MvvmCross、UWP、MessengerPlugin：加载页面失败

Question

问题是：当我将IMvxMessanger的构造函数DI添加到ViewModel时，我得到了一个错误：“无法加载页面”；如果我删除这个 DI，我的工具就可以正常工作。顺便说一句，IHelloService 不会给出这个错误，它只工作正常 w/o IMvxMessanger.

我遵循了本手册：https://mvvmcross.com/docs/a-windows-universal-app-platform-project

MvvmCross 版本：4.4.0

代码示例：

FirstViewModel

public class FirstViewModel : MvxViewModel
{
    private readonly IHelloService _helloService;
    private readonly IMvxMessenger _messenger;

    public FirstViewModel(IHelloService helloService, IMvxMessenger messenger)
    {
        _helloService = helloService;
        _messenger = messenger;
    }

    private string _hello = "Hello MvvmCross";
    public string Hello
    {
        get { return _hello; }
        set { SetProperty(ref _hello, value); }
    }
}

FirstView.xaml.cs

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

FirstView.xaml

<views:MvxWindowsPage
x:Class="MvvmCrossDocs.UWP.Views.FirstView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:MvvmCrossDocs.UWP.Views"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:views="using:MvvmCross.WindowsUWP.Views"
mc:Ignorable="d">

<Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
    <StackPanel>
        <TextBox Text="{Binding Hello, Mode=TwoWay}" />
        <TextBlock Text="{Binding Hello}" />
    </StackPanel>
</Grid>

设置

public class Setup : MvxWindowsSetup
{
    public Setup(Frame rootFrame) : base(rootFrame)
    {
    }

    protected override IMvxApplication CreateApp()
    {
        return new Core.App();
    }
}

App.xaml.cs

中也有这一行

if (rootFrame.Content == null)
{
    var setup = new Setup(rootFrame);
    setup.Initialize();

    var start = Mvx.Resolve<IMvxAppStart>();
    start.Start();
}

Answer 1

我认为问题在于您在 UWP 项目中缺少 MvxMessenger 的 bootstrap class。 UWP 使用 Nuget 3 引入的 project.json 模板。目前，当您安装 nuget 包时，它们不允许将附加文件添加到您的项目中。

解决方法是手动添加bootstrap文件夹和相关插件bootstrap.cs文件，或者您可以在Setup.cs.[=17中注册插件的接口和实现=]

Bootstrap 方法：

创建 MessengerPluginBootstrap.cs

using MvvmCross.Platform.Plugins;

namespace <<YOUR_NAMESSPACE>>.Bootstrap
{
    public class MessengerPluginBootstrap
            : MvxPluginBootstrapAction<MvvmCross.Plugins.Messenger.PluginLoader>
    {
    }
}

Setup.cs 方法：

针对 MvxMessengerHub 实现注册 IMvxMessenger 的接口。

protected override void InitializeLastChance()
{
    base.InitializeLastChance();
    Mvx.RegisterSingleton<IMvxMessenger>(new MvxMessengerHub());
}

MvvmCross、UWP、MessengerPlugin：加载页面失败

MvvmCross, UWP, MessengerPlugin: Failed to load Page

c#

mvvmcross

xamarin.uwp