Any Solution to know if content page is active or called inside a AppDelegate.cs ?
because iv installed a plugin NFC, and i want to active the plugin only when NFC.xaml page is active, not when starting the application.
in this code am trying to begin session only When page NFC.xaml is active or called
public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
{
public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
// if(App.Current==NFC.xaml) any way to know the content page ?
Session = new NFCNdefReaderSession(this, null, true);
Session?.BeginSession();```
}
}
When a page is getting active OnAppearing method would be triggered .
So we could use MessagingCenter here .
NFC.xaml.cs
protected override void OnAppearing()
{
base.OnAppearing();
MessagingCenter.Send<object>(this,"Hi");
}
AppDelegate.cs
public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
{
public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
MessagingCenter.Subscribe<object>(this, "Hi", (obj) =>
{
Session = new NFCNdefReaderSession(this, null, true);
Session?.BeginSession();
});
}
}
Related
I have Label in view, I need that Label's view in my ViewModel. I am using Dependency Service to set focus on Controls for Accessibility service, DS requires view as a param.
This is my Label
<Label
AutomationProperties.IsInAccessibleTree="{Binding ShowNoResults}"
IsVisible="{Binding ShowNoResults}"
Text="{Binding ResultsHeader}"/>
I tried Command but Label doesn't support command. Below code also not working
var view = GetView() as HomeworkView;
I am getting view always null. How can I fix this?
I am not quite sure what are you trying to achieve, but you can't access the View elements from you view model.
If you want to do something with the control, you can use the messaging center to do it, here is an example
in your ViewModel
MessagingCenter.Send(this, "your message here");
then in your page, you need to subscribe to this message from that view model and do the desired action
MessagingCenter.Instance.Unsubscribe<ViewModelClassNamedel>(this, "your message here");
MessagingCenter.Instance.Subscribe<ViewModelClassName>(this, "your message here", (data) =>
{
this.youControlName.Focus();
});
More detail added to Mohammad's answer.
Message Center doc.
In your ViewModel (with class name "YourViewModel"):
// Here we use control name directly.
// OR could make an "enum" with a value for each control.
string controlName = ...;
MessagingCenter.Send<YourViewModel>(this, "focus", controlName);
then in your page, subscribe to this message and do the desired action
.xaml.cs:
protected override void OnAppearing() {
{
base.OnAppearing();
// Unsubscribe before Subscribe ensures you don't Subscribe twice, if the page is shown again.
MessagingCenter.Instance.Unsubscribe<YourViewModel>(this, "focus");
MessagingCenter.Instance.Subscribe<YourViewModel>(this, "focus", (controlName) =>
{
View v = null;
switch (controlName) {
case "name1":
v = this.name1;
break;
case "name2":
v = this.name2;
break;
}
if (v != null) {
//v.Focus();
// Tell VM to use v as view.
((YourViewModel)BindingContext).SetFocus(v);
}
});
}
protected override void OnDisappearing() {
MessagingCenter.Instance.Unsubscribe<YourViewModel>(this, "focus");
base.OnDisappearing();
}
If need to pass View v back to VM, because that has the logic to use it:
public class YourViewModel
{
public void SetFocus(View view)
{
... your code that needs label's view ...
}
}
Not tested. Might need some slight changes. Might need
...(this, "focus", (sender, controlName) =>
instead of
...(this, "focus", (controlName) =>
UPDATE
Simple approach, if there is only ONE View that is needed in VM.
public class YourViewModel
{
public View ViewToFocus { get; set; }
// The method that needs ViewToFocus.
void SomeMethod()
{
...
if (ViewToFocus != null)
... do something with it ...
}
}
public class YourView
{
public YourView()
{
InitializeComponent();
...
// After BindingContext is set.
((YourViewModel)BindingContext).ViewToFocus = this.yourLabelThatShouldBeFocused;
}
}
ALTERNATIVE: It might be cleaner/more robust to set ViewToFocus in page's OnAppearing, and clear it in OnDisappearing. This ensures it is never used while the page is not visible (or in some delayed action after the page has gone away). I would probably do it this way.
