MapObejcts组件应用设计(几何对象).doc

1. Point对象2. Line及Polygon对象1. 图形坐标数据2. Points集合与Parts集合3. 几何对象的运算1. IsPointIn2. GetCrossings3.4. Intersect5. Difference6. Xor7. Buffer4. 动态分段1. 点事件(PointEvents)2. 线事件(LineEvent)3. 线的节点(Vertex)路程4. 动态分段样例MapObjects2可以处理的几何元素有Point 、Line、 Polygon、 Circle、 Rectangle,每种元素定义成一个对象。这些对象统称为Shape,但没有定义Shape对象。除了Point以外，其它四种都提供了交互式输入方法：TrackLine 、TrackPolygon、 TrackCircle、 TrackRectangle。2.5.1 Point对象Point是最简单的对象，语句Dim pt As New MapObjects2.Pointpt.X = 30342pt.Y = 43535建立了一个Point实例。2.5.2 Line及Polygon对象1图形坐标数据在MapObjects2中，Line与Polygon图形都用Point的有序集合的集合定义，称为parts，Point的有序集合定义一条折线，称为part,part的集合命名为Parts。只有一条折线的Line或Polygon实例的Parts集合中仅含有一个part。在Line中part的首尾两点不同，在Polygon中part的首尾两点用一个Point表示。下面这段程序取自附属盘中的样例GeoData中的MouseDown事件过程，程序先根据鼠标位置查出一个省区，然后将省区多边形的坐标串加入到List1控件中。Dim recs As MapObjects2.Recordset 查询结果记录集Dim curX As Single, curY As Single 鼠标光标位置坐标Case “显示选择的多边形坐标数据”Dim pt As MapObjects2.PointDim dist As DoubleSet pt = Map1.ToMapPoint(curX, curY) 根据屏幕坐标建立point实例dist = 1000Set recs = Map1.Layers(“china”).SearchByDistance(pt, dist, “”) 按距离查询If recs.EOF Then Exit Sub在列表框中显示省界坐标”Dim shp As PolygonDim pts As MapObjects2.PointsDim i As IntegerDim j As IntegerSet shp = recs(“Shape”).ValueMe.List1.ClearMe.List1.AddItem “Parts.Count = “ & shp.Parts.CountMe.List1.AddItem recs.Fields(“Name”) + “省界坐标”For j = 0 To shp.Parts.Count-1Set pts = shp.Parts(j)For i = 0 To pts.Count - 1Me.List1.AddItem (Str(pts.Item(i).X) & “ “ & Str(pts.Item(i).Y)Next iNext jMap1.Refresh 触发Map1_AfterTrackingLayerDraw事件过程，绘制查询结果图End Select2 Points集合与Parts集合在Polygon及Line对象中，Points是点的集合，Parts是Points的集合。以下是集合上的常用操作：Dim poly As MapObjects2.PolygonDim pts As MapObjects2.PointsSet poly = Map1.TrackPolygon 鼠标跟踪绘制一个多边形Set pts = poly.Parts.Item(0) 获得多边形中Points集合的引用pts.Remove pts.Count 1 删除多边形上的最后一点Dim pt AsNew MapObjects2.Pointpt.X = 2300pt.Y = 4500pts.Set 2 , pt 替换pts集合中的点pts.Item(2)pts.Reverse 改变pts中点的排列方向在Polygon对象中，Points集合中点的排列方向赋予了特殊的含义。简单Polygon边界Points点按顺时针方向排列。含有岛区的复合Polygon的外围边界线点按顺时针方向排列，内部岛区边界线点按逆时针方向排列。Parts集合是不可创建对象，Polygon与Line的Parts属性也是只读的。在创建Polygon或Line对象的实例同时创建了Parts实例,且用Parts属性引用Parts实例。可按如下步骤建立一个完整的Polygon实例：1创建一个Polygon对象实例。2创建Points对象实例。3创建Point对象实例,设置它的X、Y属性值，用Pionts.Add方法添加到Points实例中。4重复步骤3,将所有的点加入到Points实例中。5用Polygon.Parts.Add方法将Points实例加入到Parts属性中。单Part的Polygon用上述5步即可建立。 对于多Part的Polygon重复步骤5。同理可以建立Line实例。