DataGridView多維表頭的實現方法

背景

對于.NET 原本提供的DataGridView控件，制作成如下形式的表格是毫無壓力的。

但是如果把表格改了一下，變成如下形式

傳統的DataGridView就做不到了，如果擴展一下還是行的，有不少網友也擴展了DataGridView控件，不過有些也只能制作出二維的表頭。或者使用第三方的控件，之前也用過DevExpress的BoundGridView。不過在沒有可使用的第三方控件的情況下，做到下面的效果，就有點麻煩了。

那得自己擴展了，不過最后還是用了一個控件庫的報表控件，Telerik的Reporting。不過我自己還是擴展了DataGridView，使之能制作出上面的報表。

準備

學習了一些網友的代碼，原來制作這個多維表頭都是利用GDI+對DataGirdView的表頭進行重繪。

用到的方法包括

Graphics.FillRectangle //填充一個矩形

Graphics.DrawLine //畫一條線

Graphics.DrawString  //寫字符串

此外為了方便組織表頭，本人還定義了一個表頭的數據結構 HeaderItem 和 HeaderCollection 分別作為每個表頭單元格的數據實體和整個表頭的集合。

HeaderItem的定義如下

代碼如下:
public class HeaderItem
     {
         private int _startX;//起始橫坐標
         private int _startY;//起始縱坐標
         private int _endX; //終止橫坐標
         private int _endY; //終止縱坐標
         private bool _baseHeader; //是否基礎表頭

         public HeaderItem(int startX, int endX, int startY, int endY, string content)
         {
             this._endX = endX;
             this._endY = endY;
             this._startX = startX;
             this._startY = startY;
             this.Content = content;
         }

         public HeaderItem(int x, int y, string content):this(x,x,y,y,content)
         {

         }

         public HeaderItem()
         {

         }

         public static HeaderItem CreateBaseHeader(int x,int y,string content)
         {
             HeaderItem header = new HeaderItem();
             header._endX= header._startX = x;
             header._endY= header._startY = y;
             header._baseHeader = true;
             header.Content = content;
             return header;
         }

         public int StartX
         {
             get { return _startX; }
             set
             {
                 if (value > _endX)
                 {
                     _startX = _endX;
                     return;
                 }
                 if (value < 0) _startX = 0;
                 else _startX = value;
             }
         }

         public int StartY
         {
             get { return _startY; }
             set
             {
                 if (_baseHeader)
                 {
                     _startY = 0;
                     return;
                 }
                 if (value > _endY)
                 {
                     _startY = _endY;
                     return;
                 }
                 if (value < 0) _startY = 0;
                 else _startY = value;
             }
         }

         public int EndX
         {
             get { return _endX; }
             set
             {
                 if (_baseHeader)
                 {
                     _endX = _startX;
                     return;
                 }
                 if (value < _startX)
                 {
                     _endX = _startX;
                     return;
                 }
                 _endX = value;
             }
         }

         public int EndY
         {
             get { return _endY; }
             set
             {
                 if (value < _startY)
                 {
                     _endY = _startY;
                     return;
                 }
                 _endY = value;
             }
         }

         public bool IsBaseHeader
         {get{ return _baseHeader;} }

         public string Content { get; set; }
     }

設計思想是利用數學的直角坐標系，給每個表頭單元格定位并劃定其大小。與計算機顯示的坐標定位不同，這里的原點是跟數學的一樣放在左下角，X軸正方向是水平向右，Y軸正方向是垂直向上。如下圖所示

之所以要對GridView中原始的列頭進行特別處理，是因為這里的起止坐標和終止坐標都可以設置，而原始列頭的起始縱坐標（StartY）只能是0，終止橫坐標（EndX）必須與起始橫坐標（StartY）相等。

另外所有列頭單元格的集合HeaderCollection的定義如下
代碼如下:
public class HeaderCollection
     {
         private List<HeaderItem> _headerList;
         private bool _iniLock;

         public DataGridViewColumnCollection BindCollection{get;set;}

         public HeaderCollection(DataGridViewColumnCollection cols)
         {
             _headerList = new List<HeaderItem>();
             BindCollection=cols;
             _iniLock = false;
         }

         public int GetHeaderLevels()
         {
             int max = 0;
             foreach (HeaderItem item in _headerList)
                 if (item.EndY > max)
                     max = item.EndY;

             return max;
         }

         public List<HeaderItem> GetBaseHeaders()
         {
             List<HeaderItem> list = new List<HeaderItem>();
             foreach (HeaderItem item in _headerList)
                 if (item.IsBaseHeader) list.Add(item);
             return list;
         }