protected override void OnAppearing()
{
base.OnAppearing();
((YourViewModel)BindingContext).ViewToFocus = this.yourLabelThatShouldBeFocused;
}
protected override void OnDisappearing()
{
((YourViewModel)BindingContext).ViewToFocus = null;
base.OnDisappearing();
}
I want to open a pop up window using xamarin comunity toolkit extensions but when i try to call
Navigation it says that it does not exist even if i have included xct.extensions. There is NavigationExtensions but I don't know what I'm supposed to pass as first parameter and it says that my FilterPopup is of incorect type
using Xamarin.CommunityToolkit.Extensions;
namespace Appointments.ViewModels
{
public class WallViewModel
{
public ObservableCollection<Stylist> Stylists { get; set; }
public AsyncCommand OpenModalFiltersComand;
public WallViewModel()
{
OpenModalFiltersComand = new AsyncCommand(OpenModalFilters);
}
async Task OpenModalFilters()
{
NavigationExtensions.ShowPopup(AppShell, FilterPopup);
Navigation // error
}
}
}
My FilterPopup
namespace Appointments.Popups
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class FilterPopup : Popup
{
public FilterPopup()
{
InitializeComponent();
}
}
}
EDIT---------
I'm using shell navigation
ShowPopup takes an INavigation and an instance of a PopupBase. Navigation is a property of Page types, so your VM does not have a reference to it.
var nav = App.Current.MainPage.Navigation;
var filter = new FilterPopup();
NavigationExtensions.ShowPopup(nav, filter);
I'm looking to improve my mobile application developed in Xamarin.Forms.
My functionality is as follows: onResume of the application I want to reload the page on which the user was.
Currently I use the MessagingCenter to operate with the code below.
Unfortunately my application is starting to have a lot of pages and it's not very readable anymore.
I am therefore looking to pass my type (viewModel) as a parameter of my navigation service - my research directs me towards the concept of reflection but I don't know if my problem is achievable.
// App.xaml.cs
protected override void OnResume()
{
// Handle when your app resumes
Page currPage = ((NavigationPage)((MasterDetailPage)Application.Current.MainPage).Detail).CurrentPage;
MessagingCenter.Send<App, Page>(this, "Hi", currPage);
}
Then in my BaseViewModel :
// BaseViewModel.cs
public ViewModelBase()
{
DialogService = ViewModelLocator.Instance.Resolve<IDialogService>();
NavigationService = ViewModelLocator.Instance.Resolve<INavigationService>();
AuthenticationService = ViewModelLocator.Instance.Resolve<IAuthenticationService>();
MessagingCenter.Subscribe<App, Page>(this, "Hi", async (sender, arg) =>
{
// Do something whenever the "Hi" message is received
Type viewModel = NavigationService.GetViewModelTypeForPage(arg.GetType());
if(viewModel == typeof(AboutViewModel))
{
Debug.WriteLine("AboutViewModel");
await NavigationService.NavigateToAsync<AboutViewModel>();
return;
}
if (viewModel == typeof(CardViewModel))
{
Debug.WriteLine("CardViewModel");
await NavigationService.NavigateToAsync<CardViewModel>();
return;
}
...
});
}
I would give you some ideas on how to make your code readable when using MessagingCenter.
First, you can have a BasePage which implemented the MessagingCenter.Subscribe and a method which called loadData:
public partial class BasePage : ContentPage
{
public BasePage()
{
MessagingCenter.Subscribe<App, string>(this, "Hi", (sender, arg) =>
{
// Do something whenever the "Hi" message is received
loadData();
});
}
public virtual void loadData()
{
}
}
Then, when you create a new page which need to refresh when the application is resumed, you can make the page inherits from the BasePage type:
public partial class MainPage : BasePage
{
public MainPage()
{
InitializeComponent();
loadData();
}
public override void loadData()
{
base.loadData();
Console.WriteLine("loadData");
}
}
And the xaml:
<?xml version="1.0" encoding="utf-8" ?>
<bases:BasePage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:bases="clr-namespace:App52"
mc:Ignorable="d"
x:Class="App52.MainPage">
</bases:BasePage>
So you don't have to implement MessagingCenter.Subscribe in each Page, those can be managed in BasePage.
I'm not familiar with reflection so maybe can't help you on achieving that by reflection. Hope this helps.
I am facing a very weird issue, I am showing categories to user using horizontal CollectionView in Xamarin.iOS and i am using MvvMCross as well. The issue is that that when i scroll the categories CollectionView and scroll back some of the cells are empty.
