我正在尝试为 UWP 上的 Xamarin Map 编写自定义渲染器，并且 PCL 中的集合更改事件未触发 UWP 自定义渲染器中的相应事件。它在 iOS 和 Android 上运行良好。
使用以下代码，即使每 5 秒调用一次 OnItemsSourcePropertyChanged，也不会在 CustomMapRenderer 中调用事件 ItemsCollectionChanged。
public class CustomMap : Map
{
#region << Events >>
public event EventHandler ItemsCollectionChanged;
#endregion
private static void OnItemsSourcePropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
var map = bindable as CustomMap;
if (map == null)
return;
map.ItemsSource.CollectionChanged += (s, e) =>
{
SetPin(bindable);
if (map.ItemsCollectionChanged != null)
{
map.ItemsCollectionChanged(bindable, new EventArgs());
}
};
}
}
[assembly: ExportRenderer(typeof(CustomMap), typeof(CustomMapRenderer))]
Namespace MyNamespace.Renderers
{
public class CustomMapRenderer : MapRenderer
{
MapControl _nativeMap;
protected override void OnElementChanged(ElementChangedEventArgs<Map> e)
{
base.OnElementChanged(e);
if (e.OldElement != null)
{
_nativeMap.MapElementClick -= OnMapElementClick;
_nativeMap.Children.Clear();
_nativeMap = null;
}
if (e.NewElement != null)
{
var formsMap = (CustomMap)e.NewElement;
formsMap.ItemsCollectionChanged += ItemsCollectionChanged;
_pinClickedCommand = formsMap.PinClickedCommand;
_routeCoordinates = formsMap.ItemsSource;
_nativeMap = Control as MapControl;
_nativeMap.Children.Clear();
_nativeMap.MapElementClick += OnMapElementClick;
var snPosition = new BasicGeoposition { Latitude = 45, Longitude = -88 };
Geopoint snPoint = new Geopoint(snPosition);
var mapIcon = new MapIcon();
if (mapIcon != null)
{
_nativeMap.MapElements.Remove(mapIcon);
}
mapIcon.CollisionBehaviorDesired = MapElementCollisionBehavior.RemainVisible;
mapIcon.Location = snPoint;
mapIcon.NormalizedAnchorPoint = new Windows.Foundation.Point(0.5, 1.0);
_nativeMap.MapElements.Add(mapIcon);
_nativeMap.Center = snPoint;
}
}
void ItemsCollectionChanged(object sender, EventArgs e)
{
;
}
}
}