Vb.net NET计算器；操作后清除文本框

我正在做一个简单的计算器，它正在工作，但我面临的问题是，一旦操作完成，清除文本框，我想开始另一个。 假设我做了一个求和，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，我想知道我怎么做

由于我是初学者，请保持你的答案简单

这是我目前拥有的代码：

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

---

尝试使用类型为boolean的simpel全局变量，该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，您应该使用新的sub向查看器添加文本，以使代码更清晰并避免重复：

...
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，以避免再次清除字段。 在按钮中。单击事件处理程序，您只需使用此子项，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，将ClearField变量设置为true，以便下次添加数字时程序重新启动：

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

---

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。如果已设置：

清除文本框。 将标志设置回0。 在结果事件中，单击“在查看器后添加此行”。Text=result

下面是一个按钮示例：

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

---

对每个按钮都执行此操作。

使用全局变量来识别键入的是数字和操作序列，还是在结果按钮之后的序列的开始

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)

---

伙计们，要尽快检查他们！非常感谢您的帮助：不需要声明标志吗？我试过了，但即使没有抛出任何错误，它也不起作用……当然需要声明标志。在Dim操作后将其全局声明为字符串作为Dim标志作为整数

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)