最近项目中需要用到在TOC监听图层的变化，从而针对添加的不同图层进行不同的操作。但是当TOC中添加图层组时，无法监听到图层组中添加图层的动作。也就无法获取到向图层组中添加的图层。
在开发手册中也没有找到相应的事件接口来实现。于是就动手自己写了一个事件监听。
实现的思路是，自己构建事件接口，然后构建一个GroupLayer的子类来实现这个接口。
具体看代码：
///
/// 事件接口的代码// 构建图层组图层增加的委托public delegate void IGroupLayerEvents_ItemAddedEventHandler(object Item);// 构建图层组图层移除的委托public delegate void IGroupLayerEvents_ItemDeletedEventHandler(object Item);// 构建图层组事件接口public interface IGroupLayerEvents{// 增加项事件event IGroupLayerEvents_ItemAddedEventHandler ItemAdded;// 移除项事件event IGroupLayerEvents_ItemDeletedEventHandler ItemDeleted;}
///构建GroupLayerClass的子类// 构建GrouplayerClassEx类继承Esri的GroupLayer并实现自定义的IG肉pLayerEvents接口public class GroupLayerClassEx:GroupLayerClass,IGroupLayerEvents{#region IGroupLayerEvents 成员public event IGroupLayerEvents_ItemAddedEventHandler ItemAdded;public event IGroupLayerEvents_ItemDeletedEventHandler ItemDeleted;#endregion// 重写添加的方法public override void Add(ILayer layer){base.Add(layer);// 实现事件if (ItemAdded != null){ItemAdded(layer);}}// 重写清除的方法public override void Clear(){// 遍历图层实现项减少的事件if (ItemDeleted != null){ICompositeLayer pCompositeLayer = this as ICompositeLayer;for (int i = 0; i < pCompositeLayer.Count; i++){ILayer pCurrentLayer = pCompositeLayer.get_Layer(i);ItemDeleted(pCurrentLayer);}}base.Clear();}// 重写删除的方法public override void Delete(ILayer Layer){base.Delete(Layer);if (ItemDeleted != null){ItemDeleted(Layer);}}···其他IGroupLayer接口实现的方法和属性都要override一遍。···}
在地图控件事件中进行监听
private void axMapControl1_OnMapReplaced(object sender, IMapControlEvents2_OnMapReplacedEvent e){AxMapControl pAxMapControl = sender as AxMapControl;// 注册事件mEvent = pAxMapControl.ActiveView.FocusMap as IActiveViewEvents_Event;mEvent.ItemAdded += new IActiveViewEvents_ItemAddedEventHandler(Event_ItemAdded);mEvent.ItemDeleted += new IActiveViewEvents_ItemDeletedEventHandler(Event_ItemDeleted); }private void Event_ItemAdded(object Item){if (Item is IGroupLayer){IGroupLayerEvents pIGroupLayerEvents = Item as IGroupLayerEvents;if (pIGroupLayerEvents != null){pIGroupLayerEvents.ItemAdded += new IGroupLayerEvents_ItemAddedEventHandler(Event_ItemAdded);pIGroupLayerEvents.ItemDeleted += new IGroupLayerEvents_ItemDeletedEventHandler(Event_ItemDeleted);}}}