在过去的几个星期，我一直在致力于开发使用MVVMCross框架，一个跨平台的应用程序（IOS /安卓/ WP7）的。今天，我遇到了一个问题，我真的不知道该怎么解决，所以希望你可以把我在正确的方向。

For the past couple of weeks I've been working on developing a cross platform app (IOS/Android/WP7) using the MVVMCross framework. Today I ran into a problem I don't really know how to solve, so hopefully you can push me in the right direction.

在IOS我有以下建设导航到另一个页面（在code以下坐落在一个视图模型）：

In the IOS I have the following construction for navigating to another page (the code below is located in a ViewModel):

KeyValuePair<string,string> kvpAct1 = new KeyValuePair<string, string>("short", ".countertest5");

public IMvxCommand BeckhoffActuator1
{
    get
    {           
        return new MvxRelayCommand<Type>((type) => this.RequestNavigate<Beckhoff.BeckhoffActuatorViewModel>(kvpAct1));
    }
}

在此IMvxCommand被触发（按钮pressed）下一个视图被加载，在这种情况下，BeckhoffActuatorViewModel。在BeckhoffActuatorView的code我用的是keyvaluepair从上面的：

When this IMvxCommand is fired (button pressed) the next View is loaded, in this case the BeckhoffActuatorViewModel. In the code of the BeckhoffActuatorView I use the keyvaluepair from above:

public class BeckhoffActuatorView : MvxTouchDialogViewController<BeckhoffActuatorViewModel>
{

    ICollection<string> icol;

    public BeckhoffActuatorView(MvxShowViewModelRequest request) : base(request, UITableViewStyle.Grouped, null, true)
    {

        icol = request.ParameterValues.Values;

    }

    public override void ViewDidLoad()
    {
        //Code
    }
}

此建设工作正常的IOS，但我想用同样的结构在我的Andr​​oid应用程序。

This construction is working fine in IOS, but I would like to use the same construction in my android App.

在code。在视图模型并没有改变，因为这是MVVM的整体思路。但BackhoffActuatorView的code是不同的Andr​​oid版本：

The code in the ViewModel hasn't changed since that's the whole idea of MVVM. But the code of the BackhoffActuatorView is different for Android:

public class BeckhoffActuatorView : MvxBindingActivityView<BeckhoffSensorViewModel>
{
    public ICollection<string> icol;

    public BeckhoffActuatorView()
    {
        Debug.WriteLine("Standard");
    }

    public BeckhoffActuatorView(MvxShowViewModelRequest request)
    {
        Debug.WriteLine("Custom");

        icol = request.ParameterValues.Values;
    }

    protected override void OnViewModelSet()
    {

        SetContentView(Resource.Layout.BeckhoffActuatorView);

    }
}

在code以上不工作时，MvxBindingActivityView似乎并没有实施类似的ViewController我在IOS使用的东西。在code只能来自于标准的构造函数，当我离开，一出完全不会编译/运行。

The code above isn't working, the MvxBindingActivityView doesn't seem to implement something similar to the ViewController I use in IOS. The code only come in the standard constructor, and when I leave that one out completely it won't compile/run.

有谁知道知道，我可以访问我送的RequestNavigate的keyvaluepair？谢谢！

Does anyone know know I can access the keyvaluepair I send with the RequestNavigate? Thank you!

推荐答案

MVVMCross是基于非常习惯 - 和它的作品上的ViewModels之间传递消息尽可能的想法

MVVMCross is very convention based - and it works on the idea of passing messages between ViewModels wherever possible.

