MvvmCross MvxWindowsPage< TViewModel>编译错误 [英] MvvmCross MvxWindowsPage<TViewModel> compilation error

问题描述

我正在使用MvvmCross框架编写一个Xamarin.iOS，Xamarin.Android和UWP跨平台应用程序.

I am writing a Xamarin.iOS, Xamarin.Android and UWP cross-platform application with the MvvmCross framework.

我正在制作一个具有LoginViewModel的LoginPage.在Xamarin.iOS，Xamarin.Android项目中，ViewModel和下面的View的绑定工作正常

I am making a LoginPage which has a LoginViewModel. In the Xamarin.iOS, Xamarin.Android projects, the binding of the ViewModel and the View with below works just fine

public class LoginActivity : MvxAppCompatActivity<LoginViewModel> 

public partial class LoginViewController : MvxViewController<LoginViewModel>  

尝试在UWP项目上执行与上述相同的操作，但出现一些错误.

Trying to do the same as above on UWP project, I get some error.

在XAML中:

<views:MvxWindowsPage
x:TypeArguments="viewModels:LoginViewModel" x:Class="MyApp.UWP.Views.LoginView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:views="using:MvvmCross.WindowsUWP.Views"
xmlns:viewModels="using:MyApp.PresentationCore.ViewModels"
mc:Ignorable="d">

我的C#代码是

public sealed partial class LoginView : MvxWindowsPage<LoginViewModel>

但是我得到编译错误.我该如何解决?

But I get compilation errors. How can I resolve them?

• `元素"MvxWindowsPage"上的未知成员"TypeArguments"
• 名称空间"using:MyApp.PresentationCore.ViewModels"中不存在"LoginViewModel"名称.
• GenericArguments [0]，"MvvmCross.WindowsUWP.Views.MvxWindowsPage`1 [TViewModel]"上的"System.Object"违反了 类型为"TViewModel"的约束.

• `Unknown member 'TypeArguments' on element 'MvxWindowsPage'
• The name "LoginViewModel" does not exist in the namespace "using:MyApp.PresentationCore.ViewModels".
• GenericArguments[0], 'System.Object', on 'MvvmCross.WindowsUWP.Views.MvxWindowsPage`1[TViewModel]' violates the constraint of type 'TViewModel'.

我认为错误有点模棱两可，因为在第一个错误中没有模板版本，但是在第三个错误中则涉及到违反模板约束的情况.

I think the errors are a little ambiguous because at the first error there is no templated version, but the third error is about a template constraint violation.

我知道有一个将ViewModel和View与命名约定或属性绑定的选项，但是我想使用这种强类型的解决方案.

I know there is an option binding the ViewModel and the View with naming convention or attributes, but I would like to use this strongly typed solution.

推荐答案

不幸的是，我相信UWP不支持基本页面的TypeArguments以及随后的泛型类型参数.您可以在 Prism GitHub线程中进行讨论.因此，您将不得不使用其他注册选项之一.

Unfortunately I believe UWP does not support TypeArguments and subsequently generic types parameters for a base pages. You can check out the Prism GitHub thread where they discuss it. So you will have to go with one of the other registration options.

Mvvmcross提供了多种将View注册到ViewModel的替代方法.在Mvvmcross初始化期间，它将尝试使用ViewModel注册到您的View. cs#L31"rel =" nofollow> MvxViewModelViewTypeFinder 的顺序如下:

Mvvmcross offers various alternative approaches for registering your View to a ViewModel. During initialisation of Mvvmcross it will attempt to register your ViewModel to your View using MvxViewModelViewTypeFinder in the following order:

基于属性的注册:

Attribute based registration:

您可以在页面类中添加MvxViewFor属性.

You can add MvxViewFor attribute to your page class.

[MvxViewFor(typeof(FirstViewModel))]
public sealed partial class FirstView : MvxWindowsPage
{
    public FirstView()
    {
        this.InitializeComponent();
    }
}

基于具体类型的注册:

Concrete type based registration:

您可以通过指定ViewModel的具体类型将View注册到ViewModel.

You can register your View to your ViewModel by specifying the concrete type of the ViewModel.

public sealed partial class FirstView : MvxWindowsPage
{
    public new FirstViewModel ViewModel => base.ViewModel as FirstViewModel;

    public FirstView()
    {
        this.InitializeComponent();
    }
}

或者在可以使用通用基类的Android和iOS上:

Or in the case of Android and iOS where generic base class can be used:

// Android
public class FirstActivity : MvxAppCompatActivity<FirstViewModel>

// iOS
public class FirstViewController : MvxViewController<FirstViewModel>

基于公约的注册:

Convention based registration:

您可以让视图和ViewModel遵循相同的命名约定，Mvvmcross会为您映射它们(xxxView和xxxViewModel)

You can have your view and ViewModel follow the same naming convention and Mvvmcross will map them for you (xxxView and xxxViewModel)

查看

public sealed partial class FirstView : MvxWindowsPage
{
    public FirstView()
    {
        this.InitializeComponent();
    }
}

ViewModel

public class FirstViewModel : MvxViewModel

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