如何解决具有不同视图模型的同一视图上的 Xamarin 多重绑定上下文
我有一个带有 2 个不同 viewmodel（ContentPage、RSSFornecedores）的 RSSProdutos，但我在将它们绑定到同一个 ContentPage 时遇到了问题
我试图做这样的事情：
Multiple BindingContext's On Same ContentPage,Two different Views?
但由于以下错误而无法正常工作：
类型 'viewmodels:RSSProdutos' 像标记扩展一样使用，但不是从 MarkupExtension 派生的
如果我添加为 StaticResource BindingContext="{Binding Produto,Source = {StaticResource viewmodels:RSSProdutos}}" 我会收到错误：
未找到关键 staticviewmodels:RSSProdutos 的静态资源
Documentos.xaml：
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:viewmodels="clr-namespace:AppQ4evo.viewmodels"
xmlns:controls="clr-namespace:AppQ4evo.CSS"
x:Class="AppQ4evo.Views.Documentos"
BackgroundColor="White">
<ContentPage.BindingContext>
<viewmodels:RSSTerceiros />
</ContentPage.BindingContext>
<!--Common Styles Starts-->
<ContentPage.Resources>
<ResourceDictionary>
<Color x:Key="LightGreenColor">#2FA999</Color>
<Color x:Key="BorderColor">#D8D8D8</Color>
<Style x:Key="LableStyle" targettype="Label">
<Setter Property="TextColor" Value="#666666" />
<Setter Property="FontSize" Value="Large" />
</Style>
<Style x:Key="FrameStyle" targettype="Frame">
<Setter Property="HasShadow" Value="False" />
<Setter Property="Padding" Value="0" />
<Setter Property="CornerRadius" Value="5" />
<Setter Property="BorderColor" Value="{StaticResource BorderColor}" />
</Style>
<Style x:Key="EntryStyle" targettype="Entry">
<Setter Property="HeightRequest" Value="40"></Setter>
<Setter Property="Margin" Value="5,0"></Setter>
</Style>
</ResourceDictionary>
</ContentPage.Resources>
<!--Common Styles Ends-->
<ContentPage.toolbaritems>
<ToolbarItem x:Name="iconAttach" Text="Documentos" Order="Primary" Icon="attach.png" Priority="-1" Clicked="Button_Clicked_AnexosAsync" />
</ContentPage.toolbaritems>
<NavigationPage.TitleView>
<StackLayout Orientation="Horizontal" VerticalOptions="Center" HorizontalOptions="Center">
<Label Text="Documentos" FontSize="18" FontAttributes="Bold" TextColor="White" VerticalTextAlignment="Center" />
</StackLayout>
</NavigationPage.TitleView>
<ContentPage.Content>
<AbsoluteLayout Padding="0" VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand">
<StackLayout>
<Grid x:Name="docs" Padding="-2">
<Grid.RowDeFinitions>
<RowDeFinition Height="Auto"/>
<RowDeFinition Height="Auto"/>
<RowDeFinition Height="Auto"/>
<RowDeFinition Height="Auto"/>
</Grid.RowDeFinitions>
<StackLayout Grid.Row="0" Margin="10,20">
<Grid>
<Grid.ColumnDeFinitions>
<ColumnDeFinition Width="360" />
<ColumnDeFinition Width="*" />
</Grid.ColumnDeFinitions>
<Frame Style="{StaticResource FrameStyle}">
<controls:CustomEntry x:Name="DataDocEntry" Grid.Column="0" Text="{Binding Date,StringFormat='{0:MMMM dd,yyyy}',Source={x:Reference MainDatePicker}}" IsEnabled="false" Style="{StaticResource EntryStyle}" />
</Frame>
<DatePicker x:Name="MainDatePicker" Grid.Column="1" MinimumDate="1/1/2018" MaximumDate="12/31/2030" HeightRequest="30" BackgroundColor="Gray" Opacity="0" />
<Image VerticalOptions="Center" Grid.Column="1" HorizontalOptions="End" Source="icalendar.png" HeightRequest="30" WidthRequest="30">
<Image.GestureRecognizers>
<TapGestureRecognizer Tapped="Calendario_Clicked" NumberOfTapsrequired="1" />
</Image.GestureRecognizers>
</Image>
</Grid>
<Frame Style="{StaticResource FrameStyle}">
<controls:CustomEntry x:Name="NumExternoEntry" Placeholder="Número Externo" Keyboard="Numeric" />
</Frame>
<Frame Style="{StaticResource FrameStyle}">
<controls:CustomPicker x:Name="FornecedorEntry" Title="Selecionar Fornecedor" />
</Frame>
</StackLayout>
<StackLayout Grid.Row="1" Margin="0,-10">
<Button x:Name="btnAdd" Text="Adicionar" Clicked="btnAddPopup_Clicked" />
</StackLayout>
<Grid x:Name="ListViewHeaders" Grid.Row="2" Margin="0,20,0">
<Grid.RowDeFinitions>
<RowDeFinition Height="40"/>
<RowDeFinition Height="Auto"/>
</Grid.RowDeFinitions>
<Grid.ColumnDeFinitions>
<ColumnDeFinition Width="*"/>
<ColumnDeFinition Width="60" />
<ColumnDeFinition Width="65" />
<ColumnDeFinition Width="80" />
<ColumnDeFinition Width="25" />
<ColumnDeFinition Width="60" />
</Grid.ColumnDeFinitions>
<BoxView Color="Black" Grid.Row="0" Grid.ColumnSpan="8" HeightRequest="0.5" />
<BoxView Color="DimGray" Grid.Row="0" Grid.ColumnSpan="8" />
<Label Grid.Column="1" Text="Produto" XAlign="Center" YAlign="Center" TextColor="White" FontAttributes="Bold" FontSize="Small"/>
