如何防止在Visual中发生第二个textchanged事件
如何防止在Visual中发生第二个textchanged事件
提问于 2013-11-12 16:20:00
我正在Visual 2012中编写一个Visual程序，我遇到了一个我无法自己解决的问题。我使用两个文本框和两个组合框。应用程序中没有按钮。在输入数字时，我使用textchanged事件触发计算。它将使用一个文本框工作，但当它在另一个文本框中显示答案时，它将触发文本框textchanged事件。因此，没有给我正确的答案。顺便说一下，这是一个单位转换器，转换长度，如米到毫米，米到脚，米到英寸，等等。
Public Class frmMain
' class-scope variables
Dim decUnit1 As Decimal
Dim decUnit2 As Decimal
Dim intFlag As Integer
Private Sub frmMain_Load(sender As Object, e As EventArgs) Handles Me.Load
PopCombo()
cboUnitType.SelectedIndex = 0
End Sub
Private Sub PopCombo()
' populates the comboBoxes and sets default selection
' populate the comboBox accordingly
If cboUnitType.SelectedIndex = 0 Then
ClearBox()
With Me.cbo1.Items
.Add("Meter")
.Add("Milimeter")
.Add("Foot")
.Add("Inch")
End With
With Me.cbo2.Items
.Add("Meter")
.Add("Milimeter")
.Add("Foot")
.Add("Inch")
End With
' set default ComboBox index selection
cbo1.SelectedIndex = 1
cbo2.SelectedIndex = 3
ElseIf cboUnitType.SelectedIndex = 1 Then
ClearBox()
With Me.cbo1.Items
.Add("Celsius")
.Add("Fahrenheit")
End With
With Me.cbo2.Items
.Add("Celsius")
.Add("Fahrenheit")
End With
cbo1.SelectedIndex = 0
cbo2.SelectedIndex = 1
End If
End Sub
Private Sub ClearBox()
' clears the comboBox
cbo1.Items.Clear()
cbo2.Items.Clear()
End Sub
Private Sub cboUnitType_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cboUnitType.SelectedIndexChanged
PopCombo()
End Sub
Private Sub txtUnit1_TextChanged(sender As Object, e As EventArgs) Handles txtUnit1.TextChanged
Decimal.TryParse(txtUnit1.Text, decUnit1)
Decimal.TryParse(txtUnit2.Text, decUnit2)
If cboUnitType.SelectedIndex = 0 Then
' converts meter to...
If cbo1.SelectedIndex = 0 AndAlso cbo2.SelectedIndex = 0 Then
' meter
txtUnit2.Text = txtUnit1.Text
ElseIf cbo1.SelectedIndex = 0 AndAlso cbo2.SelectedIndex = 1 Then
' millimeter
txtUnit2.Text = (decUnit1 * 1000).ToString
ElseIf cbo1.SelectedIndex = 0 AndAlso cbo2.SelectedIndex = 2 Then
' foot
txtUnit2.Text = (decUnit1 * 3.28084).ToString
ElseIf cbo1.SelectedIndex = 0 AndAlso cbo2.SelectedIndex = 3 Then
' inch
txtUnit2.Text = (decUnit1 * 39.3701).ToString
End If
' converts millimeter to...
If cbo1.SelectedIndex = 1 AndAlso cbo2.SelectedIndex = 0 Then
' meter
txtUnit2.Text = (decUnit1 * 0.001).ToString
ElseIf cbo1.SelectedIndex = 1 AndAlso cbo2.SelectedIndex = 1 Then
' millimeter
txtUnit2.Text = txtUnit1.Text
ElseIf cbo1.SelectedIndex = 1 AndAlso cbo2.SelectedIndex = 2 Then
' foot
txtUnit2.Text = (decUnit1 * 0.00328084).ToString
ElseIf cbo1.SelectedIndex = 1 AndAlso cbo2.SelectedIndex = 3 Then
' inch
txtUnit2.Text = (decUnit1 * 0.0393701).ToString
End If
' converts foot to...
If cbo1.SelectedIndex = 2 AndAlso cbo2.SelectedIndex = 0 Then
' meter
txtUnit2.Text = (decUnit1 * 0.3048).ToString
ElseIf cbo1.SelectedIndex = 2 AndAlso cbo2.SelectedIndex = 1 Then
' millimeter
txtUnit2.Text = (decUnit1 * 304.8).ToString
ElseIf cbo1.SelectedIndex = 2 AndAlso cbo2.SelectedIndex = 2 Then
' foot
txtUnit2.Text = txtUnit1.Text
ElseIf cbo1.SelectedIndex = 2 AndAlso cbo2.SelectedIndex = 3 Then
' inch
txtUnit2.Text = (decUnit1 * 12).ToString
End If
' converts inch to...
