Prism Xamarin Forms导航服务DependencyService [英] Prism Xamarin Forms Navigation service, DependencyService

问题描述

正如棱镜所说，

要在您的ViewModels中获得INavigationService，只需索要它 作为构造函数参数

To obtain the INavigationService in your ViewModels simply ask for it as a constructor parameter

https://prismlibrary .github.io/docs/xamarin-forms/Navigation-Service.html#getting-the-navigation-service

像这样:

public SpeakPageViewModel(INavigationService navigationService) : base(navigationService)

{

_navigationService = navigationService;

}

我想将ITextToSpeech接口用作Prism示例:

and I want to use ITextToSpeech interface as Prism sample :

public MainPageViewModel(ITextToSpeech textToSpeech)
{
    _textToSpeech = textToSpeech;
    SpeakCommand = new DelegateCommand(Speak);
}

https://prismlibrary.github .io/docs/xamarin-forms/Dependency-Service.html#use-the-service

问题是:在向构造函数添加另一个参数时，导航不起作用.

The problem is: when add another parameter to the constructor, the navigation doesn't work.

public SpeakPageViewModel(ITextToSpeech textToSpeech, INavigationService navigationService) : base(navigationService)
        {
            _navigationService = navigationService;
            _textToSpeech = textToSpeech;
        }

项目文件: http://www.mediafire.com/file/nl6dx5c4mc3mg63/FirstPrismApp.rar

推荐答案

Prism 7更改了此行为，因为它实际上是依赖于辅助容器的反模式.您只需要在IPlatformInitializer中注册您的TextToSpeech服务，例如:

Prism 7 changed this behavior as it is actually an anti-pattern to rely on a secondary container. You simply need to register your TextToSpeech service in the IPlatformInitializer like:

public class iOSInitializer : IPlatformInitializer
{
    public void RegisterTypes(IContainerRegistry containerRegistry)
    {
        containerRegistry.Register<ITextToSpeech, TextToSpeech_iOS>();
    }
}

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