关于GMAP.NET地图控件在地图上操作的例子很多，但是关于画圆形的描述很少，我找到了GMAP官方的例子并在此基础上进行了部分的改动，实现了对GMAP地图控件的画圆操作。
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6 using System.Drawing;
7 using System.Runtime.Serialization;
8 using GMap.NET;
9 using GMap.NET.WindowsForms;
10
11 namespace tgmap
12 {
13 #if !PocketPC
14 [Serializable]
15 public class GMapMarkerCircle : GMapMarker, ISerializable
16 #else
17 public class GMapMarkerCircle : GMapMarker
18 #endif
19 {
20 /// <summary>
21 /// In Meters 用米数确定圆
22 /// </summary>
23 public int Radius;
24
25 /// <summary>
26 /// 用两个点确定圆
27 /// </summary>
28 public PointLatLng P2;
29
30 /// <summary>
31 /// 是否用米数确定圆
32 /// </summary>
33 public bool IsMeter = true;
34
35
36 /// <summary>
37 /// specifies how the outline is painted
38 /// </summary>
39 [NonSerialized]
40 #if !PocketPC
41 public Pen Stroke = new Pen(Color.FromArgb(155, Color.MidnightBlue));
42 #else
43 public Pen Stroke = new Pen(Color.MidnightBlue);
44 #endif
45
46 /// <summary>
47 /// background color
48 /// </summary>
49 [NonSerialized]
50 #if !PocketPC
51 public Brush Fill = new SolidBrush(Color.FromArgb(155, Color.AliceBlue));
52 #else
53 public Brush Fill = new System.Drawing.SolidBrush(Color.AliceBlue);
54 #endif
55
56 /// <summary>
57 /// is filled
58 /// </summary>
59 public bool IsFilled = true;
60
61 public GMapMarkerCircle(PointLatLng p)
62 : base(p)
63 {
64 Radius = 0; // 0m
65 P2 = p;
66 IsHitTestVisible = false;
67 }
68
69 public override void OnRender(Graphics g)
70 {
71 if (!IsMeter)
72 Radius = (int)Overlay.Control.MapProvider.Projection.GetDistance(Position, P2) * 1000;
73
74 int R = (int)((Radius) / Overlay.Control.MapProvider.Projection.GetGroundResolution((int)Overlay.Control.Zoom, Position.Lat)) * 2;
75
76 if (IsFilled)
77 {
78 g.FillEllipse(Fill, new System.Drawing.Rectangle(LocalPosition.X - R / 2, LocalPosition.Y - R / 2, R, R));
79 }
80 g.DrawEllipse(Stroke, new System.Drawing.Rectangle(LocalPosition.X - R / 2, LocalPosition.Y - R / 2, R, R));
81 }
82
83 public override void Dispose()
84 {
85 if (Stroke != null)
86 {
87 Stroke.Dispose();
88 Stroke = null;
89 }
90
91 if (Fill != null)
92 {
93 Fill.Dispose();
94 Fill = null;
95 }
96
97 base.Dispose();
98 }
99
100 public bool IsInside(PointLatLng p)
101 {
102 return (int)Overlay.Control.MapProvider.Projection.GetDistance(Position, p) * 1000 < Radius;
103 }
104
105 #if !PocketPC
106
107 #region ISerializable Members
108
109 void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
110 {
111 base.GetObjectData(info, context);
112
113 // TODO: Radius, IsFilled
114 }
115
116 protected GMapMarkerCircle(SerializationInfo info, StreamingContext context)
117 : base(info, context)
118 {
119 // TODO: Radius, IsFilled
120 }
121
122 #endregion
123
124 #endif
125 }
126 }
里面描述了两种画圆的方法，一种是根据半径（米）和Marker的Position来画圆，一种是根据Marker的Position和另外一个PointLatLng点来画圆。添加了IsInside方法来确认另一个点是否在圆内。第二种方法是为了实现鼠标点击拖动画圆，鼠标事件代码如下
1 private GMapOverlay circles = new GMapOverlay("circle"); //放置circle的图层
2 private GMapMarkerCircle drawingCircle = null; //正在画的circle
3 private bool IsDrawingCircle = false;
4
5 private void MapControl_MouseDown(object sender, MouseEventArgs e)
6 {
7 circles.Markers.Clear();
8 IsDrawingCircle = true;
9 drawingCircle = new GMapMarkerCircle(mapControl.FromLocalToLatLng(e.X, e.Y));
10 drawingCircle.IsMeter = false;
11 circles.Markers.Add(drawingCircle);
12
13 //polygons.Polygons.Clear();
14 //IsDrawingPolygon = true;
15 //startX = e.X;
16 //startY = e.Y;
17 //drawingPolygon = new GMapPolygon(new List<PointLatLng>() { mapControl.FromLocalToLatLng(e.X,e.Y)}, "polygon");
18 //polygons.Polygons.Add(drawingPolygon);
19 }
20
21 private void MapControl_MouseUp(object sender, MouseEventArgs e)
22 {
23 IsDrawingCircle = false;
24 int count = 0;
25 markersOverlay.Markers.ToList().ForEach(ma=> {
26 if (drawingCircle.IsInside(ma.Position))
27 {
28 count++;
29 }
30 });
31 MessageBox.Show("区域内一共有" + count + "个marker(s)");
32
33 //IsDrawingPolygon = false;
34 //int count = 0;
35 //markersOverlay.Markers.ToList().ForEach(ma => {
36 // if (drawingPolygon.IsInside(ma.Position))
37 // {
38 // count++;
39 // }
40 //});
41 //MessageBox.Show("区域内一共有" + count +"个marker(s)");
42 }
43
44 private void MapControl_MouseMove(object sender, MouseEventArgs e)
45 {
46 if (IsDrawingCircle)
47 {
48 drawingCircle.P2 = mapControl.FromLocalToLatLng(e.X,e.Y);
49 mapControl.UpdateMarkerLocalPosition(drawingCircle);
50 mapControl.Refresh();
51 }
52
53 //if (IsDrawingPolygon)
54 //{
55 // drawingPolygon.Points.Clear();
56 // drawingPolygon.Points.Add(mapControl.FromLocalToLatLng(startX,startY));
57 // drawingPolygon.Points.Add(mapControl.FromLocalToLatLng(startX, e.Y));
58 // drawingPolygon.Points.Add(mapControl.FromLocalToLatLng(e.X, e.Y));
59 // drawingPolygon.Points.Add(mapControl.FromLocalToLatLng(e.X, startY));
60 // mapControl.UpdatePolygonLocalPosition(drawingPolygon);
61 // mapControl.Refresh();
62 //}
63 }
注释的代码是我当初写拖动画矩形的部分，最终实现了鼠标放开后自动数出所画区域内Marker的数量，其实以后也可以对所有区域内的Marker进行进一步操作。
测试结果如下：
时间： 2024-11-08 05:15:36