如何绑定到视图模型而不是页面 [英] How to bind to a viewmodel instead of a page

问题描述

我的问题是viewcell，因为它是IssueModel类，所以找不到OnDelete命令，我试图更改Listview的绑定上下文，但是除了上述绑定之外，它没有任何改变.

My problem is with the viewcell, the OnDelete command is not found due to it being of the IssueModel class, I've attempted to change the binding-context of the Listview, but that doesn't change anything except the above binding.

是否有任何方法可以更改视单元的绑定上下文，所以我不必将命令放入IssueModel中?我尝试了以下解决方案，但出现错误

Is there any way to change the binding context of the viewcell so I don't have to put the command into to IssueModel? I've attempted the below solution but I get an error

无效的标记扩展名:预期类型为对象，实际类型为Issuepagemodel"

"Invalid markup extension: expected type is object, actual type is Issuepagemodel"

      xmlns:pageModels="clr-namespace:ASFT.PageModels;assembly=ASFT"

 <ListView ItemsSource="{Binding Issues}" SeparatorColor="#444444" RowHeight="90" IsPullToRefreshEnabled="True" IsRefreshing="{Binding IsBusy}" RefreshCommand="{Binding PullRefreshCommand}" >
        <ListView.Behaviors>
        <helperMethods:EventToCommandBehavior EventName="ItemSelected" 
                                          Command="{Binding OnSelectedIssueCommand}" 
                                          Converter="{StaticResource SelectedItemConverter}" />
        </ListView.Behaviors>
        <ListView.ItemTemplate>
            <DataTemplate>
                <ViewCell x:Name="Stalin">
                    <ViewCell.ContextActions>
                        <MenuItem x:Name="Hitler" Command="{Binding Path=BindingContext.OnDelete, Source={pageModels:IssueListPageModel}}" Text="Delete" IsDestructive="True" />
                    </ViewCell.ContextActions>

                    <ViewCell.View>
                        <Grid>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="Auto"></RowDefinition>
                                <RowDefinition Height="Auto"></RowDefinition>
                                <RowDefinition Height="*"></RowDefinition>
                            </Grid.RowDefinitions>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="70"></ColumnDefinition>
                                <ColumnDefinition Width="*"></ColumnDefinition>
                                <ColumnDefinition Width="50"></ColumnDefinition>
                            </Grid.ColumnDefinitions>

                            <Image Grid.Row="0" Grid.RowSpan="3" Grid.Column="0" Source="{Binding SeverityImagePath}" HorizontalOptions="Center" VerticalOptions="Center" HeightRequest="70"/>
                            <Image Grid.Row="0" Grid.RowSpan="3" Grid.Column="2" Source="{Binding StatusImagePath}" HorizontalOptions="Center" VerticalOptions="Center" HeightRequest="60"/>

                            <Label Grid.Row="0" Grid.Column="1" Text="{Binding Title}" LineBreakMode="TailTruncation" YAlign="Center" VerticalOptions="Start" Font="Bold, Medium"/>
                            <Label Grid.Row="1" Grid.Column="1" Text="{Binding Created, Converter={StaticResource DateToTextConverter}}" YAlign="Center" VerticalOptions="Start" Font="Medium"/>
                            <Label Grid.Row="2" Grid.Column="1" Text="{Binding Description}" LineBreakMode="WordWrap" YAlign="Start" VerticalOptions="Start" Font="Small"/>
                        </Grid>

                    </ViewCell.View>
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>

推荐答案

如果我理解您的问题，那应该很容易.

Should be quite easy, if I understand your problem.

将页面的BindingContext设置为包含Command且其下一个名为"MyRootLevelCommand"的ViewModel.

Set your page's BindingContext to your ViewModel that contains a Command with the next name "MyRootLevelCommand".

命名您的根UI元素:

<Grid x:Name="root"> .. </Grid>

让我们假设在此Grid中，您有一个ListView，并且想要将Command从页面视图模型绑定到ListView中的每个项目:

Let's assume that within this Grid you have a ListView and you want to bind a Command from the page viewmodel to each item in the ListView:

 <ListView.ItemTemplate>
    <DataTemplate>
        <ViewCell>
            <Button Command="{Binding Source={x:Reference root}, Path=BindingContext.MyRootLevelCommand}" />
        </ViewCell>
    </DataTemplate>
</ListView.ItemTemplate>

这篇关于如何绑定到视图模型而不是页面的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！