2.5.3几何对象的运算MapObject2 的几何对象共有6种,符号常量由枚举表ShapeTypeConstants定义如下符号常量值对象名moShapeTypePoint21PointmoShapeTypeLine22LinemoShapeTypePolygon23PloygonmoShapeTypeMultipoint24PointsmoShapeTypeRectangle25RectanglemoShapeTypeEllipse26Ellipse六种对象的父对象都是Object。例：判断几何对象的类型。Dim ObjA As ObjectDim ObjPoint As New MapObjects2.PointDim ObjPolygon As New MapObjects2.PolygonSet ObjA = ObjPointIf ObjA.shapeType = moShapeTypePoint Then Debug.Print ObjA类型是PointSet ObjA = ObjPolygonIf ObjA.shapeType = moShapeTypePolygon Then Debug.Print objA的类型是Polygon 几何对象的运算在上表中6种对象的实例上进行，由实例的方法完成运算，运算数据来源于实例及实例方法中的参数。1 IsPointInFunction IsPointIn(pt As Point) As Boolean适用对象: Polygon, Rectangle，Ellipse这个方法判断点是否位于几何对象围成的区域中。例:Dim pt as New MapObjects2.Pointpt.X = 1200pt.Y = 2000if Not Map1.Extent.IsPointIn(pt) Then Map.Extent是Ractangle对象Map1.CenterAt pt.X, pt.Y 以pt为中心显示地图End If2 GetCrossingsFunction GetCrossings(Shape As Object) As Points适用对象: Point,Points,Line, Polygon, Rectangle这个函数计算两个几何图形的交点集合。例:Dim shape As New MapObjects2.LineDim aPoly As New MapObjects2.PolygonDim pts As MapObjects2.Points设置shape和aPoly的parts属性值Set pts = aPoly.GetCrossings(shape) 返回交点集合的引用3 Function Union(Shape As Object,Extent) As Object适用对象: Point, Points, Line, Polygon, Rectangle, Ellipse这个函数返回两个几何图形的并。Polygon和Rectangle都表示面，归为同一类类型。参与运算的两个对象应属于同一类型对象。例:Dim aPoly As MapObjects2.PolygonDim bPoly As MapObjects2.PolygonDim cPoly As MapObjects2.Polygon设置aPoly及bPoly的parts属性值Set cPoly = aPoly.Union(bPoly) 4 IntersectFunction Intersect(Shape As Object,Extent) As Object这个 函数返回两个几何图形的交。句法：Set resultShape = object.Intersect (Shape ,extent)object可以是： Point, Points, Line, Polygon, Rectangle, Ellipse 6 种对象Shape可以是： Point, Points, Line, Polygon, Rectangle, Ellipse 6 种对象resultShape的类型随object与Shape的组合而异，如下表所示resultShape的类型Shape objectPointPointsLinePolygonRectangleEllipsePointPointPointPointPointPointPointPointsPointPoint 或PointsPoint 或PointsPoint或PointsPoint 或PointsPoint 或PointsLinePointPoint 或PointsPoint 或PointsLineLineLinePolygonPointPoint 或PointsLinePolygonPolygong或RactanglePolygonRectanglePointPoint 或PointsLinePolygon或RactagleRactanglePolygon或RactangleEllipsePointPoint 或PointsLinePolygonPolygon或RactanglePolygon5 DifferenceFunction Difference(Shape As Object,Extent) As Object适用对象: Point, Points, Line, Polygon, Rectangle, Ellipse这个函数返回两个几何图形的差。例：Set cPoly = aPoly.Difference(bPoly)6 XorFunction Xor(Shape As Object,Extent) As Object适用对象: Point, Points, Line, Polygon, Rectangle, Ellipse这个函数返回两个几何图形的异或。例：Set cPoly = aPoly.Xor(bPoly)7 BufferFunction Buffer(distance As Object, Extent) As Object适用对象: Point, Points, Line, Polygon, Rectangle, EllipseBuffer函数返回边界距离调用对象为distance的Polygon。例：Dim aPoly As MapObjects2.PolygonDim aLine As New MapObjects2.Line设置aLine的Parts属性值Set aPloly = aLine.Buffer(120)在MapObjects2中，Buffer Intersect Difference Union及Xor方法使用整数坐标，具有较高的计算速度。为确保从浮点数转换到整数保持几何操作的一致性，建议使用Rectangle型的Extent参数，对所有的几何操作使用相同的Extent参数。若不使用参数Extent，对相同的Shape重复使用几何方法，不同次的结果图形的几何坐标可能会出现计算误差。如果在方法中没有使用Extent参数，Mapobjets2使用两个源Shape的外接矩形的并。例1 在跟踪层画两个Polygon 求它们的Xor,用不同的颜色在跟踪层显示源Polygon和结果Polygon。完整代码在XorPolygon样例目录中。主要代码如下：Dim shape1 As ObjectDim exclOr As BooleanPrivate Sub Form_Load() 设置PointEvents在跟踪层中得显示用的符号符号exclOr = FalseMap1.TrackingLayer.SymbolCount = 2With Map1.TrackingLayer.Symbol(0).SymbolType = moFillSymbol 面（区域).Style = moGrayFill 半透明填充.Color = moCyan.OutlineColor = moCyanEnd WithWith Map1.TrackingLayer.Symbol(1).SymbolType = moFillSymbol.Style = moGrayFill 半透明填充.Color = moMagenta.OutlineColor = moMagentaEnd WithEnd SubPrivate Sub Map1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single) 在Map1窗口中画两个Polygon 计算它们的 XORDim poly As New MapObjects2.PolygonDim eventLine As New MapObjects2.GeoEventSet poly = Map1.TrackPolygon 在Map1窗口中画PolygonSet eventLine = Map1.TrackingLayer.AddEvent(poly, 0) 在跟踪层中显示PolyCall doXor(poly)End SubPrivate Sub doXor(shape As Object) 计算两个Polygon的XORIf Not exclOr Then 画第一个Polygon时保存到Shape1中Set shape1 = shapeexclOr = TrueElseIf exclOr Then 画完第而个Polygon后则计算它们的 XORDim xorShape As ObjectDim xorEvent As New MapObjects2.GeoEventSet xorShape = shape1.Xor(shape, Map1.FullExtent) 计算两个Polygon的XorSet xorEvent = Map1.TrackingLayer.AddEvent(xorShape, 1) 加入到跟踪层中Set shape1 = NothingexclOr = FalseEnd IfEnd Sub习题1 编写程序实现样例1的功能。2 以习题1的代码为基础，写出Intersect程序，在程序中判断Intersect函数的返回结果的Shape类型。2.5.4动态分段动态分段在Line对象上操作，是Line对象的特有方法操作的结果。在MapObjects2中Line表示有向折线，折线的折点称为Vertex(节点),折线的始末点称为Node(结点)。以始结点为度量起点,每个节点都有一个沿着折线的路程值，用路程值确定点在折线上的位置，给定的路程值确定了折线上的唯一点。1点事件(PointEvents)Line对象几何图形上的任意一点称为PointEvent，PointEvent专用于程序设计，可在程序运行中动态创建，动态改变位置，是动态的Point实例。例：在长度为500的线实例aLine上创建距始点路程为400的点事件。Dim ptsEvents As MapObjects2.PointsSet ptsEvents = aLine.ReturnPointEvents(400) 05002线事件(LineEvent)从Line对象几何图形上截取的任意一条线段称为LineEvent(线事件)，LineEvent是动态创建的线实例,用线的始末点在原Line上的路程确定截取位置。例：在长度为500的Line实例aLine上，创建始点路程200终点路程400的线事件。