C# 调用 Google Earth Com API开发（四）

本篇继续介绍Google Earth COM API开发的基础知识，相对第三篇的改进如下：

1)增加鼠标滚轮支持，可以实现放大、缩小。此功能利用上一篇提供的HookAPI.dll实现

2)读取PlaceMarks（Google Earth界面中的位置）并显示、隐藏

3)读取所有图层，显示并隐藏

下面，继续放代码：

1、鼠标滚轮事件，实现放大、缩小

   1: ...

   2: // 放大

   3: private const long ZoomIn = 0x00780000;

   4: // 缩小

   5: private const long ZoomOut = 0xFF880000;

   6: ...

   7: mouseHook.MouseWheel += new MouseEventHandler(mouseHook_MouseWheel);

   8: ...

   9: /// <summary>

  10: /// 鼠标钩子。鼠标滚动事件

  11: /// </summary>

  12: /// <param name="sender"></param>

  13: /// <param name="e"></param>

  14: void mouseHook_MouseWheel(object sender, MouseEventArgs e)

  15: {

  16:     IntPtr hWnd = NativeMethods.WindowFromPoint(e.Location);

  17:     if (hWnd == this.GeRenderHWnd)

  18:     {

  19:         Point point = this.Control.PointToClient(e.Location);

  20:         // 如果鼠标位置在控件内部，则说明鼠标在GoogleEarth视图范围内进行了滚动

  21:         if (this.Control.ClientRectangle.Contains(point))

  22:         {

  23:             NativeMethods.PostMessage(GeRenderHWnd, (int)WM_MOUSE.WM_MOUSEWHEEL, e.Delta == 120 ? ZoomIn : ZoomOut, 0);

  24:         }

  25:     }

  26: }

2、读取PlaceMarks

Google Earth COM API中提供了两个读取PlaceMarks的函数。一个是GetTemporaryPlaces()，用来读取临时位置；另一个是GetMyPlaces()，用来读取自定义位置，即GoogleEarth中显示的“我的位置”。呵呵

   1: ...

   2: /// <summary>

   3: /// 显示位置“PlaceMarks”。位置分为两种，一种时TemporaryPlaces，另一种为MyPlaces

   4: /// </summary>

   5: protected void ShowPlaces()

   6: {

   7:     Thread.Sleep(500);

   8:     // 获取MyPlaces

   9:     FeatureGE myPlace = GeApp.GetMyPlaces();

  10:     // 获取临时位置

  11:     FeatureGE temporaryPlace = GeApp.GetTemporaryPlaces();

  12:     // 

  13:     List<FeatureGE> places = new List<FeatureGE>();

  14:     places.Add(myPlace);

  15:     places.Add(temporaryPlace);

  16:  

  17:     // 获取工具面板

  18:     GEToolPad toolPad = GetToolPad();

  19:     // 显示所有位置

  20:     toolPad.ShowPlaces(places);

  21: }

  22: ...

  23: /// <summary>

  24: /// 显示所有PlaceMarks（位置）

  25: /// </summary>

  26: /// <param name="places"></param>

  27: public void ShowPlaces(List<FeatureGE> places)

  28: {

  29:     if (this.InvokeRequired)

  30:     {

  31:         Action method = delegate {

  32:             InternalShowPlaces(places);

  33:         };

  34:  

  35:         try

  36:         {

  37:             this.Invoke(method);

  38:         }

  39:         catch { }

  40:     }

  41:     else

  42:     {

  43:         InternalShowPlaces(places);

  44:     }

  45: }

  46: /// <summary>

  47: /// 显示所有PlaceMarks（位置）。被ShowPlaces函数调用

  48: /// </summary>

  49: /// <param name="places"></param>

  50: protected void InternalShowPlaces(List<FeatureGE> places)

  51: {

  52:     this.tvPlaces.Nodes.Clear();

  53:  

  54:     if (places == null || places.Count <= 0)

  55:         return;

  56:  

  57:     foreach (FeatureGE place in places)

