I have a route that is registered using the following
Routing.RegisterRoute("SchoolHome", typeof(SchoolHomePage));
I have a page with a list of schools and when I tap a School it executes this just fine from the ViewModel Command
Shell.Current.GoToAsync($"SchoolHome?schoolid={selectedSchool.Id}");
Here is my SchoolHomePage.xaml.cs
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class SchoolHomePage : ContentPage
{
public SchoolHomePage()
{
InitializeComponent();
BindingContext = new SchoolHomeViewModel();
}
}
Here is a snippet of SchoolHomeViewModel.cs
[QueryProperty("School", "schoolid")]
public class SchoolHomeViewModel : BaseViewModel
{
string school;
public string School
{
get
{
return school;
}
set
{
SetProperty(ref school, Uri.UnescapeDataString(value));
}
}
So Shell doesn't map my QueryProperty to my property School and the page doesn't navigate. If I put the QueryProperty in the ContentPage's code behind and set the ViewModel's School property there, it will pass the value along but the page still doesn't navigate. It just stays on the page with the list of schools with the one I just tapped being selected.
I found the problem. I had an issue with a property in my viewmodel. Once I fixed that it worked.
Related
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 would like to ask about bindings. What is the best approach to bind some actions in listview items in ios and android using xamarin in mvvm world. As I understand, we have few approaches.
1.
For every list item we have some Model, and to this model we have to add some Commands.
For example:
public class ItemModel
{
public string MyName { get; set; }
public ICommand RemoveCommand { get; set; }
}
Where in ViewModel we have SomeInitMethod
public class ViewModel
{
public ObservableCollection<ItemModel> Items {get;set;}
public async Task SomeInitMethod
{
Items = new ObservableCollection(await _myApiService.FetchItemsAsync());
foreach(var item in Items)
{
item.Command = new RelayCommand(RemoveItem);
}
}
public void RemoveItem(ItemModel item)
{
Items.Remove(item);
}
}
But I see a drawback in SomeInitMethod where we should set RemoveCommand. What if we should to set 2 or even more commands than we duplicate code in ListItemView(somehow we need to bind all these commands)?
Next approach is somehow handle events of remove/toggle buttons and others in Listview and then delegate this commands directly to ViewModel.
Example:
ContactsListView.ItemRemoveClicked += (ItemModel model) => ViewModel.RemoveItem
Advantages is: we no longer need to handle commands in ViewModel
Drawback is: we need every time to write custom ListView and support event handling in code-behind.
The last approach is to send ViewModel to ListItem to set Commands.
Example
somewhere we have method CreateListViewItem on the view, let's say on iOS.
private void InitTableView() {
TableView.RegisterNibForCellReuse(ItemViewCell.Nib, ItemViewCell.Key);
var source = new ObservableTableViewSource <ItemModel>
{
DataSource = ViewModel.Items,
BindCellDelegate = (cell, viewModel, index) =>
{
if (cell is ItemModel memberCell)
{
memberCell.BindViewModel(viewModel);
memberCell.RemoveItem = (item) => ViewModel.RemoveItem;
}
}
};
TableView.Source = source;
}
Advantages: we no longer need to have Commands in Model, and we don't need to setup this Commands in ViewModel.
Possibly, drawback is that we somehow need to have ViewModel reference.
In WPF or UWP you have DataContext, you can binding directly to ViewModel.
Which approach you use, maybe I miss something, and it would be perfect if you provide some examples or thoughts.
Thanks.
I am trying to find a way to be able to set from the View to what ViewModel I have to navigate. This is to be able to change the navigation flow without changing the core project.
I thought the easier way would be creating an interface, setting the target ViewModel there and injecting the interface into the ViewModel to then perform the navigation.
public interface IModelMapping
{
MvxViewModel ViewModelToNavigate();
}
public class MyViewModel : MvxViewModel
{
readonly IMvxNavigationService navigationService;
readonly IModelMapping modelMapping;
public MyViewModel(IMvxNavigationService navigationService, IModelMapping modelMapping)
{
this.navigationService = navigationService;
this.modelMapping = modelMapping;
}
public IMvxAsyncCommand GoContent
{
get
{
IMvxViewModel vm = modelMapping.ViewModelToNavigate();
IMvxAsyncCommand navigateCommand = new MvxAsyncCommand(() => navigationService.Navigate<vm>());
return navigteCommand;
}
}
}
The problem with this code is I am getting an error setting the navigationService.Navigate(). The error is 'vm is a variable but it is used like a type'
What about using the URI navigation together with the facade? See also https://www.mvvmcross.com/documentation/fundamentals/navigation#uri-navigation
Say you are building a task app and depending on the type of task you want to show a different view. This is where NavigationFacades come in handy (there is only so much regular expressions can do for you).