         public HeaderItem GetHeaderByLocation(int x, int y)
         {
             if (!_iniLock) InitHeader();
             HeaderItem result=null;
             List<HeaderItem> temp = new List<HeaderItem>();
             foreach (HeaderItem item in _headerList)
                 if (item.StartX <= x && item.EndX >= x)
                     temp.Add(item);
             foreach (HeaderItem item in temp)
                 if (item.StartY <= y && item.EndY >= y)
                     result = item;

             return result;
         }

         public IEnumerator GetHeaderEnumer()
         {
             return _headerList.GetEnumerator();
         }

         public void AddHeader(HeaderItem header)
         {
             this._headerList.Add(header);
         }

         public void AddHeader(int startX, int endX, int startY, int endY, string content)
         {
             this._headerList.Add(new HeaderItem(startX,endX,startY,endY,content));
         }

         public void AddHeader(int x, int y, string content)
         {
             this._headerList.Add(new HeaderItem(x, y, content));
         }

         public void RemoveHeader(HeaderItem header)
         {
             this._headerList.Remove(header);
         }

         public void RemoveHeader(int x, int y)
         {
            HeaderItem header= GetHeaderByLocation(x, y);
            if (header != null) RemoveHeader(header);
         }

         private void InitHeader()
         {
             _iniLock = true;
             for (int i = 0; i < this.BindCollection.Count; i++)
                 if(this.GetHeaderByLocation(i,0)==null)
                 this._headerList.Add(HeaderItem.CreateBaseHeader(i,0 , this.BindCollection[i].HeaderText));
             _iniLock = false;
         }
     }

這里仿照了.NET Frameword的Collection那樣定義了Add方法和Remove方法，此外說明一下那個 GetHeaderByLocation 方法，這個方法可以通過給定的坐標獲取那個坐標的HeaderItem。這個坐標是忽略了整個表頭合并單元格的情況，例如

上面這幅圖，如果輸入0，0 返回的是灰色區域，輸入2，1 或3，2 或 5，1返回的都是橙色的區域。

擴展控件

到真正擴展控件了，最核心的是重寫 OnCellPainting 方法，這個其實是與表格單元格重繪時觸發事件綁定的方法，通過參數 DataGridViewCellPaintingEventArgs 的 ColumnIndex 和 RowIndex 屬性可以知道當前重繪的是哪個單元格，于是就通過HeaderCollection獲取要繪制的表頭單元格的信息進行重繪，對已經重繪的單元格會進行標記，以防重復繪制。
代碼如下:
protected override void OnCellPainting(DataGridViewCellPaintingEventArgs e)
         {
             if (e.ColumnIndex == -1 || e.RowIndex != -1)
             {
                 base.OnCellPainting(e);
                 return;
             }
             int lev=this.Headers.GetHeaderLevels();
             this.ColumnHeadersHeight = (lev + 1) * _baseColumnHeadHeight;
             for (int i = 0; i <= lev; i++)
             {
                 HeaderItem tempHeader= this.Headers.GetHeaderByLocation(e.ColumnIndex, i);
                 if (tempHeader==null|| i != tempHeader.EndY || e.ColumnIndex != tempHeader.StartX) continue;
                 DrawHeader(tempHeader, e);
             }
             e.Handled = true;
         }

上面的代碼中，最初是先判斷當前要重繪的單元格是不是表頭部分，如果不是則調用原本的OnCellPainting方法。 e.Handled=true; 比較關鍵，有了這句代碼，重繪才能生效。

繪制單元格的過程封裝在方法DrawHeader里面

代碼如下:
private void DrawHeader(HeaderItem item,DataGridViewCellPaintingEventArgs e)
         {
             if (this.ColumnHeadersHeightSizeMode != DataGridViewColumnHeadersHeightSizeMode.DisableResizing)
                 this.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.DisableResizing;
             int lev=this.Headers.GetHeaderLevels();
             lev=(lev-item.EndY)*_baseColumnHeadHeight;

             SolidBrush backgroundBrush = new SolidBrush(e.CellStyle.BackColor);
             SolidBrush lineBrush = new SolidBrush(this.GridColor);
             Pen linePen = new Pen(lineBrush);
             StringFormat foramt = new StringFormat();
             foramt.Alignment = StringAlignment.Center;
             foramt.LineAlignment = StringAlignment.Center;

             Rectangle headRec = new Rectangle(e.CellBounds.Left, lev, ComputeWidth(item.StartX, item.EndX)-1, ComputeHeight(item.StartY, item.EndY)-1);
             e.Graphics.FillRectangle(backgroundBrush, headRec);
             e.Graphics.DrawLine(linePen, headRec.Left, headRec.Bottom, headRec.Right, headRec.Bottom);
             e.Graphics.DrawLine(linePen, headRec.Right, headRec.Top, headRec.Right, headRec.Bottom);
             e.Graphics.DrawString(item.Content, this.ColumnHeadersDefaultCellStyle.Font, Brushes.Black,headRec, foramt);
         }

