【发布时间】：2017-04-04 20:15:43
【问题描述】：
我一直在尝试使用层次结构和导航来遵循这个 MVVM 教程：
https://www.tutorialspoint.com/mvvm/mvvm_hierarchies_and_navigation.htm
到目前为止，我已经完成了本教程的大部分内容，但是对于 UWP，隐式绑定似乎不适用于 UWP，因此我无法复制本教程，因为即使我使用了 x:DataType使用 x:Key 编译器要求 x:key 属性以便将视图与视图模型绑定，我得到的只是我的视图模型的全名，而不是能够看到实际内容。
那么有人可以帮助我如何在 UWP 中使用普通 MVVM 模式在没有 MVVM Light 或 MVVM Cross 等工具的帮助下正确使用层次结构。
我将把目前用于 UWP 应用的代码留给你：
<Page
x:Class="MVVMHeirarchiesDemo.MainPageView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:MVVMHeirarchiesDemo"
xmlns:views="using:MVVMHeirarchiesDemo.Views"
xmlns:viewmodel="using:MVVMHeirarchiesDemo.ViewModel"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<!--Anytime the current view model is set to an instance of a CustomerListViewModel,
it will render out a CustomerListView with the ViewModel is hooked up. It’s an order ViewModel,
it'll render out OrderView and so on.
We now need a ViewModel that has a CurrentViewModel property and some logic and commanding
to be able to switch the current reference of ViewModel inside the property.-->
<Page.DataContext>
<viewmodel:MainPageViewModel/>
</Page.DataContext>
<Page.Resources>
<DataTemplate x:Key="CustomerTemplate" x:DataType="viewmodel:CustomerListViewModel">
<views:CustomerListView/>
</DataTemplate>
<DataTemplate x:Key="OrderTemplate" x:DataType="viewmodel:OrderViewModel">
<views:OrderView/>
</DataTemplate>
</Page.Resources>
<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid x:Name="NavBar"
Grid.Row="0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Button Content="Customers"
Command="{Binding NavCommand}"
CommandParameter="customers"
Grid.Column="0"
Grid.Row="0"/>
<Button Content="Orders"
Command="{Binding NavCommand}"
CommandParameter="orders"
Grid.Column="2"
Grid.Row="0"/>
</Grid>
<Grid x:Name="MainContent"
Grid.Row="1">
<ContentControl Content="{Binding CurrentViewModel}"/>
</Grid>
</Grid>
如您所见，主要问题可能出在我的主页上。资源我猜我的绑定在
因为那行代码无法访问我的视图的实际内容。
这是我的主视图的视图模型：
namespace MVVMHeirarchiesDemo.ViewModel
{
/*Derive all of your ViewModels from BindableBase class.*/
public class MainPageViewModel : BindableBase
{
public MainPageViewModel()
{
NavCommand = new MyCommand<string>(OnNavigation);
}
private CustomerListViewModel _customerListViewModel = new CustomerListViewModel();
private OrderViewModel _orderViewModel = new OrderViewModel();
private BindableBase _currentViewModel;
public BindableBase CurrentViewModel
{
get
{
return _currentViewModel;
}
set
{
SetProperty(ref _currentViewModel, value);
}
}
public MyCommand<string> NavCommand { get; private set; }
private void OnNavigation(string destination)
{
switch (destination)
{
case "orders":
{
CurrentViewModel = _orderViewModel;
break;
}
case "customers":
default:
CurrentViewModel = _customerListViewModel;
break;
}
}
}
}
最后这是我的辅助可绑定类：
namespace MVVMHeirarchiesDemo
{
/*The main idea behind this class is to encapsulate the INotifyPropertyChanged implementation
* and provide helper methods to the derived class so that they can easily trigger the appropriate notifications.
* Following is the implementation of BindableBase class.*/
public class BindableBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged = delegate { };
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
protected virtual void SetProperty<T>(ref T member, T val, [CallerMemberName]string propertyName = null)
{
if (object.Equals(member, val))
return;
member = val;
OnPropertyChanged(propertyName);
}
}
}
我希望有人能帮我解决这个问题。
【问题讨论】：
-
为了在 UWP 中工作，我想您需要在
ContentTemplateSelector元素的ContentTemplateSelector属性中实现DataTemplateSelector，因为您正在学习 WPF 教程。请记住，并非 WPF 中的每个 XAML 逻辑 都只能在 UWP 中工作。 -
是的，我刚刚发现了一个 DataTemplateSelector 问题，我现在就应用它。谢啦！！！这是在 UWP 中解决此问题的正确方法。