Implementing a UISearchController using MVVMCross - xamarin

Question

I have an app which I am converting from iOS only to iOS & Droid using MVVMCross.
In my current app I have a map view that uses a UISearchController that allows the user to search for locations nearby. This is based on the Xamarin example and works fine:
Xamarin Map Example
For the conversion I have:
a MapView bound to a MapViewModel.
A search service which is injected into MapViewModel.
Created a UISearchController and bound the search text to a property on the MapViewModel.
When the text is updated the search is called and the results are retrieved. What I am struggling with is how to bind the results back to a SearchResultsView as this is presented by the UISearchController.
Can anyone give me advice or point me in the right direction to solve this.
I have the code snippet below to give an idea of what I have relied so far.
[MvxFromStoryboard]
public partial class MapView : MvxViewController<MapViewModel>
{
public MapView(IntPtr handle) : base(handle)
{
}
public override void ViewDidLoad()
{
base.ViewDidLoad();
var searchResultsController = new SearchResultsView();
//Not sure if this is required
//var searchUpdater.UpdateSearchResults += searchResultsController.Search;
var searchController = new UISearchController(searchResultsController)
{
//Nore sure if this is required
//SearchResultsUpdater = searchUpdater
};
searchController.SearchBar.SizeToFit();
searchController.SearchBar.SearchBarStyle = UISearchBarStyle.Minimal;
searchController.SearchBar.Placeholder = "Enter a search query";
searchController.HidesNavigationBarDuringPresentation = false;
DefinesPresentationContext = true;
NavigationItem.TitleView = searchController.SearchBar;
//Bind to View Model
var set = this.CreateBindingSet<MapView, MapViewModel>();
set.Bind(searchController.SearchBar).To(vm => vm.SearchQuery);
set.Apply();
}
}
public class SearchResultsUpdator : UISearchResultsUpdating
{
public event Action<string> UpdateSearchResults = delegate { };
public override void UpdateSearchResultsForSearchController(UISearchController searchController)
{
this.UpdateSearchResults(searchController.SearchBar.Text);
}
}
[MvxFromStoryboard]
public partial class SearchResultsView : MvxTableViewController<SearchResultsViewModel>
{
public SearchResultsView() { }
public SearchResultsView(IntPtr handle) : base(handle)
{
}
public override void ViewDidLoad()
{
base.ViewDidLoad();
var source = new SearchResultsTableViewSource(TableView);
TableView.Source = source;
var set = this.CreateBindingSet<SearchResultsView, SearchResultsViewModel>();
set.Bind(source).To(vm => vm.Results);
set.Apply();
}
}
[MvxFromStoryboard]
public partial class SearchResultsView : MvxTableViewController<SearchResultsViewModel>
{
public SearchResultsView() { }
public SearchResultsView(IntPtr handle) : base(handle)
{
}
public override void ViewDidLoad()
{
base.ViewDidLoad();
var source = new SearchResultsTableViewSource(TableView);
TableView.Source = source;
var set = this.CreateBindingSet<SearchResultsView, SearchResultsViewModel>();
set.Bind(source).To(vm => vm.Results);
set.Apply();
}
}

Answer 1

I have posted this in case someone else is looking for an example. I decided the best way to do this was to let iOS handle the search view controller for the results. Code follows. Feel free to correct or suggest a better alternative
View
[MvxFromStoryboard]
public partial class MapView : MvxViewController
{
UISearchController _searchController;
SearchResultsViewController _searchResultsController;
private IDisposable _searchResultsUpdateSubscription;
private IMvxInteraction _searchResultsUpdatedInteraction;
public IMvxInteraction SearchResultsUpdatedInteraction
{
get => _searchResultsUpdatedInteraction;
set
{
if (_searchResultsUpdateSubscription != null)
{
_searchResultsUpdateSubscription.Dispose();
_searchResultsUpdateSubscription = null;
}
_searchResultsUpdatedInteraction = value;
if (_searchResultsUpdatedInteraction != null)
{
_searchResultsUpdateSubscription = _searchResultsUpdatedInteraction.WeakSubscribe(OnSearchResultsUpdated);
}
}
}
private void OnSearchResultsUpdated(object sender, EventArgs e)
{
_searchResultsController.SearchResults = Results;
_searchResultsController.ReloadSearchTable();
}
public List<Placemark> Results { get; set; }
public MapView(IntPtr handle) : base(handle)
{
}
public override void ViewDidLoad()
{
base.ViewDidLoad();
//Bind to View Model
var set = this.CreateBindingSet<MapView, MapViewModel>();
set.Bind(_searchController.SearchBar).To(vm => vm.SearchQuery);
set.Bind(this).For(v => v.Results).To(vm => vm.Results);
set.Bind(this).For(v => v.SearchResultsUpdatedInteraction).To(vm => vm.SearchResultsUpdatedInteraction).OneWay();
set.Apply();
}
ViewModel
public class MapViewModel : MvxViewModel
{
readonly ILocationService _locationService;
private MvxInteraction _searchResultsUpdatedInteraction = new MvxInteraction();
public IMvxInteraction SearchResultsUpdatedInteraction => _searchResultsUpdatedInteraction;
public MapViewModel(ILocationService locationService)
{
_locationService = locationService;
}
//***** Properties *****
private List<Placemark> _results;
public List<Placemark> Results
{
get => _results;
set
{
_results = value;
RaisePropertyChanged();
}
}
private string _searchQuery;
public string SearchQuery
{
get => _searchQuery;
set
{
_searchQuery = value;
//Task.Run(UpdateResultsAsync).Wait();
RaisePropertyChanged();
UpdateResultsAsync();
}
}
//***** Privates *****
private async Task UpdateResultsAsync()
{
Results = await _locationService.SearchForPlacesAsync(_searchQuery);
_searchResultsUpdatedInteraction.Raise();
}
}
SearchResultsViewController
public class SearchResultsViewController : UITableViewController
{
static readonly string mapItemCellId = "mapItemCellId";
public List<Placemark> SearchResults { get; set; }
public SearchResultsViewController()
{
SearchResults = new List<Placemark>();
}
public override nint RowsInSection(UITableView tableView, nint section)
{
return SearchResults == null ? 0 : SearchResults.Count;
}
public override UITableViewCell GetCell(UITableView tableView, NSIndexPath indexPath)
{
var cell = tableView.DequeueReusableCell(mapItemCellId);
if (cell == null)
cell = new UITableViewCell();
cell.TextLabel.Text = SearchResults[indexPath.Row].FeatureName;
return cell;
}
public override void RowSelected(UITableView tableView, NSIndexPath indexPath)
{
//Do stuff here
}
public void ReloadSearchTable()
{
this.TableView.ReloadData();
}
}