在RichTextBox中为vb.net中的多种字体设置选择字体大小

Question

我想使用组合框更改RichTextBox 中的字体大小。如果我们使用此代码在选择文本中使用一种字体，则很容易更改字体大小。

RichTextBox1.SelectionFont = New Font(SelectionFont.FontFamily, CInt(ToolStripComboBox3.Text), RichTextBox1.SelectionFont.Style)

但如果我们在选择中有多种字体，它就不起作用了。

我有另一个选择的代码来解决这个问题。 But the only problem with this code is that it is good for less then 2000 characters - but when the selection text is large it is worthless.请看下面的代码：

 Public rtbTemp As New RichTextBox()
    Public Sub ChangeFontSize(ByVal rtb As RichTextBox, ByVal fontSize As Single)
        'This method should handle cases that occur when multiple fonts/styles are selected
        ' Parameters:-
        ' fontSize - the fontsize to be applied, eg 33.5
        If fontSize <= 0.0 Then
            Throw New System.InvalidProgramException("Invalid font size parameter to ChangeFontSize")
        End If
        Dim rtb1start As Integer = rtb.SelectionStart
        Dim len As Integer = rtb.SelectionLength
        Dim rtbTempStart As Integer = 0
        ' If len <= 1 and there is a selection font, amend and return
        If len <= 1 AndAlso rtb.SelectionFont IsNot Nothing Then
            rtb.SelectionFont = New Font(rtb.SelectionFont.FontFamily, fontSize, rtb.SelectionFont.Style)
            Return
        End If
        ' Step through the selected text one char at a time
        rtbTemp.Rtf = rtb.SelectedRtf
        For i As Integer = 0 To len - 1
            rtbTemp.[Select](rtbTempStart + i, 1)
            rtbTemp.SelectionFont = New Font(rtbTemp.SelectionFont.FontFamily, fontSize, rtbTemp.SelectionFont.Style)
        Next

        ' Replace & reselect
        rtbTemp.[Select](rtbTempStart, len)
        rtb.SelectedRtf = rtbTemp.SelectedRtf
        rtb.[Select](rtb1start, len)
        Return
    End Sub

Answer 1

代码如下： 字体大小组合框的 Xaml：

            <ComboBox Width="50" Name="FontsSizeCombo" FontSize="12" ItemsSource="{Binding}">
                <ComboBoxItem Content="8"/>
                <ComboBoxItem Content="9" />
                <ComboBoxItem Content="10" />
                <ComboBoxItem Content="11" />
                <ComboBoxItem Content="12" />
                <ComboBoxItem Content="14" />
                <ComboBoxItem Content="16" />
                <ComboBoxItem Content="18" />
                <ComboBoxItem Content="22" />
                <ComboBoxItem Content="24" />
                <ComboBoxItem Content="26" />
                <ComboBoxItem Content="36" />
                <ComboBoxItem Content="48" />
                <ComboBoxItem Content="72" />
            </ComboBox>

工作 Vb.Net 代码：

Private Sub FontsSizeCombo_DropDownClosed(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles FontsSizeCombo.DropDownClosed
    mainRTB.Selection.ApplyPropertyValue(RichTextBox.FontSizeProperty, FontsSizeCombo.Text)
End Sub

mainRtb 是我的富文本框。如果它是正确的，请检查这个作为答案。谢谢。

Answer 2

---

这里我改变了一些东西

Public rtbTemp As New RichTextBox()

Public Sub ChangeFontSize(ByVal rtb As RichTextBox, ByVal fontSize As Single, ByVal fntName As String)

    If fontSize <= 0.0 Then
        Throw New System.InvalidProgramException("Invalid font size parameter to ChangeFontSize")
    End If
    Dim rtb1start As Double = rtb.SelectionStart
    Dim len As Double = rtb.SelectionLength
    Dim rtbTempStart As Double = 0
    ' If len <= 1 and there is a selection font, amend and return
    If len <= 1 AndAlso rtb.SelectionFont IsNot Nothing Then
        rtb.SelectionFont = New Font(fntName, fontSize, rtb.SelectionFont.Style)
        Return
    End If
    ' Step through the selected text one char at a time
    rtbTemp.Rtf = rtb.SelectedRtf
    For i As Double = 0 To len - 1
        rtbTemp.[Select](rtbTempStart + i, 1)
        rtbTemp.SelectionFont = New Font(fntName, fontSize, rtbTemp.SelectionFont.Style)
    Next

    ' Replace & reselect
    rtbTemp.[Select](rtbTempStart, len)
    rtb.SelectedRtf = rtbTemp.SelectedRtf
    rtb.[Select](rtb1start, len)
    Return

End Sub