mvx://task/?id=00 <– this task is done, show read-only view (ViewModelA)
mvx://task/?id=01 <– this task isn’t, go straight to edit view (ViewModelB)
[assembly: MvxRouting(typeof(SimpleNavigationFacade), #"mvx://task/\?id=(?<id>[A-Z0-9]{32})$")]
namespace *.NavigationFacades
{
public class SimpleNavigationFacade
: IMvxNavigationFacade
{
public Task<MvxViewModelRequest> BuildViewModelRequest(string url,
IDictionary<string, string> currentParameters, MvxRequestedBy requestedBy)
{
// you can load data from a database etc.
// try not to do a lot of work here, as the user is waiting for the UI to do something ;)
var viewModelType = currentParameters["id"] == Guid.Empty.ToString("N") ? typeof(ViewModelA) : typeof(ViewModelB);
return Task.FromResult(new MvxViewModelRequest(viewModelType, new MvxBundle(), null, requestedBy));
}
}
}
In my android project, the webview url is dynamic. I am using mvvmcros binding on view side but its not being dynamic. If the url content on view model is changing its not being updated on view. Can anyone help me out?
View
public string WebContentUrll { get; set; }
protected override void OnCreate(Android.OS.Bundle bundle)
{
var bindingSet = this.CreateBindingSet<view, ViewModel>();
bindingSet.Bind(this).For(v => v.WebContentUrll).To(vm => vm.WebContentUrl).TwoWay();
}
ViewModel
private string webContentUrl;
public string WebContentUrl
{
get
{
return webContentUrl;
}
set
{
webContentUrl = value;
RaisePropertyChanged(() => webContentUrl);
}
}
public void Init()
{
webContentUrl = "https://.."'
}
The value of web content url in the view model changes after the page is loaded but the android view is not able to get the new updated url.
Can anyone please advise. Thank you.
Update
The web view is opened on a button click and the url is updated after the page loads and before the button is clicked
From you description in the opening post. In your Activity you have defined a property WebContentUrll. You want to bind this and update something when it is changed.
The definition of WebContentUrll is:
public string WebContentUrll { get; set; }
This is not wrong and you should see the value reflected in WebContentUrll when it changes from the ViewModel through your binding. However, there is no code updating any visual states, views or anything based on that property.
If you have a WebView you want to change content for, you could modify your property to something like:
private string _webContentUrll;
public string WebContentUrll
{
get => _webContentUrll;
set
{
_webContentUrll = value;
_webView.LoadUrl(_webContentUrll);
}
}
Given that _webView is your instance of a WebView.
I'm new to Xamarin and C#, so apologies in advance for any mistakes I make.
In my app, I have a list of plants. When a plant is selected, I have a detail view of info about the plant. In the detail view, I have a button that adds or removes the plant from a shopping list.
To implement this, I have a class named MyPlant, with a field called InCart, and a method ToggleInCart that the button calls.
(note that I didn't paste in some code to simplify this question as much as possible)
public class MyPlant : INotifyPropertyChanged
{
string name;
bool inCart;
...
public bool InCart
{
set
{
if (inCart != value)
{
inCart = value;
OnPropertyChanged("InCart");
}
}
get { return inCart; }
}
public ICommand ToggleCartStatus
{
get
{
if (_toggleCartStatus == null)
{
_toggleCartStatus = new Command(() => InCart = !InCart);
}
return _toggleCartStatus;
}
I have another class called PlantList, which has a method PlantsInCart that uses LINQ to return an ObservableCollection of MyPlant where InCart is true.
public class PlantList : INotifyPropertyChanged
{
public ObservableCollection PlantsInCart
{
private set { }
get
{
ObservableCollection list = new ObservableCollection(myPlants.Where(i => i.InCart));
return list;
}
}
In my XAML, I have a ListView bound to PlantsInCart.
Everything works as I want EXCEPT when I remove the selected plant, the list doesn't update to show the plant is missing even though the data underneath it is correctly updated. If I refresh the list by going to a different page and coming back, then the list shows the right plants.
I suspect this doesn't work because the change in the InCart field isn't bubbling up high enough to that the ListView hears that it is supposed to update.
Can anybody advise me on the proper way to implement this kind of feature? In other words, how should you implement a scenario where you have a list that should update when a property of an item in the list changes?