Question

我正在使用一个简单的计算器并且它正在工作，但是一旦操作完成我就会面临清除文本框的问题而我想开始另一个。让我们说我做了一笔钱，结果是6，当我点击一个数字开始另一个操作时，它没有清除文本框，我想知道我该怎么办？

因为我是初学者，请保持简单的答案。

这是我目前的代码：

Public Class Form1
Dim FirstNumber As Long
Dim Operation As String


'BUTTONS
'Numbers

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Viewer.Text = Viewer.Text + "1"
End Sub

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
    Viewer.Text = Viewer.Text + "2"
End Sub

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
    Viewer.Text = Viewer.Text + "3"
End Sub

Private Sub Button4_Click(sender As Object, e As EventArgs) Handles Button4.Click
    Viewer.Text = Viewer.Text + "4"
End Sub

Private Sub Button5_Click(sender As Object, e As EventArgs) Handles Button5.Click
    Viewer.Text = Viewer.Text + "5"
End Sub

Private Sub Button6_Click(sender As Object, e As EventArgs) Handles Button6.Click
    Viewer.Text = Viewer.Text + "6"
End Sub

Private Sub Button7_Click(sender As Object, e As EventArgs) Handles Button7.Click
    Viewer.Text = Viewer.Text + "7"
End Sub

Private Sub Button8_Click(sender As Object, e As EventArgs) Handles Button8.Click
    Viewer.Text = Viewer.Text + "8"
End Sub

Private Sub Button9_Click(sender As Object, e As EventArgs) Handles Button9.Click
    Viewer.Text = Viewer.Text + "9"
End Sub

Private Sub Button15_Click(sender As Object, e As EventArgs) Handles Zero.Click
    Viewer.Text = Viewer.Text + "0"
End Sub

'Buttons "," "del" "clear"

Private Sub Button14_Click(sender As Object, e As EventArgs) Handles Dot.Click
    Viewer.Text = Viewer.Text + ","
End Sub

Private Sub Button17_Click(sender As Object, e As EventArgs) Handles Del.Click
    Viewer.Text = Viewer.Text.Remove(Viewer.Text.Length - 1, 1)
End Sub

Private Sub Clear_Click(sender As Object, e As EventArgs) Handles Clear.Click
    Viewer.Text = ""
End Sub

Private Sub Sum_Click(sender As Object, e As EventArgs) Handles Sum.Click
    FirstNumber = Val(Viewer.Text)
    Operation = "SUM"
    Viewer.Text = ""
End Sub

Private Sub Minus_Click(sender As Object, e As EventArgs) Handles Minus.Click
    FirstNumber = Val(Viewer.Text)
    Operation = "MINUS"
    Viewer.Text = ""
End Sub

Private Sub Multi_Click(sender As Object, e As EventArgs) Handles Multi.Click
    FirstNumber = Val(Viewer.Text)
    Operation = "MULTI"
    Viewer.Text = ""
End Sub

Private Sub Div_Click(sender As Object, e As EventArgs) Handles Div.Click
    FirstNumber = Val(Viewer.Text)
    Operation = "DIV"
    Viewer.Text = ""
End Sub

Private Sub Result_Click(sender As Object, e As EventArgs) Handles Result.Click
    Dim SecondNumber As Long
    Dim Result As Double

    SecondNumber = Val(Viewer.Text)

    'Fx
    If Operation = "SUM" Then
        Result = FirstNumber + SecondNumber
    End If

    If Operation = "MINUS" Then
        Result = FirstNumber - SecondNumber
    End If

    If Operation = "MULTI" Then
        Result = FirstNumber * SecondNumber
    End If

    If Operation = "DIV" Then
        Result = FirstNumber / SecondNumber
    End If

    Viewer.Text = Result

End Sub

End Class

Answer 1

尝试使用boolean类型的simpel全局变量，表示要在添加数字之前清除文本，如下所示：

Public Class Form1
  Dim FirstNumber As Long
  Dim Operation As String
  Dim ClearField as Boolean = True  'At program start, you do want to start over at first
  ...

然后你应该使用一个新的子句向观众添加文字，使代码更清晰，避免重复：

...
Private Sub AddNumber(NewValue as String)
  If ClearField = True Then Viewer.Text = ""
  Viewer.Text &= NewValue
  ClearField = False
End Sub
...

清除字段一次后，将ClearField变量设置为false，以避免再次清除该字段。在Button.Click事件处理程序中，您只需使用此子而不是手动添加文本：

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    AddNumber("1")
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
    AddNumber("2")
End Sub

等等。计算结果后，您可以将ClearField变量设置为true，以便程序在下次添加数字时启动：

...
Viewer.Text = Result
ClearField = True
...

Answer 2

在代码的开头取一个标志变量。在结果单击事件上，设置标志。下次单击数字按钮时，请检查标志。如果设置：

清除文本框。
将标志设置回0。

在结果点击事件中，在Viewer.Text = Result

flag=1

以下是按钮的示例：

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
  If flag=1 then
     Viewer.Text = ""
     Viewer.Text = Viewer.Text + "1"
     flag = 0
  Else
     Viewer.Text = Viewer.Text + "1"
  End If
End Sub

为每个按钮执行此操作。

Answer 3

使用全局变量来识别键入是数字和操作的顺序，还是在结果按钮之后是否是这样的序列的开始。

Public Class Form1
Dim FirstNumber As Long
Dim Operation As String

Dim ResultPressed As Boolean

'BUTTONS
'Numbers

Private Sub Typing()
  IF ResultPressed Then ' Result button was already pressed. This number or operation typing is first button press after result button
      Viewer.Text = "";      ' so let's clear textbox
      ResultPressed = False; 
  End If
  ' If ResultPressed is false, nothing to do. Continue typing numbers ..
End

Private Sub EndTyping()
  ResultPressed = True;
End  



Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    ' Typing number or some operation fce Typing() will decides if clear textbox..
    Typing()
    Viewer.Text = Viewer.Text + "1"
End Sub

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
    ' Typing number or some operation fce Typing() will decides if clear textbox..
    Typing()
    Viewer.Text = Viewer.Text + "2"
End Sub

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
    ' Typing number or some operation fce Typing() will decides if clear textbox..
    Typing()
    Viewer.Text = Viewer.Text + "3"
End Sub


Private Sub Result_Click(sender As Object, e As EventArgs) Handles Result.Click        
    Dim SecondNumber As Long
    Dim Result As Double

    ' Numbers and operation typing finished. 
    EndTyping()

    SecondNumber = Val(Viewer.Text)

VB.NET计算器;操作后清除文本框

3 个答案: