Delphi+AO（2）

3. 地图的放大、缩小、漫游和全景显示
   在Mapcontrol控件的OnMouseDown事件里加入以下的代码：
   procedure TForm1.MapControlMouseDown(Sender: TObject; button, shift, x,
   y: Integer; mapX, mapY: Double);
   var
   envlp: IEnvelope;
   bIsEmpty: wordbool;
   begin
   //在Mapcontrol上按下鼠标左键后做拉框操作，实现地图放大功能
   if (Button = 1) and (Shift = 0) then
   begin
   MapControl.MousePointer := esriPointerZoomIn;
   envlp := MapControl.TrackRectangle;
   envlp.Get_IsEmpty(bIsEmpty);
   if not bIsEmpty then
   MapControl.Extent := envlp
   exit
   end;
   //按下Shift键的同时在Mapcontrol上按下鼠标左键在做点击操作，实现地图缩小功能
   if (Button = 1) and (Shift = 1) then
   begin
   MapControl.MousePointer := esriPointerZoomOut;
   envlp := MapControl.Extent;
   envlp.Expand(2,2,False);
   MapControl.Extent := envlp;
   exit;
   end;
   //在Mapcontrol上按下鼠标右键键后做拖动操作，实现地图漫游功能
   if (Button = 2) and (Shift = 0) then
   begin
   MapControl.MousePointer := esriPointerPanning;
   MapControl.Pan;
   MapControl.MousePointer := esriPointerPan;
   exit;
   end;
   end;

在Mapcontrol控件的OnDoubleClick事件里加入以下的代码：
procedure TForm1.MapControl1DoubleClick(Sender: TObject; button, shift, x,
y: Integer; mapX, mapY: Double);
begin
// 在Mapcontrol上双击，实现地图全景显示功能
MapControl1.Extent := MapControl1.FullExtent;
end;

4. 地图上添加点状图形标记的功能
   先声明两个窗体Form1的私有变量：
   F_MultiPoint: IMultiPoint;
   F_Pts: IPointCollection;
   再在窗体Form1的OnCreate事件里加入以下的代码：
   F_MultiPoint := CoMultiPoint.Create as IMultiPoint;
   F_Pts := F_MultiPoint as IPointCollection;
   然后给Form1窗体添加一个的用于添加点状图形标记的全局的方法DrawPoint，
   实现代码如下：
   procedure TForm1.DrawPoint;
   var
   pt_cnt,i: integer;
   sym: ICharacterMarkerSymbol;
   pt: IPoint;
   ft: TFont;
   oleft: variant;
   ScreenDisplay: IScreenDisplay;
   ActiveView: IActiveView;
   begin
   ActiveView := MapControl.ActiveView;
   ActiveView.Get_ScreenDisplay(ScreenDisplay);
   F_Pts.Get_PointCount(pt_cnt);
   if pt_cnt > 0 then
   begin
   ScreenDisplay.StartDrawing(0,0);
   for i := 0 to pt_cnt-1 do
   begin
   F_Pts.Get_Point(i,pt);
   sym := coCharacterMarkerSymbol.Create as ICharacterMarkerSymbol;
   sym.Set_Size(30);
   ft := TFont.Create;
   ft.Size := 40;
   ft.Name := 'Wingdings';
   oleft := FontToOleFont(ft);
   sym.Set_Font(IFontDisp(IDispatch(oleft)));
   sym.Set_CharacterIndex(i+33);
   ScreenDisplay.SetSymbol(sym as ISymbol);
   ScreenDisplay.DrawPoint(pt);
   end;
   ScreenDisplay.FinishDrawing;
   end;
   end;

然后在Mapcontrol控件的OnMouseDown事件里加入以下的代码：
//按下Shift键的同时在Mapcontrol上按下鼠标右键在做点击操作，
//实现在地图上添加点状图形标记的功能
if (Button = 2) and (Shift = 1) then
begin
pt := mapcontrol1.ToMapPoint(x,y);
F_Pts.AddPoint(pt,EmptyParam,EmptyParam);
DrawPoint;
exit;
end;
最后，在Mapcontrol控件的OnAfterDraw事件里加入以下的代码：
procedure TForm1.MapControlAfterDraw(Sender: TObject; const
display: IDisplay; phase: TOleEnum);
begin
DrawPoint; //用于刷新添加在地图上的点状图形标
end;
这样，一个包含了一些简单的GIS功能的应用程序就完成了（按F9可以运行）。