataTemplate>
<Frame
Margin="5" x:Name="productViewCake"
Padding="5" BackgroundColor="{DynamicResource SameThemeColor}"
CornerRadius="10" HasShadow="False" HorizontalOptions="StartAndExpand"
VerticalOptions="StartAndExpand">
<StackLayout>
<Image
Aspect="AspectFit"
HeightRequest="120"
Source="{Binding ItemID,Converter={StaticResource ImagePathConverter},ConverterParameter='Item'}" />
<Label
FontFamily="{DynamicResource OpenSansSemiBold}" FontSize="{StaticResource Small}"
Text="{Binding ItemName}" LineBreakMode="TailTruncation"
Margin="0" Padding="0"
TextColor="{DynamicResource DarkGrayColor}"
VerticalOptions="CenterandExpand" />
<Label
FontFamily="{DynamicResource OpenSansLight}"
FontSize="{StaticResource Small}"
HorizontalOptions="Start" Margin="0" Padding="0"
Text="{Binding ItemCategory.ItemCategoryName}" LineBreakMode="TailTruncation"
TextColor="{DynamicResource LightGrayColor}"
VerticalOptions="CenterandExpand" />
<Label
FontFamily="{DynamicResource OpenSansBold}"
FontSize="{StaticResource normal}"
HorizontalOptions="Start"
Text="{Binding CurrentPrice}"
TextColor="{DynamicResource AppThemeColor}"
VerticalOptions="CenterandExpand" />
</StackLayout>
</Frame>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
</StackLayout>
</ScrollView>
我的XAML.cs：
internal async Task BindItems()
{
var jsonResponse = await WebApiService.ProcessRequestAsync(JsonMethods.GetItems);
var data = (JObject)JsonConvert.DeserializeObject(jsonResponse.ResponseJson);
int totalItems = data["TotalCount"].Value<int>();
var list = data["Itemmasters"].Value<JToken>().ToObject<List<Itemmaster>>();
ItemsList.RemoveBinding(ItemsView.ItemsSourceProperty);
//ItemsList.ItemsSource = null;
if (list.Count > 0)
{
ItemsList.SetBinding(ItemsView.ItemsSourceProperty,new Binding("list"));
//ItemsList.ItemsSource = list;
ItemsList.IsVisible = true;
NoItemLabel.IsVisible = false;
int widthPerElement = 170;
int span = (Application.Current.MainPage.Width / widthPerElement).ToProperInt();
ItemsListItemsLayout.Span = span;
totalPages = (totalItems / takeCount) + 1;
currentPage = (currentStartingCount / takeCount) + 1;
int showingTo = currentStartingCount + takeCount;
if (showingTo > totalItems) showingTo = totalItems;
ShowingTitle.Text = string.Format(TranslateExtension.Translate("ShowingTitle"),currentStartingCount + 1,showingTo,totalItems,TranslateExtension.Translate("Products").ToLowerInvariant());
PageNumber.Text = string.Format(TranslateExtension.Translate("PageNumber"),currentPage,totalPages);
//prevIoUs frame
if (currentPage <= 1 || totalPages <= 1)
{
PrevIoUsPageFrame.IsVisible = false;
}
else
{
PrevIoUsPageFrame.IsVisible = true;
}
//next frame
if (currentPage >= totalPages || totalPages <= 1)
{
NextPageFrame.IsVisible = false;
}
else
{
NextPageFrame.IsVisible = true;
}
}
else
{
ItemsList.IsVisible = false;
NoItemLabel.IsVisible = true;
}
}
解决方法
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