Question

我试图用组合框来改变字体大小。问题是@runtime我得到一个没有价值的错误。在表单加载上我将selectedindexitem设置为3

mycode的：

更新：仅当我使用数字设置整数值时才有效...我希望能够使用comboboox1更改它。

  Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ComboBox1.SelectedIndex = 2
    End Sub

     Dim myFontSize As Integer = 120
    Dim myFont As New Font("Arial", myFontSize, FontStyle.Bold Or FontStyle.Italic)
    Dim Loc As Point
    Dim Pxy As Point

    Private Sub PictureBox1_MouseMove(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseMove
        txtButton.Text = MouseButtons.Left
        If e.Button = MouseButtons.Left Then
            Loc = e.Location
            Me.PictureBox1.Invalidate()
        End If
    End Sub

    Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint


        Dim pt As Point = PictureBox1.PointToClient(Control.MousePosition)
        e.Graphics.DrawString(txtA.Text, myFont, Brushes.Black, pt.X, pt.Y)
    End Sub
Private Sub ComboBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles ComboBox1.KeyPress
        Dim KeyAscii As Integer = Asc(e.KeyChar)
        Select Case KeyAscii
            Case 8, 27, 48 To 57, 9
            Case Else
                KeyAscii = 0
        End Select
        If KeyAscii = 0 Then
            e.Handled = True
        Else
            e.Handled = False
        End If
    End Sub

也许并不重要，但我在Combobox_KeyPress上只有代码才能允许数字。任何帮助或指向，我是正确的直线吗？

Answer 1

如果我理解得很好，问题是在表单加载事件中它会引发异常，因为组合框中没有选定的项目吗？

此外，您在哪里尝试运行该代码？。

无论如何，你可以编写一个条件来确保有一个选定的项目，然后避免该异常：

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) _
Handles ComboBox1.SelectedIndexChanged

    Dim cb As ComboBox = DirectCast(sender, ComboBox)

    If cb.SelectedItem IsNot Nothing Then

        Using font As New Font("Arial", Convert.ToInt32(cb.Text),
                               FontStyle.Bold Or 
                               FontStyle.Italic)

            otherControl.Font = font

        End Using

    End If

End Sub

Answer 2

我得到了工作！

Dim myFontSize As Integer
        Integer.TryParse(ComboBox1.Text, myFontSize)
        Dim myFont As New Font("Arial", myFontSize, FontStyle.Bold Or FontStyle.Italic)

这就是诀窍。

Answer 3

您应该从FontSize获取ComboBox.SelectedItem而不是来自父级。此外，“FontSize”已经是字符串中的变量，因此您应该将自定义变量命名为其他内容：

Dim MyFontSize As Integer = CInt(myComboBox.SelectedItem)
Dim myFont As New Font("Arial", MyFontSize, FontStyle.Bold Or FontStyle.Italic)

组合框到整数值@运行时更改FontSize

3 个答案: