[英]How do I use ViewModelViewHost in a ListView ItemTemplate with ReactiveUI and Xamarin Forms?
我正在尝试将ReactiveUI与Xamarin Forms一起使用,并且在使View Model Location在具有ItemTemplate的ListView中工作时遇到了一些困难。
我已经使用以下行在AppBootstrapper.cs中注册了View和ViewModel:
Locator.CurrentMutable.Register(() =>
new MonkeyCellView(), typeof(IViewFor<MonkeyCellViewModel>));
我还引用了XAML中的ReactiveUI.XamForms
命名空间,并将ViewModelViewHost
包裹在Page
元素中:
<?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="XamarinFormsReactiveListView.Views.MonkeyListView"
xmlns:rui="clr-namespace:ReactiveUI.XamForms;assembly=ReactiveUI.XamForms">
<StackLayout>
<Button x:Name="AddMonkey" Text="Add Monkey"/>
<ListView ItemsSource="{Binding Monkeys}" x:Name="MonkeyList">
<ListView.ItemTemplate>
<DataTemplate>
<Page>
<rui:ViewModelViewHost x:Name="vmvh" ViewModel="{Binding .}" />
</Page>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackLayout>
注意:您必须将ViewModelViewHost包裹在Page元素中,因为根据该文件,这是ReactiveUI当时使用Xamarin Forms for ViewModelViewHost的ReactiveUI支持的唯一元素,如下所示:
当我运行XamarinFormsReactiveListView.iOS项目时,在System.Reflection.TargetInvocationException的InnerException中收到以下错误消息:
不知道如何检测何时激活/停用ReactiveUI.XamForms.ViewModelViewHost,您可能需要实现IActivationForViewFetcher
原来我有点不对劲,应该在DataTemplate内部引用我自己的类MonkeyCellView : ViewCell, IViewFor<MonkeyCellViewModel>
,并使用<views:MonkeyCellView ViewModel="{Binding .}"/>
将其ViewModel绑定到当前项<views:MonkeyCellView ViewModel="{Binding .}"/>
:
<?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="XamarinFormsReactiveListView.Views.MonkeyListView"
xmlns:views="clr-namespace:XamarinFormsReactiveListView.Views;assembly=XamarinFormsReactiveListView">
<StackLayout>
<Button x:Name="AddMonkey" Text="Add Monkey"/>
<ListView ItemsSource="{Binding Monkeys}" x:Name="MonkeyList">
<ListView.ItemTemplate>
<DataTemplate>
<views:MonkeyCellView ViewModel="{Binding .}"/>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackLayout>
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