在RichTextBox中设置首行缩进

 

   Private position(1024) As Integer '用来记录每段首行位置的数组

   Private currentposition As Integer = 0

Private rtb_Selectionlen As Integer = 0

Private rtb As RichTextBox

    '首行缩进

    Public Sub SetFirstLineIndent()

 

        '获取当前插入点的位置

        currentposition = rtb.GetFirstCharIndexOfCurrentLine

        rtb_Selectionlen = rtb.SelectionLength

        '找出全部换行符的位置并存入数组中

        Call FindFirstCharOfParagraph()

        '找到插入点所在段落的首字符位置

        FindPositonofFirstChar()

        '进行首行缩进

        InsertIndent(firstlineindentvalue)

    End Sub

 

    '找出全部段落首行首字符的位置并存入数组中

    Public Sub FindFirstCharOfParagraph()

        Dim indexofposition As Integer = 0

        Dim startposition As Integer = 0

        Dim indexofarray As Integer = 1 '数组的索引从1开始，因为0已经被缺省

        position(0) = 0 '将第一段定为0

        Do

            indexofposition = rtb.Find(Chr(13), startposition, RichTextBoxFinds.None)

            If indexofposition >= 0 Then

                position(indexofarray) = indexofposition + 1 '当前换行符的位置加1就等于下一段的首字符位置

                startposition = indexofposition + 1

                indexofarray += 1

            Else

                'MsgBox("未找到!")

            End If

        Loop While indexofposition >= 0

    End Sub

 

    '获取当前字符所在行的首字符位置

    Public Function FindPositionOfCurrentLine() As Integer

 

        currentposition = rtb.GetFirstCharIndexOfCurrentLine

        rtb_Selectionlen = rtb.SelectionLength

        Return currentposition

    End Function

 

    '找到插入点所在段落的首字符位置

    Public Function FindPositonofFirstChar() As Integer

        '方法是：首先找到当前插入点所在段落的换行符的位置,然后加1与数组position进行匹配

        '如果匹配则返回当前数组元素的前一个元素的值

        Try

            Dim indexofposition As Integer = 0

            Dim i_index As Integer = 0

            For Each i As Integer In position

                If currentposition >= position(i_index) And currentposition < position(i_index + 1) Then

                    Return position(i_index)

                ElseIf currentposition = position(i_index + 1) Then

                    Return position(i_index + 1)

                Else

                    i_index += 1

                End If

            Next

        Catch ex As Exception

            MsgBox(ex.Message)

            Exit Function

        End Try

    End Function

 

    '向剪贴板中写入缩进字符并粘贴到插入点

    Public Function InsertIndent(ByVal indentvalue As Integer) As Integer

        Try

            Dim indentstr As String = ""

            For i As Integer = 1 To indentvalue * 8

                indentstr &= Chr(32)

            Next

            rtb.SelectionStart = FindPositonofFirstChar()

            rtb.SelectionLength = 0

            Clipboard.Clear()

            Clipboard.SetText(indentstr, TextDataFormat.Text)

            rtb.Paste(DataFormats.GetFormat(DataFormats.Text))

        Catch ex As Exception

            MsgBox(ex.Message)

            Exit Function

        End Try

    End Function