This is the code for the subclass of the MvxCollectionViewCell in which i am binding values to the UI.
public partial class DealListCategoryCollectionCellView : MvxCollectionViewCell
{
public static readonly UINib Nib = UINib.FromName("DealListCategoryCollectionCellView", NSBundle.MainBundle);
public static readonly NSString Key = new NSString("CategoryCollectionViewCell");
private FXMvxImageViewLoader _imageLoader;
public DealListCategoryCollectionCellView(IntPtr handle) : base(handle)
{
_imageLoader = new FXMvxImageViewLoader(() => CategoryImageView);
this.DelayBind(() =>
{
var set = this.CreateBindingSet<DealListCategoryCollectionCellView, CategoryCellViewModel>();
set.Bind(TitleLabel).To(vm => vm.Name);
set.Bind(_imageLoader).To(vm => vm.Slug).WithConversion("LocalImage", "icons");
set.Apply();
});
}
public static DealListCategoryCollectionCellView Create()
{
return (DealListCategoryCollectionCellView)Nib.Instantiate(null, null)[0];
}
}
And this is how i am binding the above collectionview Cell.
CategoryCollectionView.RegisterNibForCell(DealListCategoryCollectionCellView.Nib, DealListCategoryCollectionCellView.Key);
var categorySource = new MvxCollectionViewSource(CategoryCollectionView,DealListCategoryCollectionCellView.Key);
CategoryCollectionView.Source = categorySource;
And this is the screenshot of the issue :
I have fixed the issue by first changing this:
CategoryCollectionView.Source = categorySource;
to:
CategoryCollectionView.DataSource = categorySource;
So when i changed from Source to DataSource the empty cell issue was fixed but there was another issue my tap on cell was not being fired. So i implemented CollectionViewDelegate like this:
class CategoryCollectionDelegate : UICollectionViewDelegate
{
DealListViewModel viewModel;
public CategoryCollectionDelegate(DealListViewModel vm)
{
viewModel = vm;
}
public override void ItemSelected(UICollectionView collectionView, NSIndexPath indexPath)
{
Category currentCategory = viewModel.Categories[indexPath.Row];
Console.WriteLine(currentCategory.Name);
viewModel.DoSelectCategoryCommand(currentCategory);
}
}
And than i used it like that :
CategoryCollectionView.Delegate = new CategoryCollectionDelegate(DealListViewModel);
And it worked like charm :)
the solution for me was to overwrite the CellDisplayingEnded method in the CollectionViewSource. As you see here https://github.com/MvvmCross/MvvmCross/blob/develop/MvvmCross/Binding/iOS/Views/MvxBaseCollectionViewSource.cs there is some commented code in CellDisplayingEnded method which maybe in some version of mvvmcross is not commented and dataContext is set to null.
I have the following code in my Android app, it basically uses one page (using a NavigationDrawer) and swaps fragments in/out of the central view. This allows the navigation to occur on one page instead of many pages:
Setup.cs:
protected override IMvxAndroidViewPresenter CreateViewPresenter()
{
var customPresenter = new MvxFragmentsPresenter();
Mvx.RegisterSingleton<IMvxFragmentsPresenter>(customPresenter);
return customPresenter;
}
ShellPage.cs
public class ShellPage : MvxCachingFragmentCompatActivity<ShellPageViewModel>, IMvxFragmentHost
{
.
.
.
public bool Show(MvxViewModelRequest request, Bundle bundle)
{
if (request.ViewModelType == typeof(MenuContentViewModel))
{
ShowFragment(request.ViewModelType.Name, Resource.Id.navigation_frame, bundle);
return true;
}
else
{
ShowFragment(request.ViewModelType.Name, Resource.Id.content_frame, bundle, true);
return true;
}
}
public bool Close(IMvxViewModel viewModel)
{
CloseFragment(viewModel.GetType().Name, Resource.Id.content_frame);
return true;
}
.
.
.
}
How can I achieve the same behavior in a Windows UWP app? Or rather, is there ANY example that exists for a Windows MvvmCross app which implements a CustomPresenter? That may at least give me a start as to how to implement it.
Thanks!
