在Engine的工具(ITool)里:

OnClick事件处理函数中:

首先需要获取一个图层,作为Snapping的参照,

IFeatureLayer targetLayer

然后声明一个IMovePointFeedBack作为鼠标移动时捕捉点的显示:

IMovePointFeedback m_pMovePtFeed = new MovePointFeedback();  mFeedback = (IDisplayFeedback)m_pMovePtFeed;  ISimpleMarkerSymbol simpleMarkerSymbol = new SimpleMarkerSymbolClass();  IRgbColor pRGBColor = new RgbColorClass();  pRGBColor.Red = 0;  pRGBColor.Green = 0;  pRGBColor.Blue = 0;  simpleMarkerSymbol.Color = pRGBColor;  simpleMarkerSymbol.Size = 3;  simpleMarkerSymbol.Style = ESRI.ArcGIS.Display.esriSimpleMarkerStyle.esriSMSSquare;  ISymbol symbol = simpleMarkerSymbol as ISymbol;  symbol.ROP2 = esriRasterOpCode.esriROPNotXOrPen;  //symbol.ROP2 = esriRasterOpCode.;  m_pMovePtFeed.Symbol = (ISymbol)simpleMarkerSymbol;

然后, 开始Feedback的显示(tmpPoint是指开始的点,其实影响不大,如果不想要源点在屏幕上的话,可以取一个在屏幕外的点):

m_pMovePtFeed.Display = mMapControl.ActiveView.ScreenDisplay; m_pMovePtFeed.Start(tmpPoint, tmpPoint);

在OnMouseMove事件中:

IPoint pPoint2 = null;  IPoint pPoint = pMap.ActiveView.ScreenDisplay.DisplayTransformation.ToMapPoint(x, y);  pPoint2 = Snapping(pPoint.X, pPoint.Y, targetLayer, pMap, 10);  if (pPoint2 == null)  pPoint2 = pPoint;  ((IMovePointFeedback)mFeedback).MoveTo(pPoint2);

其中Snapping函数即为最主要的查找函数,其功能为根据输入的点坐标在目标图层上查找最为相近的点(也即需要捕捉的点),返回该点,若没有找到则返回NULL,最后一个参数的含义是,在地图控件上,以多少个像素为单位在周边查找捕捉点.

public IPoint Snapping(double x, double y, IFeatureLayer iFeatureLyr, IMapControl3 axMapControl1,double snappingDis)  {      IPoint iHitPoint = null;      IMap iMap = axMapControl1.Map;      IActiveView iView = axMapControl1.ActiveView;      IFeatureClass iFClss = iFeatureLyr.FeatureClass;      IPoint point = new PointClass();      point.PutCoords(x, y);      double length = ConvertPixelsToMapUnits(axMapControl1.ActiveView, snappingDis);      ITopologicalOperator pTopo = point as ITopologicalOperator;      IGeometry pGeometry = pTopo.Buffer(length).Envelope as IGeometry;      ISpatialFilter spatialFilter = new SpatialFilterClass();      spatialFilter.GeometryField = iFeatureLyr.FeatureClass.ShapeFieldName;      spatialFilter.SpatialRel = esriSpatialRelEnum.esriSpatialRelIntersects;      spatialFilter.Geometry = pGeometry;      IFeatureCursor cursor = iFClss.Search(spatialFilter, false);      IFeature iF = cursor.NextFeature();      if (iF == null) return null;      IPoint iHitPt = new ESRI.ArcGIS.Geometry.Point();      IHitTest iHitTest = iF.Shape as IHitTest;      double hitDist = 0;      int partIndex = 0;      int vertexIndex = 0;      bool bVertexHit = false;      // Tolerance in pixels for line hits      double tol = ConvertPixelsToMapUnits(iView, snappingDis);      if (iHitTest.HitTest(point, tol, esriGeometryHitPartType.esriGeometryPartBoundary,  iHitPt, ref hitDist, ref partIndex, ref vertexIndex, ref bVertexHit))      {  iHitPoint = iHitPt;      }      //axMapControl1.ActiveView.Refresh();      return iHitPoint;  }  public double ConvertPixelsToMapUnits(IActiveView pActiveView, double pixelUnits)  {      double realWorldDisplayExtent;      int pixelExtent;      double sizeOfOnePixel;      pixelExtent = pActiveView.ScreenDisplay.DisplayTransformation.get_DeviceFrame().right - pActiveView.ScreenDisplay.DisplayTransformation.get_DeviceFrame().left;      realWorldDisplayExtent = pActiveView.ScreenDisplay.DisplayTransformation.VisibleBounds.Width;      sizeOfOnePixel = realWorldDisplayExtent / pixelExtent;      return pixelUnits * sizeOfOnePixel;  }

此时即可实现鼠标实时地捕捉目标图层上的对象,若需要获取当前位置的捕捉点时,则可以在相应事件(例如OnMouseDown或OnDbClick)中调用:

IPoint pPoint = ((IMovePointFeedback)mFeedback).Stop(); 

这时实时捕捉将会停止,若需要重新开始捕捉,则在之后调用这些语句即可:

 

//重新开始Snap  IPoint tmpPoint = new PointClass();  tmpPoint.PutCoords(pMap.Extent.XMin - 1, pMap.Extent.YMin - 1);  IMovePointFeedback m_pMovePtFeed = (IMovePointFeedback)mFeedback;  m_pMovePtFeed.Display = pMap.ActiveView.ScreenDisplay;  m_pMovePtFeed.Start(tmpPoint, tmpPoint);