Henry手記：WinForm Datagrid結構剖析（三）類程式碼
-------------------X類的程式碼X---------------------<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
Option Strict On
Option Explicit On
Imports System.Collections
Imports System.ComponentModel
Imports System.Drawing
Imports System.Windows.Forms
Imports System.Data
Public
‘與DataGridTextBox類相類似地定義一個在下拉框列類中使用的ComboBox
Inherits ComboBox
Public Sub New()
MyBase.New()
End Sub
Public isInEditOrNavigateMode As Boolean = True
End Class
Public Class DataGridComboBoxColumn
Inherits DataGridColumnStyle
' 與使用者介面相關的變數
Private xMargin As Integer = 2
Private
Private Combo As DataGridComboBox
Private _DisplayMember As String
Private _ValueMember As String
' 用於跟蹤編輯狀態變化的變數
Private OldVal As String = String.Empty
Private InEdit As Boolean = False
'建構函式 – 例項的DisplayMember, ValueMember值為由父類傳來的integer型別的值
Public Sub New(ByRef DataSource As
ByVal DisplayMember As Integer, _
ByVal ValueMember As Integer)
Combo = New DataGridComboBox()
_DisplayMember = DataSource.Columns.Item(index:=DisplayMember).ToString
_ValueMember = DataSource.Columns.Item(index:=ValueMember).ToString
With Combo
.Visible = False
.DataSource = DataSource
.DisplayMember = _DisplayMember
.ValueMember = _ValueMember
End With
End Sub
'建構函式– 例項的DisplayMember, ValueMember 是String型別的值
Public Sub New(ByRef DataSource As DataTable, _
ByVal DisplayMember As String, _
ByVal ValueMember As String)
Combo = New DataGridComboBox()
With Combo
.Visible = False
.DataSource = DataSource
.DisplayMember = DisplayMember
.ValueMember = ValueMember
End With
End Sub
'------------------------------------------------------
'從 DataGridColumnStyle類繼承下來的方法
'------------------------------------------------------
' 焦點離開combobox格後的改變
Protected Overloads Overrides Sub Abort(ByVal RowNum As Integer)
Debug.WriteLine("Abort()")
RollBack()
HideComboBox()
EndEdit()
End Sub
' 接受改變
Protected Overloads Overrides Function Commit(ByVal DataSource As CurrencyManager, _
ByVal RowNum As Integer) As Boolean
HideComboBox()
If Not InEdit Then
Return True
End If
Try
Dim Value As Object = Combo.SelectedValue
If NullText.Equals(Value) Then
Value = Convert.DBNull
End If
SetColumnValueAtRow(DataSource, RowNum, Value)
Catch e As Exception
RollBack()
Return False
End Try
EndEdit()
Return True
End Function
' 移開聚焦
Protected Overloads Overrides Sub ConcedeFocus()
Combo.Visible = False
End Sub
' 編輯單元格
Protected Overloads Overrides Sub Edit(ByVal Source As CurrencyManager, _
ByVal Rownum As Integer, _
ByVal Bounds As Rectangle, _
ByVal [ReadOnly] As Boolean, _
ByVal InstantText As String, _
ByVal CellIsVisible As Boolean)
Combo.Text = String.Empty
Dim OriginalBounds As Rectangle = Bounds
OldVal = Combo.Text
If CellIsVisible Then
Bounds.Offset(xMargin, yMargin)
Bounds.Width -= xMargin * 2
Bounds.Height -= yMargin
Combo.Bounds = Bounds
Combo.Visible = True
Else
Combo.Bounds = OriginalBounds
Combo.Visible = False
End If
Combo.SelectedValue = GetText(GetColumnValueAtRow(Source, Rownum))
If Not InstantText Is Nothing Then
Combo.SelectedValue = InstantText
End If
Combo.RightToLeft = Me.DataGridTableStyle.DataGrid.RightToLeft
Combo.Focus()
If InstantText Is Nothing Then
Combo.SelectAll()
Else
Dim [End] As Integer = Combo.Text.Length
Combo.Select([End], 0)
End If
If Combo.Visible Then
DataGridTableStyle.DataGrid.Invalidate(OriginalBounds)
End If
InEdit = True
End Sub
Protected Overloads Overrides Function GetMinimumHeight() As Integer
' 設定combobox的最小高度
Return Combo.PreferredHeight + yMargin
End Function
Protected Overloads Overrides Function GetPreferredHeight(ByVal g As Graphics, _
ByVal Value As Object) As Integer
Debug.WriteLine("GetPreferredHeight()")
Dim NewLineIndex As Integer = 0
Dim NewLines As Integer = 0
Dim ValueString As String = Me.GetText(Value)
Do
While NewLineIndex <> -1
NewLineIndex = ValueString.IndexOf("r/n", NewLineIndex + 1)
NewLines += 1
End While
Loop
Return FontHeight * NewLines + yMargin
End Function
Protected Overloads Overrides Function GetPreferredSize(ByVal g As Graphics, _
ByVal Value As Object) As Size
Dim Extents As Size = Size.Ceiling(g.MeasureString(GetText(Value), _
Me.DataGridTableStyle.DataGrid.Font))
Extents.Width += xMargin * 2 + DataGridTableGridLineWidth
Extents.Height += yMargin
Return Extents
End Function
Protected Overloads Overrides Sub Paint(ByVal g As Graphics, _
ByVal Bounds As Rectangle, _
ByVal Source As CurrencyManager, _
ByVal RowNum As Integer)
Paint(g, Bounds, Source, RowNum, False)
End Sub
Protected Overloads Overrides Sub Paint(ByVal g As Graphics, _
ByVal Bounds As Rectangle, _
ByVal Source As CurrencyManager, _
ByVal RowNum As Integer, _
ByVal AlignToRight As Boolean)
Dim Text As String = GetText(GetColumnValueAtRow(Source, RowNum))
PaintText(g, Bounds, Text, AlignToRight)
End Sub
Protected Overloads Sub Paint(ByVal g As Graphics, _
ByVal Bounds As Rectangle, _
ByVal Source As CurrencyManager, _
ByVal RowNum As Integer, _
ByVal BackBrush As Brush, _
ByVal ForeBrush As Brush, _
ByVal AlignToRight As Boolean)
Dim Text As String = GetText(GetColumnValueAtRow(Source, RowNum))
PaintText(g, Bounds, Text, BackBrush, ForeBrush, AlignToRight)
End Sub
Protected Overloads Overrides Sub SetDataGridInColumn(ByVal Value As DataGrid)
MyBase.SetDataGridInColumn(Value)
If Not (Combo.Parent Is Value) Then
If Not (Combo.Parent Is Nothing) Then
Combo.Parent.Controls.Remove(Combo)
End If
End If
If Not (Value Is Nothing) Then Value.Controls.Add(Combo)
End Sub
Protected Overloads Overrides Sub UpdateUI(ByVal Source As CurrencyManager, _
Val RowNum As Integer, ByVal InstantText As String)
Combo.Text = GetText(GetColumnValueAtRow(Source, RowNum))
If Not (InstantText Is Nothing) Then
Combo.Text = InstantText
End If
End Sub
－－－未完，見（三）使用程式碼一文－－－－－－－－－
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