If cbo1.SelectedIndex = 3 AndAlso cbo2.SelectedIndex = 0 Then
' meter
txtUnit2.Text = (decUnit1 * 0.0254).ToString
ElseIf cbo1.SelectedIndex = 3 AndAlso cbo2.SelectedIndex = 1 Then
' millimeter
txtUnit2.Text = (decUnit1 * 25.4).ToString
ElseIf cbo1.SelectedIndex = 3 AndAlso cbo2.SelectedIndex = 2 Then
' foot
txtUnit2.Text = (decUnit1 * 0.0833333).ToString
ElseIf cbo1.SelectedIndex = 3 AndAlso cbo2.SelectedIndex = 3 Then
' inch
txtUnit2.Text = txtUnit1.Text
End If
End If
End Sub
Private Sub txtUnit2_TextChanged(sender As Object, e As EventArgs) Handles txtUnit2.TextChanged
Decimal.TryParse(txtUnit1.Text, decUnit1)
Decimal.TryParse(txtUnit2.Text, decUnit2)
If cboUnitType.SelectedIndex = 0 Then
' converts meter to...
If cbo1.SelectedIndex = 0 AndAlso cbo2.SelectedIndex = 0 Then
' meter
txtUnit1.Text = txtUnit2.Text
ElseIf cbo1.SelectedIndex = 1 AndAlso cbo2.SelectedIndex = 0 Then
' millimeter
txtUnit1.Text = (decUnit2 * 1000).ToString
ElseIf cbo1.SelectedIndex = 2 AndAlso cbo2.SelectedIndex = 0 Then
' foot
txtUnit1.Text = (decUnit2 * 3.28084).ToString
ElseIf cbo1.SelectedIndex = 3 AndAlso cbo2.SelectedIndex = 0 Then
' inch
txtUnit1.Text = (decUnit2 * 39.3701).ToString
End If
' converts millimeter to...
If cbo1.SelectedIndex = 0 AndAlso cbo2.SelectedIndex = 1 Then
' meter
txtUnit1.Text = (decUnit2 * 0.001).ToString
ElseIf cbo1.SelectedIndex = 1 AndAlso cbo2.SelectedIndex = 1 Then
' millimeter
txtUnit1.Text = txtUnit2.Text
ElseIf cbo1.SelectedIndex = 2 AndAlso cbo2.SelectedIndex = 1 Then
' foot
txtUnit1.Text = (decUnit2 * 0.00328084).ToString
ElseIf cbo1.SelectedIndex = 3 AndAlso cbo2.SelectedIndex = 1 Then
' inch
txtUnit1.Text = (decUnit2 * 0.0393701).ToString
End If
' converts foot to...
If cbo1.SelectedIndex = 0 AndAlso cbo2.SelectedIndex = 2 Then
' meter
txtUnit1.Text = (decUnit2 * 0.3048).ToString
ElseIf cbo1.SelectedIndex = 1 AndAlso cbo2.SelectedIndex = 2 Then
' millimeter
txtUnit1.Text = (decUnit2 * 304.8).ToString
ElseIf cbo1.SelectedIndex = 2 AndAlso cbo2.SelectedIndex = 2 Then
' foot
txtUnit1.Text = txtUnit2.Text
ElseIf cbo1.SelectedIndex = 3 AndAlso cbo2.SelectedIndex = 2 Then
' inch
txtUnit1.Text = (decUnit2 * 12).ToString
End If
' converts inch to...
If cbo1.SelectedIndex = 0 AndAlso cbo2.SelectedIndex = 3 Then
' meter
txtUnit1.Text = (decUnit2 * 0.0254).ToString
ElseIf cbo1.SelectedIndex = 1 AndAlso cbo2.SelectedIndex = 3 Then
' millimeter
txtUnit1.Text = (decUnit2 * 25.4).ToString
ElseIf cbo1.SelectedIndex = 2 AndAlso cbo2.SelectedIndex = 3 Then
' foot
txtUnit1.Text = (decUnit2 * 0.0833333).ToString
ElseIf cbo1.SelectedIndex = 3 AndAlso cbo2.SelectedIndex = 3 Then
' inch
txtUnit1.Text = txtUnit1.Text
End If
End If
End Sub
End Class回答 1
Stack Overflow用户
回答已采纳
发布于 2013-11-13 17:08:15
在更新文本框的text属性时，需要使用一两个布尔变量来抑制文本更改事件。下面是一个将F级转换为C和back的示例，并允许您在两个文本框中键入一个值：
Public Class Form4
Dim suppressTextBox1TextChanged As Boolean = False
Dim suppressTextBox2TextChanged As Boolean = False
Private Sub txtDegreesF_TextChanged(sender As System.Object, e As System.EventArgs) Handles txtDegreesF.TextChanged
'Convert to Celsius
'Only do the calculation if we are typing the textbox
If Not suppressTextBox1TextChanged Then
Dim degreesF As Double
Dim degreesC As Double
If Double.TryParse(txtDegreesF.Text, degreesF) Then
degreesC = (degreesF - 32) * (5 / 9)
suppressTextBox2TextChanged = True
txtDegreesC.Text = degreesC.ToString()
suppressTextBox2TextChanged = False
End If
End If
End Sub
Private Sub txtDegreesC_TextChanged(sender As System.Object, e As System.EventArgs) Handles txtDegreesC.TextChanged
'Convert to Fahrenheit
'Only do the calculation if we are typing the textbox
If Not suppressTextBox2TextChanged Then
Dim degreesF As Double
Dim degreesC As Double
If Double.TryParse(txtDegreesC.Text, degreesC) Then
degreesF = (degreesC * 1.8) + 32
suppressTextBox1TextChanged = True
txtDegreesF.Text = degreesF.ToString()
suppressTextBox1TextChanged = False
End If
End If
End Sub
End Class页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/19934377
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