填充矩形時，記得要給矩形的常和寬減去一個像素，這樣才不會與相鄰的矩形重疊區域導致矩形的邊線顯示不出來。還有這里的要設置 ColumnHeadersHeightSizeMode 屬性，如果不把它設成 DisableResizing ，那么表頭的高度是改變不了的，這樣即使設置了二維，三維，n維，最終只是一維。

這里用到的一些輔助方法如下，分別是通過坐標計算出高度和寬度。

代碼如下:
private int ComputeWidth(int startX, int endX)
         {
             int width = 0;
             for (int i = startX; i <= endX; i++)
                 width+= this.Columns[i].Width;
             return width;
         }

         private int ComputeHeight(int startY, int endY)
         {
             return _baseColumnHeadHeight * (endY - startY+1);
         }

給一段使用的實例代碼，這里要預先給DataGridView每一列設好綁定的字段，否則自動添加的列是做不出效果來的。

代碼如下:
HeaderItem item= this.boundGridView1.Headers.GetHeaderByLocation(0, 0);
             item.EndY = 2;
             item = this.boundGridView1.Headers.GetHeaderByLocation(9,0 );
             item.EndY = 2;
             item = this.boundGridView1.Headers.GetHeaderByLocation(10, 0);
             item.EndY = 2;
             item = this.boundGridView1.Headers.GetHeaderByLocation(11, 0);
             item.EndY = 2;

             this.boundGridView1.Headers.AddHeader(1, 2, 1, 1, "語文");
             this.boundGridView1.Headers.AddHeader(3, 4, 1, 1, "數學");
             this.boundGridView1.Headers.AddHeader(5, 6, 1, 1, "英語");
             this.boundGridView1.Headers.AddHeader(7, 8, 1, 1, "X科");
             this.boundGridView1.Headers.AddHeader(1, 8, 2, 2, "成績");

效果圖如下所示

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控件的完整代碼
代碼如下:

     public class BoundGridView : DataGridView
     {
         private int _baseColumnHeadHeight;

         public BoundGridView():base()
         {
             this.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.DisableResizing;
             _baseColumnHeadHeight = this.ColumnHeadersHeight;
             this.Headers = new HeaderCollection(this.Columns);
         }

         public HeaderCollection Headers{ get;private set; }

         protected override void OnCellPainting(DataGridViewCellPaintingEventArgs e)
         {
             if (e.ColumnIndex == -1 || e.RowIndex != -1)
             {
                 base.OnCellPainting(e);
                 return;
             }
             int lev=this.Headers.GetHeaderLevels();
             this.ColumnHeadersHeight = (lev + 1) * _baseColumnHeadHeight;
             for (int i = 0; i <= lev; i++)
             {
                 HeaderItem tempHeader= this.Headers.GetHeaderByLocation(e.ColumnIndex, i);
                 if (tempHeader==null|| i != tempHeader.EndY || e.ColumnIndex != tempHeader.StartX) continue;
                 DrawHeader(tempHeader, e);
             }
             e.Handled = true;
         }

         private int ComputeWidth(int startX, int endX)
         {
             int width = 0;
             for (int i = startX; i <= endX; i++)
                 width+= this.Columns[i].Width;
             return width;
         }

         private int ComputeHeight(int startY, int endY)
         {
             return _baseColumnHeadHeight * (endY - startY+1);
         }

         private void DrawHeader(HeaderItem item,DataGridViewCellPaintingEventArgs e)
         {
             if (this.ColumnHeadersHeightSizeMode != DataGridViewColumnHeadersHeightSizeMode.DisableResizing)
                 this.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.DisableResizing;
             int lev=this.Headers.GetHeaderLevels();
             lev=(lev-item.EndY)*_baseColumnHeadHeight;

             SolidBrush backgroundBrush = new SolidBrush(e.CellStyle.BackColor);
             SolidBrush lineBrush = new SolidBrush(this.GridColor);
             Pen linePen = new Pen(lineBrush);
             StringFormat foramt = new StringFormat();
             foramt.Alignment = StringAlignment.Center;
             foramt.LineAlignment = StringAlignment.Center;