如果您在使用导航到一个视图模型：

If you navigate to a ViewModel using:

KeyValuePair<string,string> kvpAct1 = new KeyValuePair<string, string>("short", ".countertest5");

public IMvxCommand BeckhoffActuator1
{
    get
    {           
        return new MvxRelayCommand<Type>((type) => this.RequestNavigate<Beckhoff.BeckhoffActuatorViewModel>(kvpAct1));
    }
}

那么你应该能够使用构造来挑选了在BeckhoffActuatorViewModel：

then you should be able to pick that up in the BeckhoffActuatorViewModel using the constructor:

public class BeckhoffActuatorViewModel : MvxViewModel
{
    public BeckhoffActuatorViewModel(string short)
    {
        ShortValue = short;
    }

    private string _shortValue;
    public string ShortValue
    {
        get
        {
            return _shortValue;
        }
        set
        {
            _shortValue = value;
            FirePropertyChanged("ShortValue");
        }
    }
}

和你的意见就可以访问 ViewModel.ShortValue （适用于iOS这可以base.ViewDidLoad（后进行），为Android的OnCreate（后）和WP7后的OnNavigatedTo ）

And your views can then access ViewModel.ShortValue (for iOS this can be done after base.ViewDidLoad(), for Android after OnCreate() and for WP7 after OnNavigatedTo)

有关这方面的一个例子，看看在TwitterSearch例如：

For an example of this, take a look at the TwitterSearch example:

这有HomeViewModel使用它调用导航：

This has a HomeViewModel which calls navigate using:

    private void DoSearch()
    {
        RequestNavigate<TwitterViewModel>(new { searchTerm = SearchText });
    }

和一个TwitterViewModel接收使用构造的搜索关键词：

and a TwitterViewModel which receives the searchTerm using the constructor:

    public TwitterViewModel(string searchTerm)
    {
        StartSearch(searchTerm);
    }

请注意，只有字符串，则允许此消息传递在present中 - 但可以使用JSON.Net一直连载自己的对象 - 或者您也可以扩展框架 - 它是开源

Please note that only strings are allowed in this message passing at present - but you can always serialise your own objects using JSON.Net - or you can extend the framework - it's open source.

请注意，只有字符串 S， INT S，双和布尔，则允许在这个构造函数的参数传递在present - 这是由于XAML的URL和Android的意图系列化的要求。如果你想用你自己的自定义序列化对象与导航试验，然后请参阅的http://slodge.blogspot.co.uk/2013/01/navigating-between-viewmodels-by-more.html.

Please note that only strings, ints, doubles and bools are allowed in this constructor parameter passing at present - this is due to serialisation requirements for Xaml Urls and for Android Intents. If you want to experiment with navigation using your own custom serialised objects, then please see http://slodge.blogspot.co.uk/2013/01/navigating-between-viewmodels-by-more.html.

另外，注意，如果你想使用匿名对象导航（ RequestNavigate＆LT; TwitterViewModel＆GT;（新{搜索关键词= SearchText}）; ），那么你就需要做确保了 InternalsVisibleTo 属性设置 - 见https://github.com/slodge/MvvmCrossTwitterSearch/blob/master/TwitterSearch.Core/Properties/AssemblyInfo.cs:

Also, note that if you want to use the anonymous object navigation (RequestNavigate<TwitterViewModel>(new { searchTerm = SearchText });) then you will need to make sure that an InternalsVisibleTo attribute is set - see https://github.com/slodge/MvvmCrossTwitterSearch/blob/master/TwitterSearch.Core/Properties/AssemblyInfo.cs:

[assembly: InternalsVisibleTo("Cirrious.MvvmCross")]

另外...不适合胆小的人......这不是好MVVM code......但是，如果你真的想/需要访问一个Android活动内部的MvxShowViewModelRequest数据，然后你可以从收到的意向提取出来 - 有包含请求（见 CreateViewModelFromIntent 的deserialisation在https://github.com/slodge/MvvmCross/blob/master/Cirrious/Cirrious.MvvmCross/Android/Views/MvxAndroidViewsContainer.cs)

Further... not for the faint-hearted... and this isn't "good mvvm code"... but if you really want/need to access the MvxShowViewModelRequest data inside an Android activity, then you can extract it from the incoming Intent - there's an Extras string containing the request (see the deserialisation in CreateViewModelFromIntent in https://github.com/slodge/MvvmCross/blob/master/Cirrious/Cirrious.MvvmCross/Android/Views/MvxAndroidViewsContainer.cs)