<Label Grid.Column="2" Text="Descrição" XAlign="Center" YAlign="Center" TextColor="White" FontAttributes="Bold" FontSize="Small"/>
<Label Grid.Column="3" Text="Observação" XAlign="Center" YAlign="Center" TextColor="White" FontAttributes="Bold" FontSize="Small"/>
<Label Grid.Column="4" Text="Qtd" XAlign="Center" YAlign="Center" TextColor="White" FontAttributes="Bold" FontSize="Small"/>
<Label Grid.Column="5" Text="Valor Unitário" XAlign="Center" YAlign="Center" TextColor="White" FontAttributes="Bold" FontSize="Small"/>
<Label Grid.Column="6" Text="IVA" XAlign="Center" YAlign="Center" TextColor="White" FontAttributes="Bold" FontSize="Small"/>
</Grid>
<ListView x:Name="DocumentsList" ItemsSource="{Binding DocumentsList,Source = {viewmodels:RSSProdutos}}" Grid.Row="2" HasUnevenRows="True" Margin="0,60" BackgroundColor="White">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<ViewCell.View>
<Grid>
<Grid.RowDeFinitions>
<RowDeFinition Height="30"></RowDeFinition>
</Grid.RowDeFinitions>
<Grid.ColumnDeFinitions>
<ColumnDeFinition Width="30"></ColumnDeFinition>
<ColumnDeFinition Width="50"></ColumnDeFinition>
<ColumnDeFinition Width="70"></ColumnDeFinition>
<ColumnDeFinition Width="80"></ColumnDeFinition>
<ColumnDeFinition Width="30"></ColumnDeFinition>
<ColumnDeFinition Width="50"></ColumnDeFinition>
<ColumnDeFinition Width="45"></ColumnDeFinition>
</Grid.ColumnDeFinitions>
<Label x:Name="ProdutoLabel" Grid.Row="0" Grid.Column="1" BindingContext="{Binding Produto,Source = {viewmodels:RSSProdutos}}" Text="{Binding Produto}" XAlign="Center" YAlign="Center" TextColor="Black" FontAttributes="Bold"/>
<!--<Label Grid.Row="0" Grid.Column="2" Text="{Binding Descricao}" XAlign="Center" YAlign="Center" TextColor="Black" FontAttributes="Bold"/>
<Label Grid.Row="0" Grid.Column="3" Text="{Binding Observacao}" XAlign="Center" YAlign="Center" TextColor="Black" FontAttributes="Bold"/>
<Label Grid.Row="0" Grid.Column="4" Text="{Binding Quantidade}" XAlign="Center" YAlign="Center" TextColor="Black" FontAttributes="Bold"/>
<Label Grid.Row="0" Grid.Column="5" Text="{Binding ValorUnitario}" XAlign="Center" YAlign="Center" TextColor="Black" FontAttributes="Bold"/>
<Label Grid.Row="0" Grid.Column="6" Text="{Binding Iva}" XAlign="Center" YAlign="Center" TextColor="Black" FontAttributes="Bold"/>-->
</Grid>
</ViewCell.View>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</Grid>
</StackLayout>
<ContentView x:Name="popupAddDocumentView" Margin="40,120" Padding="10,0" IsVisible="false">
<StackLayout VerticalOptions="Center" HorizontalOptions="Center">
<StackLayout Orientation="Vertical" HeightRequest="400" WidthRequest="300" BackgroundColor="Gray">
<Image HorizontalOptions="End" Source="close.png" HeightRequest="20" WidthRequest="20">
<Image.GestureRecognizers>
<TapGestureRecognizer Tapped="OnImageNaMetapped_ClosePopup" NumberOfTapsrequired="1" />
</Image.GestureRecognizers>
</Image>
<Entry x:Name="ProdutoEntry" Margin="20,0" Placeholder="Produto" />
<Entry x:Name="DescricaoEntry" Margin="20,0" Placeholder="Descrição" />
<Entry x:Name="ObservacaoEntry" Margin="20,0" Placeholder="Observação" />
<Entry x:Name="QuantidadeEntry" Margin="20,0" Placeholder="Quantidade" />
<Entry x:Name="ValorUnitarioEntry" Margin="20,0" Placeholder="Valor" />
<Entry x:Name="IvaEntry" Margin="20,0" Placeholder="IVA" />
<Button x:Name="btnAddDocument" Margin="20,0" Clicked="btnAddDocument_Clicked" Text="Adicionar" />
</StackLayout>
</StackLayout>
</ContentView>
</AbsoluteLayout>
</ContentPage.Content>
</ContentPage>
最好的问候
解决方法
- 如果您的代码中还没有它的实例，则需要通过给它一个键来创建
RssProdutos的实例作为 xaml 中的资源：
<ContentPage.Resources>
<viewModels:RssProdutos x:Key="RssProdutos "/>
</ContentPage.Resources>
...
<ListView x:Name="DocumentsList" ItemsSource="{Binding DocumentsList,Source={StaticResource RssProdutos}}"
Grid.Row="2" HasUnevenRows="True" Margin="0,60" BackgroundColor="White">
- 如果您的代码隐藏（属性）中已经有
RssProdutos的实例，则无需添加另一个作为静态资源的实例，您只需绑定到它即可：
RssProdutos RssProdutosVm {get; set;} = new RssProdutos();
<ContentPage x:Name="thispage"
...
>
...
<ListView x:Name="DocumentsList" ItemsSource="{Binding DocumentsList,Source={Binding Source={x:Reference thispage},Path=RssProdutosVm}}"
Grid.Row="2" HasUnevenRows="True" Margin="0,60" BackgroundColor="White">
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