How can I access a specific collectionview child? In this case, the label “DataCadastroLabel”

Question

I want to change the value of VerticalOptions.

I can't directly access this label, even if I pass its name DataCadastroLabel.

These layout changes are only to adapt some components to the device's landscape mode

XAML

<CollectionView x:Name="ItemsListView"
                                ItemsSource="{Binding Notificacoes}"
                                SelectionMode="None"
                                ItemsUpdatingScrollMode="KeepItemsInView"
                                VerticalScrollBarVisibility="Never"
                                HorizontalScrollBarVisibility="Never"
                                IsGrouped="True">
                    <CollectionView.GroupHeaderTemplate>
                        <DataTemplate x:DataType="model:NotificacaoGrupoData">
                            <Label Text="{Binding Data_agrupada}"
                                   FontSize="20"
                                   FontAttributes="Bold"
                                   HorizontalTextAlignment="Center"
                                   Padding="0,15,0,15"/>
                        </DataTemplate>
                    </CollectionView.GroupHeaderTemplate>

                    <CollectionView.ItemTemplate>
                        <DataTemplate>
                            <StackLayout x:DataType="model:Notificacao">
                                <StackLayout Orientation="Horizontal">
                                    <Image Source="logo"
                                           HeightRequest="40"
                                           Margin="0,0,5,0"
                                           VerticalOptions="CenterAndExpand"/>

                                    <StackLayout VerticalOptions="CenterAndExpand">
                                        <StackLayout Orientation="Horizontal">
                                            <Label Text="{Binding app_nome}" 
                                                   LineBreakMode="NoWrap" 
                                                   Style="{DynamicResource ListItemTextStyle}" 
                                                   FontSize="20" 
                                                   FontAttributes="Bold"
                                                   VerticalTextAlignment="Center"
                                                   HorizontalOptions="StartAndExpand"/>

                                            <Label Text="{Binding dt_cadastro_hora}"
                                                   x:Name="DataCadastroLabel"
                                                   LineBreakMode="NoWrap" 
                                                   Style="{DynamicResource ListItemTextStyle}" 
                                                   FontSize="13"
                                                   FontAttributes="Bold"
                                                   VerticalOptions="CenterAndExpand"
                                                   Margin="0,0,20,0"/>
                                        </StackLayout>

                                        <Label Text="{Binding mensagem}"
                                               TextType="Html"
                                               WidthRequest="290"
                                               LineBreakMode="TailTruncation"/>
                                    </StackLayout>

                                    <Label Text="&#xf105;"
                                           FontFamily="FontAwesomeBold"
                                           TextColor="#ACACAC"
                                           FontSize="24"
                                           HorizontalOptions="EndAndExpand"
                                           VerticalOptions="CenterAndExpand">
                                        <Label.GestureRecognizers>
                                            <TapGestureRecognizer
                                                NumberOfTapsRequired="1"
                                                Command="{Binding Source={RelativeSource AncestorType={x:Type local:NotificacoesViewModel}},
                                                          Path=NotificacaoSelecionada}"
                                                CommandParameter="{Binding .}">
                                            </TapGestureRecognizer>
                                        </Label.GestureRecognizers>
                                    </Label>
                                </StackLayout>

                                <BoxView HeightRequest="1"
                                         BackgroundColor="#DDDDDD"
                                         Margin="0,5,0,5"/>
                            </StackLayout>
                        </DataTemplate>
                    </CollectionView.ItemTemplate>
                </CollectionView>

C#

ItemsListView.DataCadastroLabel.VerticalOptions

Answer 1

Define the view for the ItemTemplate in its own class and do it in that code-behind. Using x:Name on an inline DataTemplate doesn't make sense, because you are presumably creating several instances of the view.

Answer 2

Hello,

Welcome to our Microsoft Q&A platform!

You can try to create a Xamarin.Forms DataTemplateSelector to achieve this.

You can add a field(e.g. Status) to your binded item of CollectionView.

public class ItemModel  
{  
    // other field  

    public int Status { get; set; }  // Landscape and portrait  
}  

And create DataTemplateSelector like this:

public  class MyDataTemplateSelector:DataTemplateSelector  
{  

      public DataTemplate LandTemplate { get; set; }  

  public DataTemplate PortraitTemplate { get; set; }  

   protected override DataTemplate OnSelectTemplate(object item, BindableObject container)  
    {  
    return ((ItemModel)item).Status == 0 ? LandTemplate : PortraitTemplate;  
   }  
}  

When you switch between landscape and portrait, you can change the value of status in your ItemModel.

The program will select different templates( LandTemplate and PortraitTemplate) based on the value of status.

For more details, you can refer to the official sample : https://learn.microsoft.com/en-us/samples/xamarin/xamarin-forms-samples/templates-datatemplateselector/

Best Regards,

Jessie Zhang

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