计算器微软视觉工作室2010

Question

我已经把这段代码停止插入两个操作符，正在+，*，/但 不工作的“ - ”，当试图把（-3-3）你必须按等于按钮来允许其他运营商被插入

Public Class Form1 

    'Global variable to check if equals has been pressed 
    Dim is_equals_pressed As Boolean = False 

    Dim operator_count As Integer = 0 
    Dim allowed_input As Boolean = False 


Private Sub btnMinus_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMinus.Click 
     operator_count += 1 

     allowed_input = Check_Values() 
     If allowed_input <> False Then 

      If txtAnswer.Text = "" Then 

       If Check_Values() = False Then 
        txtAnswer.Focus() 
        Exit Sub 
       End If 
      End If 

      If is_equals_pressed = True Then 
       txtTyped.Text = txtAnswer.Text & "-" 
       txtAnswer.Text = "" 'clear the text box 
       is_equals_pressed = False 

      Else 

       txtTyped.Text += txtAnswer.Text & "-" 
       txtAnswer.Text = "" 'clear the text box 
       txtAnswer.Focus() 
      End If 
     End If 
    End Sub 


    Private Sub btnMultiply_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMultiply.Click 
     operator_count += 1 

     allowed_input = Check_Values() 
     If allowed_input <> False Then 

      If txtAnswer.Text = "" Then 

       If Check_Values() = False Then 
        txtAnswer.Focus() 
        Exit Sub 
       End If 
      End If 

      If is_equals_pressed = True Then 
       txtTyped.Text = txtAnswer.Text & "*" 
       txtAnswer.Text = "" 'clear the text box 
       is_equals_pressed = False 

      Else 

       txtTyped.Text += txtAnswer.Text & "*" 
       txtAnswer.Text = "" 'clear the text box 
       txtAnswer.Focus() 
      End If 
     End If 
    End Sub 

Private Sub btnEquals_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEquals.Click 
     Dim equation As String 


     operator_count = 0 

     'Cos, Sin, Tan 
     Dim num1 As String 
     'End 

     Dim i As Integer = 1 

     txtTyped.Text += txtAnswer.Text 
     'Capture value for Cos, Sin, Tan calculation 
     num1 = txtAnswer.Text 
     'End 

     txtAnswer.Text = ("") 'Clear the text box 

     equation = txtTyped.Text 

     'Check if equals has been pressed 
     is_equals_pressed = True 

     'Check for +, -, =,/simbol in string 
     For i = 1 To equation.Length - 1 
      If equation(i) = "+" Then 
       addNumbers(equation) 
      ElseIf equation(i) = "-" Then 
       subtrtactNumbers(equation) 
      ElseIf equation(i) = "*" Then 
       multiplyNumbers(equation) 
      ElseIf equation(i) = "/" Then 
       divideNumbers(equation) 
      ElseIf equation(i) = "^" Then 
       exponentNumber(equation) 
      ElseIf equation(i) = "%" Then 
       modulusNumbers(equation) 
      ElseIf equation.Contains("1/") Then 
       inverseNumbers(equation) 

       'We do this calculation in btnCos_Click 
      ElseIf equation.Contains("Cos") Then 
      ElseIf equation.Contains("Sin") Then 
      ElseIf equation.Contains("Tan") Then 

      End If 
     Next 

     txtAnswer.Select(txtAnswer.Text.Length, 0) 

    End Sub 

Private Function Check_Values() As Boolean 



     If operator_count > 1 Then 
      allowed_input = False 
     Else 
      allowed_input = True 
     End If 

     Check_Values = allowed_input 

    End Function 

Answer 1

（-3-3）在这里，你已经有两个“ - ”运营商，因为第一负也作为一个经营者，所以Check_Values处理（）返回假。要解决这个问题，在btnMinus_Click你可以检查减号是不是第一个字符，只有在这种情况下确认operator_count。