             Rectangle headRec = new Rectangle(e.CellBounds.Left, lev, ComputeWidth(item.StartX, item.EndX)-1, ComputeHeight(item.StartY, item.EndY)-1);
             e.Graphics.FillRectangle(backgroundBrush, headRec);
             e.Graphics.DrawLine(linePen, headRec.Left, headRec.Bottom, headRec.Right, headRec.Bottom);
             e.Graphics.DrawLine(linePen, headRec.Right, headRec.Top, headRec.Right, headRec.Bottom);
             e.Graphics.DrawString(item.Content, this.ColumnHeadersDefaultCellStyle.Font, Brushes.Black,headRec, foramt);
         }
     }

     public class HeaderItem
     {
         private int _startX;
         private int _startY;
         private int _endX;
         private int _endY;
         private bool _baseHeader;

         public HeaderItem(int startX, int endX, int startY, int endY, string content)
         {
             this._endX = endX;
             this._endY = endY;
             this._startX = startX;
             this._startY = startY;
             this.Content = content;
         }

         public HeaderItem(int x, int y, string content):this(x,x,y,y,content)
         {

         }

         public HeaderItem()
         {

         }

         public static HeaderItem CreateBaseHeader(int x,int y,string content)
         {
             HeaderItem header = new HeaderItem();
             header._endX= header._startX = x;
             header._endY= header._startY = y;
             header._baseHeader = true;
             header.Content = content;
             return header;
         }

         public int StartX
         {
             get { return _startX; }
             set
             {
                 if (value > _endX)
                 {
                     _startX = _endX;
                     return;
                 }
                 if (value < 0) _startX = 0;
                 else _startX = value;
             }
         }

         public int StartY
         {
             get { return _startY; }
             set
             {
                 if (_baseHeader)
                 {
                     _startY = 0;
                     return;
                 }
                 if (value > _endY)
                 {
                     _startY = _endY;
                     return;
                 }
                 if (value < 0) _startY = 0;
                 else _startY = value;
             }
         }

         public int EndX
         {
             get { return _endX; }
             set
             {
                 if (_baseHeader)
                 {
                     _endX = _startX;
                     return;
                 }
                 if (value < _startX)
                 {
                     _endX = _startX;
                     return;
                 }
                 _endX = value;
             }
         }

         public int EndY
         {
             get { return _endY; }
             set
             {
                 if (value < _startY)
                 {
                     _endY = _startY;
                     return;
                 }
                 _endY = value;
             }
         }

         public bool IsBaseHeader
         {get{ return _baseHeader;} }

         public string Content { get; set; }
     }

     public class HeaderCollection
     {
         private List<HeaderItem> _headerList;
         private bool _iniLock;

         public DataGridViewColumnCollection BindCollection{get;set;}

         public HeaderCollection(DataGridViewColumnCollection cols)
         {
             _headerList = new List<HeaderItem>();
             BindCollection=cols;
             _iniLock = false;
         }

         public int GetHeaderLevels()
         {
             int max = 0;
             foreach (HeaderItem item in _headerList)
                 if (item.EndY > max)
                     max = item.EndY;

             return max;
         }

         public List<HeaderItem> GetBaseHeaders()
         {
             List<HeaderItem> list = new List<HeaderItem>();
             foreach (HeaderItem item in _headerList)
                 if (item.IsBaseHeader) list.Add(item);
             return list;
         }

         public HeaderItem GetHeaderByLocation(int x, int y)
         {
             if (!_iniLock) InitHeader();
             HeaderItem result=null;
             List<HeaderItem> temp = new List<HeaderItem>();
             foreach (HeaderItem item in _headerList)
                 if (item.StartX <= x && item.EndX >= x)
                     temp.Add(item);
             foreach (HeaderItem item in temp)
                 if (item.StartY <= y && item.EndY >= y)
                     result = item;

             return result;
         }

         public IEnumerator GetHeaderEnumer()
         {
             return _headerList.GetEnumerator();
         }

         public void AddHeader(HeaderItem header)
         {
             this._headerList.Add(header);
         }

         public void AddHeader(int startX, int endX, int startY, int endY, string content)
         {
             this._headerList.Add(new HeaderItem(startX,endX,startY,endY,content));
         }

         public void AddHeader(int x, int y, string content)
         {
             this._headerList.Add(new HeaderItem(x, y, content));
         }

         public void RemoveHeader(HeaderItem header)
         {
             this._headerList.Remove(header);
         }

         public void RemoveHeader(int x, int y)
         {
            HeaderItem header= GetHeaderByLocation(x, y);
            if (header != null) RemoveHeader(header);
         }

         private void InitHeader()
         {
             _iniLock = true;
             for (int i = 0; i < this.BindCollection.Count; i++)
                 if(this.GetHeaderByLocation(i,0)==null)
                 this._headerList.Add(HeaderItem.CreateBaseHeader(i,0 , this.BindCollection[i].HeaderText));
             _iniLock = false;
         }
     }

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