Dim lineEvent as MapObjects2.LineSet lineEvent = aLine.ReturnLineEvent(200,400)3线的节点(Vertex)路程Line对象实例上的节点距始结点(Node)的路程作为线的几何属性常用于最佳路径分析及网络分析，为此MapObjects.Line对象提供了两个方法：(1) Sub SetMeasuresAsLength()此方法为线的节点的Measure属性赋路程值, 路程值用地图的数据坐标计算，是地面上的实际路程。例：在长度为500的线实例aLine上设置节点的Measure(路程)属性值aLine.SetMeasuresAsLength080280310500180各节点的Measure属性值如下：从上例可见，aLine的始末结点也算作节点。(2) Sub SetMeasures(StartValue As Double,EndValue As Double)此方法用StartValue作为始节点的路程值，用EndValue作为末节点的路程值，在这两个值之间按新旧路程的比例插值作为中间节点的路程值,将计算结果赋给节点的Measure属性。执行此函数之前可执行也可不执行SetMeasuresAsLength函数。例：对上例中aLine实例重新设置节点的路程属性值，使得始节点的路程值为1,末节点的路程值为251,中间节点路程值按新旧路程值比例计算。aLine.SetMeasurs(1,251)141141156251914动态分段样例在MapObjects中，点事件将给定的线动态分为两段，称为动态分段(Dynamic Segmentation)。分段只是视觉上的效果，并未对线进行实际分割。动态分段函数不会更改线的节点坐标值。例1 用鼠标在地图窗口中输入一点，找出最近的一条线，在线上分别使用3个Measure函数，显示出每个Measuer 函数设置的线的各个节点的Measure值。完整样例在SetMeasuer目录中Private Sub Map1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)Dim pt As MapObjects2.PointDim recs As New MapObjects2.RecordsetSet pt = Map1.ToMapPoint(X, Y) 转换(X,Y)成地图数据坐标系下的坐标Set recs = Map1.Layers(0).SearchByDistance(pt, Map1.ToMapDistance(150), ) 如果找到了一条线,则提取它的 shape 字段值储存在 oLine 变量中, 设置 measures 在列表框中显示oLine上的 的各个节点的Measure值。If Not recs.EOF ThenDim oLine As New MapObjects2.LineDim pointMeasuer As DoubleSet oLine = recs(Shape).ValueMap1.TrackingLayer.ClearEventsMap1.TrackingLayer.AddEvent oLine, 0List1.ClearList2.ClearList3.ClearDim vertices As New MapObjects2.PointsDim i As IntegeroLine.SetMeasuresAsLengthpointMeasuer = oLine.ReturnMeasure(pt)List1.AddItem 鼠标点的 Measure: & pointMeasuerList1.AddItem 节点的 Measure:For Each vertices In oLine.PartsFor i = 0 To vertices.Count - 1List1.AddItem vertices(i).MeasureNext iNext verticesoLine.SetMeasures 0, 100pointMeasuer = oLine.ReturnMeasure(pt)List2.AddItem 鼠标点的 Measure: & pointMeasuerList2.AddItem 节点的 Measure:For Each vertices In oLine.PartsFor i = 0 To vertices.Count - 1List2.AddItem vertices(i).MeasureNext iNext verticesoLine.OffsetMeasures 50pointMeasuer = oLine.ReturnMeasure(pt)List3.AddItem 鼠标点的 Measure: & pointMeasuerList3.AddItem 节点的 Measure:For Each vertices In oLine.PartsFor i = 0 To vertices.Count - 1List3.AddItem vertices(i).MeasureNext iNext verticesEnd IfEnd Sub例2：在地图窗口中用鼠标左键输入一点，在Map1.Layers(“Road”)图层中找出与输入点距离最近的线，在找到的线上创建与输入点距离最近的点(点事件)。在跟踪层中用红色显示点事件。样例在PntEnt.vbp工程中，从中摘取的程序如下:Private Sub Form_Load()省略的其它语句设置PointEven