c# – MvvmCross,UWP,MessengerPlugin：无法加载页面

问题是：当我将IMvxMessanger的构造函数DI添加到viewmodel时出现错误：“无法加载页面”;如果我将删除此DI,我的工具工作正常.顺便说一下,IHelloService不会给出这个错误,只有没有IMvxMessanger才能正常工作.

我遵循了这本手册：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>

建立

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

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

这也是App.xaml.cs中的这一行

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

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

解决方法

我相信问题是你在UWP项目中缺少MvxMessenger的bootstrap类. UWP使用Nuget 3引入的project.json模板.目前,当您安装nuget包时,不允许向项目添加附加文件.

解决方法是手动添加bootstrap文件夹和相关的插件bootstrap.cs文件,或者您可以在Setup.cs中注册插件的界面和实现.

引导方法：

创建一个MessengerPluginBootstrap.cs

using MvvmCross.Platform.Plugins;

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

Setup.cs方法：

根据MvxMessengerHub实现注册IMvxMessenger的接口.

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