| id | title | brief | samplecode | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
SearchController |
UISearchController is used to display and manage searching in your application |
|
UISearchController has replaced UISearchDisplayController as a way to manage the presentation of a search bar and search results starting with iOS 8. UISearchDisplayController is now deprecated.
UISearchController is a View Controller that manages all aspects of searching in your application: the search bar, displaying the search results, and updating search results as the user interacts with the search bar:
All three of these elements can be configured through properties on the UISearchController:
SearchBar- This is created automatically and exposed through a readonly property.
- You are responsible for placing the SearchBar. For example, if your first View Controller is a TableViewController, you could place it in the header by using the following code:
TableView.TableHeaderView = SearchController.SearchBar;SearchResultsController- This is the 2nd View Controller in the image above, and displays the results of your search.
- Any type of View Controller can be used, but usually a TableViewController works best
- This is passed to the constructor of the search controller.
SearchResultsUpdater- You implement this object, but it must adopt the
UISearchResultsUpdatingprotocol. - It receives notifications about the searches and is responsible for updating the UI
- It is responsible for updating the results with each keystroke
- It acts as a mediator between the search controller's search bar and search results.
- You implement this object, but it must adopt the
This is example is taken from the MapDemo sample, and relates to implementing a local search on a map, and then displaying a pin and annonation on the selected result. You can find the full sample in the MapsDemo folder here.
The following code adds a UISearchController (which has a search bar property) in the ViewDidLoad method of MapViewController:
//Creates an instance of a custom View Controller that holds the results
var searchResultsController = new SearchResultsViewController (map);
//Creates a search controller updater
var searchUpdater = new SearchResultsUpdator ();
searchUpdater.UpdateSearchResults += searchResultsController.Search;
//add the search controller
searchController = new UISearchController (searchResultsController) {
SearchResultsUpdater = searchUpdater
};
//format the search bar
searchController.SearchBar.SizeToFit ();
searchController.SearchBar.SearchBarStyle = UISearchBarStyle.Minimal;
searchController.SearchBar.Placeholder = "Enter a search query";
//the search bar is contained in the navigation bar, so it should be visible
searchController.HidesNavigationBarDuringPresentation = false;
//Ensure the searchResultsController is presented in the current View Controller
DefinesPresentationContext = true;
//Set the search bar in the navigation bar
NavigationItem.TitleView = searchController.SearchBar;
##Displaying the Search Results
The following code is an example of how to create the search result custom View Controller:
public class SearchResultsViewController : UITableViewController
{
static readonly string mapItemCellId = "mapItemCellId";
MKMapView map;
public List<MKMapItem> MapItems { get; set; }
public SearchResultsViewController (MKMapView map)
{
this.map = map;
MapItems = new List<MKMapItem> ();
}
public override nint RowsInSection (UITableView tableView, nint section)
{
return MapItems.Count;
}
public override UITableViewCell GetCell (UITableView tableView, NSIndexPath indexPath)
{
var cell = tableView.DequeueReusableCell (mapItemCellId);
if (cell == null)
cell = new UITableViewCell ();
cell.TextLabel.Text = MapItems [indexPath.Row].Name;
return cell;
}
public override void RowSelected (UITableView tableView, NSIndexPath indexPath)
{
// add item to map
CLLocationCoordinate2D coord = MapItems [indexPath.Row].Placemark.Location.Coordinate;
map.AddAnnotations (new MKPointAnnotation () {
Title = MapItems [indexPath.Row].Name,
Coordinate = coord
});
map.SetCenterCoordinate (coord, true);
DismissViewController (false, null);
}
public void Search (string forSearchString)
{
// create search request
var searchRequest = new MKLocalSearchRequest ();
searchRequest.NaturalLanguageQuery = forSearchString;
searchRequest.Region = new MKCoordinateRegion (map.UserLocation.Coordinate, new MKCoordinateSpan (0.25, 0.25));
// perform search
var localSearch = new MKLocalSearch (searchRequest);
localSearch.Start (delegate (MKLocalSearchResponse response, NSError error) {
if (response != null && error == null) {
this.MapItems = response.MapItems.ToList ();
this.TableView.ReloadData ();
} else {
Console.WriteLine ("local search error: {0}", error);
}
});
}
}
The following code shows the first step of creating the search method in the SearchResultsViewController:
public void Search (string forSearchString)
{
// create search request
var searchRequest = new MKLocalSearchRequest ();
searchRequest.NaturalLanguageQuery = forSearchString;
searchRequest.Region = new MKCoordinateRegion (map.UserLocation.Coordinate, new MKCoordinateSpan (0.25, 0.25));
// perform search
var localSearch = new MKLocalSearch (searchRequest);
localSearch.Start (delegate (MKLocalSearchResponse response, NSError error) {
if (response != null && error == null) {
this.MapItems = response.MapItems.ToList ();
this.TableView.ReloadData ();
} else {
Console.WriteLine ("local search error: {0}", error);
}
});
}
Then creating a custom implementation of UISearchResultsUpdating:
public class SearchResultsUpdator : UISearchResultsUpdating
{
public event Action<string> UpdateSearchResults = delegate {};
public override void UpdateSearchResultsForSearchController (UISearchController searchController)
{
this.UpdateSearchResults (searchController.SearchBar.Text);
}
}
