Xamarin.Forms Prism-使用导航服务从一个详细信息页面导航到另一个

Question

In my Xamarin.Forms Prism app, I am using a MasterDetailPage for navigation.

While I am on one detail page, I would like to navigate to another detail page, as if I had selected it from the master page.

Initial navigation in App.xaml.cs:

protected override void OnInitialized()
{
   ...
   NavigationService.NavigateAsync("MainPage/RootNavigation/MyFirstPage");
}

When I click a shortcut button on MyFirstPage, I would like to go to MainPage/RootNavigation/MySecondPage. The closest that I have been able to achieve has been using an absolute Uri.

private async void OnShortcutTapped(MyModel sender)
{
  ...
  await _navigationService.NavigateAsync(new Uri("http://myapp.com/MainPage/RootNavigation/MySecondPage", UriKind.Absolute), navigationParams, null, false);
}

This basically gets me what I want, but after navigating in this manner, if I make the Master visible and select the menu item for MySecondPage, it refreshes the detail page as if it is navigating to the page.

Is there a better way to maintain this navigation, so that the master page knows that MySecondPage is already being displayed and it doesn't try to reload it?

Answer 1

While your navigation pattern doesn't make a lot of sense to me, you can achieve what you want by invoking a navigate command in the MasterDetailPageViewModel. You have a number of ways to do this. You could use the IEventAggregator to send a message to the MasterDetailPageViewModel to navigate, or you can use a CompositeCommand that invokes a DelegateCommand that exists on the MasterDetailPageViewModel.

You can see a sample of using a CompositeCommand here: https://github.com/PrismLibrary/Prism-Samples-Forms/tree/master/UsingCompositeCommands

You can also see how to send messages in this sample that I gave at the Xamarin Evolve conference: https://github.com/brianlagunas/Evolve2016SamplesAndSlides

Another option would be to just call a navigate command off the App.Current.MainPage ViewModel from with your MyFirstPage code behind.