如何解决如何在位于 Bindable StackLayouts 内的 ItemTemplateSelector 中引用父 DataTemplates 参数?
这听起来像是一口,但我有一个位于 BindableLayout.ItemTemplateSelector
内的 DataTemplate
。问题是由于某种原因我无法传递 DataTemplate
的 ItemSource
的属性。
在下面'代码'的'数据模板'部分中,我试图从{{1}内访问ItemSource="{Binding CarouselItems}"
内的属性}.但是,除了 <controls:ThoughtEntryDataTemplateSelector>
之外,我无法访问其中的任何内容。
我想将 StaticResource
中的属性传递给它
代码
数据模板
CarouselItems
数据模板选择器
<cards:CarouselView
x:Name="ThoughtCarouselViewer"
IndicatorView="indicatorView"
IsCyclical="False"
ItemsSource="{Binding CarouselItems}">
<cards:CarouselView.ItemTemplate>
<DataTemplate>
<StackLayout>
<Label
x:Name="Title"
FontAttributes="Bold"
Text="{Binding Header}"
TextColor="{StaticResource TextColor}" />
<rv:MaterialFrame
Padding="5"
LightThemeBackgroundColor="#F1F1F1"
Style="{StaticResource CardView}">
<StackLayout BindableLayout.ItemsSource="{Binding Source={RelativeSource AncestorType={x:Type local:ThoughtRecordviewmodel}},Path=ThoughtEntryContainers}" Orientation="Vertical">
<BindableLayout.ItemTemplateSelector>
<controls:ThoughtEntryDataTemplateSelector
ChallengingThought="{StaticResource ChallengingThought}"
distortions="{StaticResource distortions}"
NegativeThought="{StaticResource NegativeThought}"
ThoughtType="{Binding ThoughtEntryType}" /> <============================== What I am trying to access
</BindableLayout.ItemTemplateSelector>
</StackLayout>
</rv:MaterialFrame>
</StackLayout>
</DataTemplate>
</cards:CarouselView.ItemTemplate>
</cards:CarouselView>
轮播物品
public class ThoughtEntryDataTemplateSelector : DataTemplateSelector
{
public DataTemplate NegativeThought { get; set; }
public DataTemplate distortions { get; set; }
public DataTemplate ChallengingThought { get; set; }
public ThoughtEntryType ThoughtType { get; set; }
protected override DataTemplate OnSelectTemplate(object item,BindableObject container)
{
DataTemplate dataTemplate;
if(ThoughtType == ThoughtEntryType.NegativeThought)
{
dataTemplate = NegativeThought;
} else if(ThoughtType == ThoughtEntryType.distortion)
{
dataTemplate = distortions;
} else
{
dataTemplate = ChallengingThought;
}
return dataTemplate;
}
}
解决方法
根据Creating a Xamarin.Forms DataTemplateSelector,我建议您可以为CarouselView选择DataTemplate,而不是StackLayout,然后您可以在OnSelectTemplate
方法中获取当前项目ThoughtEntryType,请参阅我的代码。
<ContentPage.Resources>
<DataTemplate x:Key="ChallengingThought">
<StackLayout >
<Label FontAttributes="Bold" Text="{Binding Header}" />
<Frame CornerRadius="30" BorderColor="Black" BackgroundColor="AliceBlue">
<StackLayout BindableLayout.ItemsSource="{Binding EntryContainers}" Orientation="Vertical">
<Label Text="{Binding .}" />
</StackLayout>
</Frame>
</StackLayout>
</DataTemplate>
<DataTemplate x:Key="NegativeThought" >
<StackLayout>
<Label FontAttributes="Bold" Text="{Binding Header}" />
<Frame CornerRadius="30" BorderColor="Black" BackgroundColor="DarkGray">
<StackLayout BindableLayout.ItemsSource="{Binding EntryContainers}" Orientation="Vertical">
<Label Text="{Binding .}" />
</StackLayout>
</Frame>
</StackLayout>
</DataTemplate>
<DataTemplate x:Key="Distortions">
<StackLayout >
<Label FontAttributes="Bold" Text="{Binding Header}" />
<Frame CornerRadius="30" BorderColor="Black" BackgroundColor="YellowGreen">
<StackLayout BindableLayout.ItemsSource="{Binding EntryContainers}" Orientation="Vertical">
<Label Text="{Binding .}" />
</StackLayout>
</Frame>
</StackLayout>
</DataTemplate>
<local:ThoughtEntryDataTemplateSelector x:Key="EntryDataTemplateSelector"
ChallengingThought="{StaticResource ChallengingThought}"
Distortions="{StaticResource Distortions}"
NegativeThought="{StaticResource NegativeThought}"/>
</ContentPage.Resources>
<ContentPage.Content>
<StackLayout>
<CarouselView
x:Name="ThoughtCarouselViewer"
ItemsSource="{Binding CarouselItems}" ItemTemplate="{StaticResource EntryDataTemplateSelector}">
</CarouselView>
</StackLayout>
</ContentPage.Content>
public partial class Page24 : ContentPage
{
public Page24()
{
InitializeComponent();
this.BindingContext = new ThoughtRecordViewModel();
}
}
public class ThoughtRecordViewModel
{
public ObservableCollection<ThoughtEntryCarouselItems> CarouselItems { get; set; }
public ThoughtRecordViewModel()
{
CarouselItems = new ObservableCollection<ThoughtEntryCarouselItems>()
{
new ThoughtEntryCarouselItems(){Header="header 1",EntryType=ThoughtEntryType.ChallengingThought,EntryContainers=new ObservableCollection<string>(){"1","2","3"}},new ThoughtEntryCarouselItems(){Header="header 2",EntryType=ThoughtEntryType.Distortions,EntryContainers=new ObservableCollection<string>(){"a","b","c"}},new ThoughtEntryCarouselItems(){Header="header 3",EntryType=ThoughtEntryType.NegativeThought,EntryContainers=new ObservableCollection<string>(){"11","22","33"}},new ThoughtEntryCarouselItems(){Header="header 4",EntryContainers=new ObservableCollection<string>(){"112","2222","3333"}},};
}
}
public class ThoughtEntryCarouselItems
{
private string header;
public string Header
{
get => header;
set => header = value;
}
private ThoughtEntryType _EntryType;
public ThoughtEntryType EntryType
{
get => _EntryType;
set => _EntryType = value;
}
public ObservableCollection<string> EntryContainers { get; set; }
}
public enum ThoughtEntryType
{
NegativeThought,Distortions,ChallengingThought
}
public class ThoughtEntryDataTemplateSelector : DataTemplateSelector
{
public DataTemplate NegativeThought { get; set; }
public DataTemplate Distortions { get; set; }
public DataTemplate ChallengingThought { get; set; }
protected override DataTemplate OnSelectTemplate(object item,BindableObject container)
{
DataTemplate dataTemplate=null;
ThoughtEntryCarouselItems carouseitem = (ThoughtEntryCarouselItems)item;
if (carouseitem.EntryType == ThoughtEntryType.NegativeThought)
{
dataTemplate = NegativeThought;
}
else if (carouseitem.EntryType == ThoughtEntryType.Distortions)
{
dataTemplate = Distortions;
}
else if(carouseitem.EntryType == ThoughtEntryType.ChallengingThought)
{
dataTemplate = ChallengingThought;
}
return dataTemplate;
}
}
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