PIE属性表多字段的文本绘制

　　最近研究了PIE SDK文本元素的绘制相关内容，因为在我们的开发中，希望可以做到在打开一个Shp文件后，读取到属性表的所有字段，然后可以选择一些需要的字段，将这些字段的所有要素值的文本，绘制到shp图中相应的要素位置上。

　　我主要是通过PIE的官方博文（https://www.cnblogs.com/PIESat/p/10172166.html）进行学习的，并在技术员姐姐的帮助下，最后成功的将文本绘制于图上。

结果如下图所示：

　　先打开一张属性表字段不为空Shp文件

　　读取shp的属性表中的所有字段，选取需要绘制在图上的字段

　　将所选的字段的值绘制到相应的要素的位置上

　　开发环境：vs2013 framework4

代码如下：

　　在子窗口的构造函数中，遍历当前shp文件属性表的所有字段，并设置默认好默认字体样式

  #region 构造函数
         public FeaturesShow(IFeatureDataset featureDataset)
         {
             InitializeComponent();
             m_featureDataset = featureDataset;
             IFeature feature = m_featureDataset.GetNextFeature();
             for (int i = ; i < feature.GetFieldCount(); i++)
             {
                 string fieldname = feature.GetFieldName(i);
                 this.listBox1.Items.Add(fieldname);
             }
             //默认字体
             FontDlg.Font = new Font("Calibri", , FontStyle.Bold);
             FontDlg.Color = Color.Chartreuse;
         }
    #endregion

　　点击了子窗体的确定后，返回得到已选择的字段名，和设置的字体样式，并在图上进行绘制

         private void 文本绘制ToolStripMenuItem_Click(object sender, EventArgs e)
         {
             if (mapControl1.ActiveView.CurrentLayer == null)
                 return;
             IFeatureLayer featurelayer = mapControl1.ActiveView.CurrentLayer as IFeatureLayer;
             if (featurelayer == null)
                 return;
 
             //清除图上已绘制的元素
             mapControl1.ActiveView.GraphicsContainer.DeleteAllElements();
             //获得要读取的数据，传入子窗体
             IFeatureDataset featureDataset = featurelayer.FeatureClass.GetFeatureDataset();
             FeaturesShow frm = new FeaturesShow(featureDataset);
             frm.ShowDialog();       //通过窗口来选择需要展示在图上的特征值
             if (frm.DialogResult == DialogResult.OK)
             {
                 //符号设置
                 FontDialog m_FontDlg = frm.m_FontDlg;
                 ITextSymbol textSymbol = new TextSymbol();
                 textSymbol.Color = m_FontDlg.Color;
                 textSymbol.Font = m_FontDlg.Font;
                 textSymbol.Size = m_FontDlg.Font.Size;              
 
                 int m_FeatureCount = frm.m_FeatureCount;
                 string[] m_Fieldname=frm.m_Fieldname;
                 int[] index = new int[m_FeatureCount+];
                 IFields fields = featureDataset.GetFields();
                 index[] = ;
                 for (int i = ; i < m_FeatureCount+;i++ )
                 {
                     index[i] = fields.GetFieldIndex(m_Fieldname[i-]);
                 }
                 IFeature feature = featureDataset.GetFeature();
                 while (feature != null)
                 {
                     ////取左上角坐标值
                     IPolygon polygon = new PIE.Geometry.Polygon();
                     polygon = feature.Geometry as IPolygon;
                     IPointCollection poly = polygon as IPointCollection;
                     IPoint point = poly.GetPoint();
                     //创建文本元素实例对象
                     ITextElement textElement = new PIE.Carto.TextElement();
                     textElement.Geometry = point as IGeometry;
                     textElement.Symbol = textSymbol;
 
                     for(int i=;i<m_FeatureCount+;i++)
                     {
                         string strValue = "";
                         if (feature.IsValueNull(index[i]) == false)
                         {
                             strValue = m_Fieldname[i-] + ":" + feature.GetValue(index[i]).ToString() + "\r\n";
                             textElement.Text = textElement.Text+strValue;
                         }
                     }
                     if(textElement.Text!="")
                     {
                         string strID = fields.GetFieldName() + ":" + feature.GetValue(index[]).ToString() + "\r\n";
                         textElement.Text = strID + textElement.Text;
                         mapControl1.ActiveView.GraphicsContainer.AddElement(textElement);
                     }
                     feature = featureDataset.GetNextFeature();
                 }
                 mapControl1.PartialRefresh(ViewDrawPhaseType.ViewAll);
             }
         }

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