  58:     {

  59:         TreeNode node = new TreeNode(place.Name);

  60:         node.Checked = place.Visibility > 0;

  61:         node.Tag = place;

  62:  

  63:         ShowChildrenPlaces(place, node);

  64:  

  65:         node.Expand();

  66:  

  67:         this.tvPlaces.Nodes.Add(node);

  68:     }

  69: }

  70: /// <summary>

  71: /// 显示指定PlaceMark的子PlaceMark

  72: /// </summary>

  73: /// <param name="place">父PlaceMark</param>

  74: /// <param name="node">父节点</param>

  75: protected void ShowChildrenPlaces(FeatureGE place, TreeNode node)

  76: {

  77:     FeatureCollectionGE places = place.GetChildren();

  78:  

  79:     foreach (FeatureGE child in places)

  80:     {

  81:         TreeNode tn = new TreeNode(child.Name);

  82:         tn.Checked = child.Visibility > 0;

  83:         tn.Tag = child;

  84:  

  85:         ShowChildrenPlaces(child, tn);

  86:  

  87:         node.Nodes.Add(tn);

  88:     }

  89: }

3、读取图层

   1: ...

   2: /// <summary>

   3: /// 显示图层

   4: /// </summary>

   5: protected void ShowLayers()

   6: {

   7:     Thread.Sleep(500);

   8:     // 获取所有图层信息

   9:     FeatureCollectionGE layers = GeApp.GetLayersDatabases();

  10:     // 获取工具面板

  11:     GEToolPad toolPad = GetToolPad();

  12:     // 显示所有图层

  13:     toolPad.ShowLayers(layers);

  14: }

  15: ...

  16: /// <summary>

  17: /// 将给定的图层集合显示在“图层”选项卡的树形控件中

  18: /// </summary>

  19: /// <param name="layers">图层集合</param>

  20: public void ShowLayers(FeatureCollectionGE layers)

  21: {

  22:     if (this.InvokeRequired)

  23:     {

  24:         Action method = delegate {

  25:             InternalShowLayers(layers);

  26:         };

  27:         try

  28:         {

  29:             this.Invoke(method);

  30:         }

  31:         catch { }

  32:     }

  33:     else

  34:     {

  35:         InternalShowLayers(layers);

  36:     }

  37: }

  38: /// <summary>

  39: /// 将给定的图层集合显示在“图层”选项卡的树形控件中.被公共函数ShowLayers调用

  40: /// </summary>

  41: /// <param name="layers"></param>

  42: protected void InternalShowLayers(FeatureCollectionGE layers)

  43: {

  44:     this.tvLayers.Nodes.Clear();

  45:  

  46:     if (layers == null || layers.Count <= 0)

  47:     {

  48:         return;

  49:     }

  50:  

  51:     foreach (FeatureGE layer in layers)

  52:     {

  53:         TreeNode node = new TreeNode(layer.Name);

  54:         node.Checked = layer.Visibility > 0;

  55:         node.Tag = layer;

  56:  

  57:         ShowChidrenLayers(layer, node);

  58:  

  59:         node.Expand();

  60:  

  61:         this.tvLayers.Nodes.Add(node);

  62:     }

  63: }

  64: /// <summary>

  65: /// 显示指定图层的子图层

  66: /// </summary>

  67: /// <param name="layer">当前图层</param>

  68: /// <param name="node">当前节点</param>

  69: protected void ShowChidrenLayers(FeatureGE layer, TreeNode node)

  70: {

  71:     FeatureCollectionGE layers = layer.GetChildren();

  72:  

  73:     foreach (FeatureGE child in layers)

  74:     {

  75:         TreeNode tn = new TreeNode(child.Name);

  76:         tn.Checked = child.Visibility > 0;

  77:         tn.Tag = child;

  78:  

  79:         ShowChidrenLayers(child, tn);

  80:  

  81:         node.Nodes.Add(tn);

  82:     }

  83: }

呵呵，代码很简单。按照此代码修改第三篇的源程序就可以实现本篇的功能了。