UPDATE:
I'm finally starting to figure out how to go about this with a customer presenter:
public class CustomPresenter : IMvxWindowsViewPresenter
{
IMvxWindowsFrame _rootFrame;
public CustomPresenter(IMvxWindowsFrame rootFrame)
{
_rootFrame = rootFrame;
}
public void AddPresentationHintHandler<THint>(Func<THint, bool> action) where THint : MvxPresentationHint
{
throw new NotImplementedException();
}
public void ChangePresentation(MvxPresentationHint hint)
{
throw new NotImplementedException();
}
public void Show(MvxViewModelRequest request)
{
if (request.ViewModelType == typeof(ShellPageViewModel))
{
//_rootFrame?.Navigate(typeof(ShellPage), null); // throws an exception
((Frame)_rootFrame.UnderlyingControl).Content = new ShellPage();
}
}
}
When I try to do a navigation to the ShellPage, it fails. So when I set the Content to the ShellPage it works, but the ShellPage's ViewModel is not initialized automatically when I do it that way. I'm guessing ViewModels are initialized in MvvmCross using OnNavigatedTo ???
I ran into the same issue, and built a custom presenter for UWP. It loans a couple of ideas from an Android sample I found somewhere, which uses fragments. The idea is as follows.
I have a container view which can contain multiple sub-views with their own ViewModels. So I want to be able to present multiple views within the container.
Note: I'm using MvvmCross 4.0.0-beta3
Presenter
using System;
using Cirrious.CrossCore;
using Cirrious.CrossCore.Exceptions;
using Cirrious.MvvmCross.ViewModels;
using Cirrious.MvvmCross.Views;
using Cirrious.MvvmCross.WindowsUWP.Views;
using xxxxx.WinUniversal.Extensions;
namespace xxxxx.WinUniversal.Presenters
{
public class MvxWindowsMultiRegionViewPresenter
: MvxWindowsViewPresenter
{
private readonly IMvxWindowsFrame _rootFrame;
public MvxWindowsMultiRegionViewPresenter(IMvxWindowsFrame rootFrame)
: base(rootFrame)
{
_rootFrame = rootFrame;
}
public override async void Show(MvxViewModelRequest request)
{
var host = _rootFrame.Content as IMvxMultiRegionHost;
var view = CreateView(request);
if (host != null && view.HasRegionAttribute())
{
host.Show(view as MvxWindowsPage);
}
else
{
base.Show(request);
}
}
private static IMvxWindowsView CreateView(MvxViewModelRequest request)
{
var viewFinder = Mvx.Resolve<IMvxViewsContainer>();
var viewType = viewFinder.GetViewType(request.ViewModelType);
if (viewType == null)
throw new MvxException("View Type not found for " + request.ViewModelType);
// Create instance of view
var viewObject = Activator.CreateInstance(viewType);
if (viewObject == null)
throw new MvxException("View not loaded for " + viewType);
var view = viewObject as IMvxWindowsView;
if (view == null)
throw new MvxException("Loaded View is not a IMvxWindowsView " + viewType);
view.ViewModel = LoadViewModel(request);
return view;
}
private static IMvxViewModel LoadViewModel(MvxViewModelRequest request)
{
// Load the viewModel
var viewModelLoader = Mvx.Resolve<IMvxViewModelLoader>();
return viewModelLoader.LoadViewModel(request, null);
}
}
}
IMvxMultiRegionHost
using Cirrious.MvvmCross.ViewModels;
using Cirrious.MvvmCross.WindowsUWP.Views;
namespace xxxxx.WinUniversal.Presenters
{
public interface IMvxMultiRegionHost
{
void Show(MvxWindowsPage view);
void CloseViewModel(IMvxViewModel viewModel);
void CloseAll();
}
}
RegionAttribute
using System;
namespace xxxxx.WinUniversal.Presenters
{
[AttributeUsage(AttributeTargets.Class)]
public sealed class RegionAttribute
: Attribute
{
public RegionAttribute(string regionName)
{
Name = regionName;
}
public string Name { get; private set; }
}
}
These are the three foundational classes you need. Next you'll need to implement the IMvxMultiRegionHost in a MvxWindowsPage derived class.
This is the one I'm using:
HomeView.xaml.cs
using System;
using System.Diagnostics;
using System.Linq;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;
using Cirrious.MvvmCross.ViewModels;
using Cirrious.MvvmCross.WindowsUWP.Views;
using xxxxx.Shared.Controls;
using xxxxx.WinUniversal.Extensions;
using xxxxx.WinUniversal.Presenters;
using xxxxx.Core.ViewModels;
namespace xxxxx.WinUniversal.Views
{
public partial class HomeView
: MvxWindowsPage
, IMvxMultiRegionHost
{
public HomeView()
{
InitializeComponent();
}
// ...
public void Show(MvxWindowsPage view)
{
if (!view.HasRegionAttribute())
throw new InvalidOperationException(
"View was expected to have a RegionAttribute, but none was specified.");
var regionName = view.GetRegionName();
RootSplitView.Content = view;
}
public void CloseViewModel(IMvxViewModel viewModel)
{
throw new NotImplementedException();
}
public void CloseAll()
{
throw new NotImplementedException();
}
}
}
The last piece to make this work is the way the actual xaml in the view is set-up. You'll notice that I'm using a SplitView control, and that I'm replacing the Content property with the new View that's coming in in the ShowView method on the HomeView class.
