在 MenuItem 上使用 DataTrigger 在 Xamarin.Forms 中显示不同的状态

Question

我正在尝试在 Xamarin.Forms 中的 ViewCell 内的 MenuItem 上使用 DataTrigger。 ListView 显示对话列表。如果对话被删除，我希望菜单项显示 "Restore"。如果对话没有被删除，我想显示"Delete"。

构建时出现错误：

Error: Position 12:49. Can't resolve Clicked on MenuItem

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="EventingVolunteers.MailboxBoxPage" Title="Mailbox - Box">
    <ContentPage.Content>
        <AbsoluteLayout x:Name="absLayout" VerticalOptions="FillAndExpand">
            <ListView x:Name="listView" HasUnevenRows="true" ItemSelected="OnItemSelected" HeightRequest="{Binding Path=Height, Source={x:Reference absLayout}}">
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <ViewCell>
                            <ViewCell.ContextActions>
                                <MenuItem CommandParameter="{Binding Id}">
                                    <DataTrigger TargetType="MenuItem" Binding="{Binding Is_Deleted}" Value="false">
                                        <Setter Property="Clicked" Value="OnDelete" />
                                        <Setter Property="Text" Value="Delete" />
                                        <Setter Property="IsDestructive" Value="True" />
                                        <Setter Property="Icon" Value="ic_delete.png" />
                                    </DataTrigger>
                                    <DataTrigger TargetType="MenuItem" Binding="{Binding Is_Deleted}" Value="true">
                                        <Setter Property="Clicked" Value="OnRestore" />
                                        <Setter Property="Text" Value="Restore" />
                                        <Setter Property="IsDestructive" Value="False" />
                                        <Setter Property="Icon" Value="" />
                                    </DataTrigger>
                                </MenuItem>
                            </ViewCell.ContextActions>
                            <StackLayout Orientation="Horizontal" BackgroundColor="White" Padding="10,10,10,10">
                                <StackLayout Spacing="0" Orientation="Horizontal" HorizontalOptions="StartAndExpand">
                                    <StackLayout Orientation="Vertical">
                                        <StackLayout HorizontalOptions="StartAndExpand" Orientation="Horizontal">
                                            <Label Text="{Binding Subject}" VerticalTextAlignment="Center" FontAttributes="Bold">
                                                <Label.Triggers>
                                                    <DataTrigger TargetType="Label" Binding="{Binding Is_Unread}" Value="true">
                                                        <Setter Property="TextColor" Value="#337ab7" />
                                                    </DataTrigger>
                                                </Label.Triggers>
                                            </Label>
                                        </StackLayout>
                                        <StackLayout HorizontalOptions="StartAndExpand" Orientation="Horizontal">
                                            <Label Text="{Binding Participant}" VerticalTextAlignment="Center" />
                                        </StackLayout>
                                        <StackLayout HorizontalOptions="StartAndExpand" Orientation="Horizontal">
                                            <Label Text="{Binding Last_Message_At}" VerticalTextAlignment="Center" />
                                        </StackLayout>
                                    </StackLayout>
                                </StackLayout>
                            </StackLayout>
                        </ViewCell>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>
            <ContentView x:Name="overlay" AbsoluteLayout.LayoutBounds="0, 0, 1, 1"  AbsoluteLayout.LayoutFlags="All" IsVisible="True" BackgroundColor="#C0808080" Padding="10, 0">
                <ActivityIndicator  WidthRequest="110" HeightRequest="70" IsRunning="True" IsVisible="True" Color="Black" HorizontalOptions="CenterAndExpand" VerticalOptions="CenterAndExpand"/>
            </ContentView>
        </AbsoluteLayout>
    </ContentPage.Content>
</ContentPage>

Answer 1

您的问题与此行有关：

<Setter Property="Clicked" Value="OnDelete" />

删除此行 - MenuItem 没有 Clicked 属性。 Clicked 是一个事件。

您应该绑定到 MenuItem 标签中的 Clicked 事件，例如：

<MenuItem CommandParameter="{Binding Id}" Command="{Binding OnDelete}">

在 MenuItem 上使用 DataTrigger 在 Xamarin.Forms 中显示不同的状态

Using DataTrigger on MenuItem to display different state in Xamarin.Forms

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