【发布时间】：2021-01-23 23:03:45
【问题描述】：
我在显示数据时遇到问题，我可以在 List 属性中看到我的数据 FieldValue 和 FieldDescriptor 但是我仍然在输出中看到：
绑定：在“ViewModel.ResultPageViewModel”上找不到“Results”属性，目标属性：“Xamarin.Forms.ListView.ItemsSource”
我在水平列表视图中看不到任何数据FieldVisualData，即使我可以在视图模型中看到它们添加到细节并且也找不到命令。
绑定：在“Model.DocumentData”上找不到“EditTextCommand”属性，目标属性：“Xamarin.Forms.TapGestureRecognizer.Command”
也许你看到了我遗漏的东西？
<StackLayout Spacing="0">
<!--Pictures-->
<StackLayout VerticalOptions="Start" Spacing="0" >
<controls:HorizontalScrollList VerticalOptions="Start" HeightRequest="300" x:Name="carouselView" ItemsSource="{Binding Results, Mode=TwoWay}">
<controls:HorizontalScrollList.ItemTemplate>
<DataTemplate>
<Image Source="{Binding Results.FieldVisualData}"
Margin="5">
<!--<Image.GestureRecognizers>
<TapGestureRecognizer
Command="{Binding HandlePreviewTapped, Source={x:Reference vm}}"
CommandParameter="{Binding}"/>
</Image.GestureRecognizers>-->
</Image>
</DataTemplate>
</controls:HorizontalScrollList.ItemTemplate>
</controls:HorizontalScrollList>
</StackLayout>
<StackLayout VerticalOptions="Start" BackgroundColor="{DynamicResource SeparatorLineColor}" Spacing="10">
<!--DocumentData-->
<Label Grid.Row="0" HorizontalOptions="CenterAndExpand" Text="Občanský průkaz" VerticalOptions="End" ></Label>
<StackLayout BackgroundColor="{DynamicResource PageBackgroundColor}" VerticalOptions="FillAndExpand">
<ListView x:Name="list" BackgroundColor="{DynamicResource PageBackgroundColor}"
HasUnevenRows="True"
HorizontalOptions="CenterAndExpand"
VerticalOptions="CenterAndExpand"
VerticalScrollBarVisibility="Never"
CachingStrategy="RecycleElement"
ItemsSource="{Binding Results, Mode=TwoWay}"
SeparatorVisibility="Default"
SelectionMode="None">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<Grid BackgroundColor="{DynamicResource PageBackgroundColor}" Padding="10" >
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="15*"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="12*"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Label Grid.Column="1" Padding="0" Text ="{Binding FieldDescriptor}" Style="{StaticResource SubLabelBlackStyle}" HorizontalOptions="Start" BackgroundColor="{DynamicResource PageBackgroundColor}" HorizontalTextAlignment="Start"/>
<Label Grid.Column="3" Padding="0" Text="{Binding FieldValue}" FontSize="Small" TextColor="#6781a3" BackgroundColor="{DynamicResource PageBackgroundColor}" HorizontalOptions="Start" HorizontalTextAlignment="Start">
<Label.GestureRecognizers>
<TapGestureRecognizer Command="{Binding EditTextCommand}" CommandParameter="{Binding FieldValue}" />
</Label.GestureRecognizers>
</Label>
</Grid>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackLayout>
</StackLayout>
</StackLayout>
public partial class ResultPage : ContentPage
{
public ResultPage(IEnumerable<DocumentData> data)
{
InitializeComponent();
BindingContext = new ResultPageViewModel(data);
//carouselView.ItemsSource = data;
// list.ItemsSource = data;
}
}
public class ResultPageViewModel : BaseViewModel
{
public ObservableCollection<DocumentData> Results { get; } = new ObservableCollection<DocumentData>();
public ICommand EditTextCommand { get; }
object param = "";
public ResultPageViewModel(IEnumerable<DocumentData> data)
{
EditTextCommand = new Command(async () => await EditTextAsync(param));
Load(data);
}
public void Load(IEnumerable<DocumentData> data)
{
foreach (var result in data)
{
var detail = new DocumentData()
{
FieldVisualData = result.FieldVisualData,
FieldDescriptor = result.FieldDescriptor,
FieldValue = result.FieldValue,
};
Results.Add(detail);
}
}
public async Task EditTextAsync(object param)
{
PromptResult pResult = await UserDialogs.Instance.PromptAsync(new PromptConfig
{
InputType = InputType.Password,
Text = param.ToString(),
Title = Resources.AppResources.Password_lbl,
});
}
}
public static readonly BindableProperty ItemTemplateProperty = BindableProperty.Create( "项目模板", 类型（数据模板）， typeof(HorizontalScrollList), 空值， propertyChanged: (bindable, value, newValue) => ((HorizontalScrollList)bindable).Populate());
public static readonly BindableProperty ItemsSourceProperty = BindableProperty.Create(
"ItemsSource",
typeof(IEnumerable),
typeof(HorizontalScrollList),
null,
BindingMode.OneWay,
propertyChanged: (bindable, value, newValue) =>
{
var obs = value as INotifyCollectionChanged;
var self = (HorizontalScrollList)bindable;
if (obs != null)
obs.CollectionChanged -= self.HandleItemChanged;
self.Populate();
obs = newValue as INotifyCollectionChanged;
if (obs != null)
obs.CollectionChanged += self.HandleItemChanged;
});
public IEnumerable ItemsSource
{
get => (IEnumerable)this.GetValue(ItemsSourceProperty);
set => this.SetValue(ItemsSourceProperty, value);
}
public DataTemplate ItemTemplate
{
get => (DataTemplate)this.GetValue(ItemTemplateProperty);
set => this.SetValue(ItemTemplateProperty, value);
}
private bool willUpdate = true;
private void HandleItemChanged(object sender, NotifyCollectionChangedEventArgs eventArgs)
{
if (!willUpdate)
{
willUpdate = true;
Device.BeginInvokeOnMainThread(Populate);
}
}
public HorizontalScrollList()
{
this.Orientation = ScrollOrientation.Horizontal;
}
private void Populate()
{
willUpdate = false;
Content = null;
if (ItemsSource == null || ItemTemplate == null)
{
return;
}
var list = new StackLayout { Orientation = StackOrientation.Horizontal };
foreach (var viewModel in ItemsSource)
{
var content = ItemTemplate.CreateContent();
if (!(content is View) && !(content is ViewCell))
{
throw new Exception($"Invalid visual object {nameof(content)}");
}
var view = content is View ? content as View : ((ViewCell)content).View;
view.BindingContext = viewModel;
list.Children.Add(view);
}
if (list.Children.Count == 0)
{
list.Padding = 20;
list.Children.Add(new Label
{
WidthRequest = (list as VisualElement).Width - 30,
HorizontalOptions = new LayoutOptions(LayoutAlignment.Fill, true),
VerticalOptions = new LayoutOptions(LayoutAlignment.Fill, true),
HorizontalTextAlignment = TextAlignment.Center,
VerticalTextAlignment = TextAlignment.Center,
FontSize = 15,
});
}
Content = list;
}
【问题讨论】：
-
EditTextCommand 是 VM 的属性，而不是 DocumentData。 LIstView 中的每一行都绑定到一个 DocumentData 对象。如果要引用父 VM 上的属性，请参阅docs.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/…
-
根据您的描述，很难确定哪些数据有效，哪些无效。请编辑您的问题，以更清楚地说明哪些特定元素导致了问题
标签： c# xaml xamarin.forms data-binding