HomeView.xaml
<SplitView x:Name="RootSplitView"
DisplayMode="CompactInline"
IsPaneOpen="false"
CompactPaneLength="48"
OpenPaneLength="200">
<SplitView.Pane>
// Some ListView with menu items.
</SplitView.Pane>
<SplitView.Content>
// Initial content..
</SplitView.Content>
</SplitView>
EDIT:
Extension Methods
I forgot to post the two extension methods to determine if the view declares a [Region] attribute.
public static class RegionAttributeExtentionMethods
{
public static bool HasRegionAttribute(this IMvxWindowsView view)
{
var attributes = view
.GetType()
.GetCustomAttributes(typeof(RegionAttribute), true);
return attributes.Any();
}
public static string GetRegionName(this IMvxWindowsView view)
{
var attributes = view
.GetType()
.GetCustomAttributes(typeof(RegionAttribute), true);
if (!attributes.Any())
throw new InvalidOperationException("The IMvxView has no region attribute.");
return ((RegionAttribute)attributes.First()).Name;
}
}
Hope this helps.
As the link to the blog of #Stephanvs is no longer active I was able to pull the content off the Web Archive, i'll post it here for who ever is looking for it:
Implementing a Multi Region Presenter for Windows 10 UWP and MvvmCross
18 October 2015 on MvvmCross, Xamarin, UWP, Windows 10, Presenter > Universal Windows Platform
I'm upgrading a Windows Store app to the new Windows 10 Universal
Windows Platform. MvvmCross has added support for UWP in v4.0-beta2.
A new control in the UWP is the SplitView control. Basically it
functions as a container view which consist of two sub views, shown
side-by-side. Mostly it's used to implement the (in)famous hamburger
menu.
By default MvvmCross doesn't know how to deal with the SplitView, and
just replaces the entire screen contents with a new View when
navigating between ViewModels. If however we want to lay-out our views
differently and show multiple views within one window, we need a
different solution. Luckily we can plug-in a custom presenter, which
will take care of handling the lay-out per platform.
Registering the MultiRegionPresenter
In the Setup.cs file in your UWP project, you can override the
CreateViewPresenter method with the following implementation.
protected override IMvxWindowsViewPresenter CreateViewPresenter(IMvxWindowsFrame rootFrame)
{
return new MvxWindowsMultiRegionViewPresenter(rootFrame);
}
Using Regions
We can define a region by declaring a
element. At this point it has to be a Frame type because then we can
also show a nice transition animation when switching views.
<mvx:MvxWindowsPage ...>
<Grid>
<!-- ... -->
<SplitView>
<SplitView.Pane>
<!-- Menu Content as ListView or something similar -->
</SplitView.Pane>
<SplitView.Content>
<Frame x:Name="MainContent" />
</SplitView.Content>
</SplitView>
</Grid>
</mvx:MvxWindowsPage>
Now we want to be able when a ShowViewModel(...) occurs to swap out
the current view presented in the MainContent frame.
Showing Views in a Region
In the code-behind for a View we can now declare a MvxRegionAttribute,
defining in which region we want this View to be rendered. This name
has to match a Frame element in the view.
[MvxRegion("MainContent")]
public partial class PersonView
{
// ...
}
It's also possible to declare multiple regions within the same view.
This would allow you to split up your UI in more re-usable pieces.
Animating the Transition between Content Views
If you want a nice animation when transitioning between views in the
Frame, you can add the following snippet to the Frame declaration.
<Frame x:Name="MainContent">
<Frame.ContentTransitions>
<TransitionCollection>
<NavigationThemeTransition>
<NavigationThemeTransition.DefaultNavigationTransitionInfo>
<EntranceNavigationTransitionInfo />
</NavigationThemeTransition.DefaultNavigationTransitionInfo>
</NavigationThemeTransition>
</TransitionCollection>
</Frame.ContentTransitions>
</Frame>
The contents will now be nicely animated when navigating.
Hope this helps, Stephanvs