NaN不是宽度的有效值

Question

在Xamarin.Forms 2.3.4.192-pre2中，我创建了一个自定义ViewCell，它使用网格作为Xamarin.Forms.ListView的DataTemplate。

当加载ListView时，它会抛出System.ArgumentException: NaN is not a valid value for width。

我已经找到了Xamarin.Forms源代码中的错误，但是我不知道为什么宽度是NaN

错误

System.ArgumentException: NaN不是宽度的有效值 Xamarin.Forms.VisualElement.GetSizeRequest(double (双宽，双高) Xamarin.Forms.StackLayout.CompressHorizontalLayout(StackLayout.LayoutInformation布局(双widthConstraint，双heightConstraint，MeasureFlags标志)Xamarin.Forms.Size.Size(双宽度，双高度) Xamarin.Forms.StackLayout.CalculateLayout(StackLayout.LayoutInformation布局，双面widthConstraint，双heightConstraint，MeasureFlags标志)Xamarin.Forms.Size.Size布局，双层widthConstraint，双heightConstraint，MeasureFlags标志)Xamarin.Forms.StackLayout.CalculateLayout(StackLayout.LayoutInformation布局，双人x，双人y，双heightConstraint，bool，EN4# x，双y，双宽，双高) Xamarin.Forms.VisualElement.SizeAllocated(double (双宽，双高) Xamarin.Forms.Layout.UpdateChildrenLayout() Xamarin.Forms.Layout.OnSizeAllocated(双宽，双高)Xamarin.Forms.VisualElement.SetSize(双宽，双高)Xamarin.Forms.VisualElement.SetSize(双宽，双高)Xamarin.Forms.VisualElement.Layout(矩形界) Xamarin.Forms.Layout.LayoutChildIntoBoundingRegion(VisualElement子区域，矩形区域)Xamarin.Forms.Grid.LayoutChildren(双x，双y，双宽度，(双高) Xamarin.Forms.VisualElement.SizeAllocated(double宽度(双高)Xamarin.Forms.Layout.OnSizeAllocated(双宽，双高)Xamarin.Forms.VisualElement.SetSize(双宽，双高)Xamarin.Forms.Layout.OnSizeAllocated值)Xamarin.Forms.VisualElement.Layout(矩形边界) Xamarin.Forms.Layout.LayoutChildIntoBoundingRegion(VisualElement子区域) Xamarin.Forms.Platform.iOS.ViewCellRenderer.ViewTableCell.LayoutSubviews() Xamarin.Forms.Platform.iOS.CellTableViewCell.GetNativeCell(UITableView tableView，Xamarin.Forms.Platform.iOS.ListViewRenderer.ListViewDataSource.GetCell(UITableView tableView，NSIndexPath indexPath) UIKit.UIApplication.UIApplicationMain(int，string[]，intptr，IntPtr )(包装托管到本地) UIKit.UIApplication.Main(string[] args，IntPtr主体，IntPtr委托)UIApplication.cs:79 UIKit.UIApplication.Main(string[] args，string principalClassName，string delegateClassName)principalClassName(Args)

代码

我在GitHub：https://github.com/brminnick/Xamarin.Forms-NaN-is-not-a-valid-value-for-width-reproduction上把一个复制放在这个存储库中

ListView

var listView = new ListView(ListViewCachingStrategy.RecycleElement)
{
    BackgroundColor = Color.White,
    RowHeight = 200,
    ItemTemplate = new DataTemplate(typeof(PuzzleCellCardView)),
    SeparatorColor = Color.Transparent
};

ViewCell

public class PuzzleCellCardView : ViewCell
{
    Image _puzzleImage;
    Label _punNumberValueLabel;
    Image _questionMarkImage;
    Image _checkImage;

    public PuzzleCellCardView()
    {
        var puzzleImage = new Image
        {
            HeightRequest = 150,
            BackgroundColor = Color.White
        };

        var punNumberTextLabel = new Label
        {
            Text = " Pun Number",
            Style = StyleConstants.LabelStyle
        };

        _punNumberValueLabel = new Label
        {
            Style = StyleConstants.LabelStyle
        };

        var puzzleNumberStackLayout = new StackLayout
        {
            Children = {
                punNumberTextLabel,
                _punNumberValueLabel
            },
            Orientation = StackOrientation.Horizontal,
            BackgroundColor = Color.White
        };

        _questionMarkImage = new Image
        {
            Source = App.ImageConstants.QuestionMark,
            MinimumHeightRequest = 100,
            BackgroundColor = Color.White
        };

        _checkImage = new Image
        {
            Source = App.ImageConstants.Check,
            MinimumHeightRequest = 100,
            BackgroundColor = Color.White
        };

        var whitePuzzleNumberBackgroundBoxView = new BoxView
        {
            BackgroundColor = Color.White
        };

        var cellGridLayout = new Grid
        {
            BackgroundColor = Color.Black,
            Padding = new Thickness(2),
            RowSpacing = 2,
            ColumnSpacing = 1,
            VerticalOptions = LayoutOptions.Fill,

            RowDefinitions = {
                new RowDefinition{ Height = new GridLength (20, GridUnitType.Absolute) },
                new RowDefinition{ Height = new GridLength (150, GridUnitType.Absolute) }
            },
            ColumnDefinitions = {
                new ColumnDefinition{ Width = new GridLength (1, GridUnitType.Star) },
                new ColumnDefinition{ Width = new GridLength (1, GridUnitType.Star) }
            }
        };
        cellGridLayout.Children.Add(whitePuzzleNumberBackgroundBoxView, 0, 0);
        Grid.SetColumnSpan(whitePuzzleNumberBackgroundBoxView, 2);

        cellGridLayout.Children.Add(puzzleNumberStackLayout, 0, 0);
        Grid.SetColumnSpan(puzzleNumberStackLayout, 2);

        cellGridLayout.Children.Add(_puzzleImage, 0, 1);

        cellGridLayout.Children.Add(_checkImage, 1, 1);
        cellGridLayout.Children.Add(_questionMarkImage, 1, 1);

        if (Device.OS == TargetPlatform.Android)
            _puzzleImage.InputTransparent = true;

        View = cellGridLayout;
    }
}

Answer 1

这似乎是Xamarin.Forms v2.3.4.192-pre2的回归。

使用Xamarin.Forms v2.3.3.180时不会引发异常。

我通过Bugzilla：bug.cgi?id=52533将错误提交给了bug.cgi?id=52533团队

更新: Xamarin.Forms 2.3.4.214-pre5中修复了此错误

Answer 2

添加一个容器(例如: frame)并为这个容器指定宽度，

<Frame x:Name="AutoCompleterContainer" Grid.Row="1" WidthRequest="400">
    <telerikInput:RadAutoComplete ....
</Frame>