vb.net 教程 3-11 窗体控件综合编程 1

通过之前的学习，大家对窗体和控件知识已经有了初步的理解，本节开始将进行一些综合编程训练。

先从简单开始，综合编程1 计算器。

先考虑一下计算器的设计，可以参考windows的计算器。最基本那种就可以了。

下面是一个计算器控件摆放和命名：



txtValue的readonly属性设置为true；按钮的FlatStyle属性设置为Popup。

代码比较容易懂，我直接给出来：

'做运算的第一个数字
Dim numFirst As Double
'做运算的第二个数字
Dim numSecond As Double
'运算符号
Dim operatesymbol As String

'清除
Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click
txtValue.Text = "0"
operatesymbol = ""
End Sub

'删除最后一个数字
Private Sub btnBack_Click(sender As Object, e As EventArgs) Handles btnBack.Click
If txtValue.Text.Length = 1 Then
txtValue.Text = "0"
ElseIf txtValue.Text.Length > 1 Then
txtValue.Text = txtValue.Text.Substring(0, txtValue.Text.Length - 1)
End If
End Sub

'按下数字按钮
Private Sub btn1_Click(sender As Object, e As EventArgs) Handles _
btn1.Click, btn2.Click, btn3.Click,
btn4.Click, btn5.Click, btn6.Click,
btn7.Click, btn8.Click, btn9.Click
Dim btnclick As Button = CType(sender, Button)
Dim addnumber As String = btnclick.Text
Select Case txtValue.Text
Case "0"
txtValue.Text = addnumber
Case "-0"
txtValue.Text = "-" & addnumber
Case Else
txtValue.Text &= addnumber
End Select
End Sub

'按下小数点
Private Sub btnDot_Click(sender As Object, e As EventArgs) Handles btnDot.Click
txtValue.Text &= "."
End Sub

'按下正负号按钮
Private Sub btnNegPos_Click(sender As Object, e As EventArgs) Handles btnNegPos.Click
If txtValue.Text.Substring(0, 1) = "-" Then
txtValue.Text = txtValue.Text.Substring(1, txtValue.Text.Length - 1)
Else
txtValue.Text = "-" & txtValue.Text
End If
End Sub

'按下运算符按钮
Private Sub btnOperate_Click(sender As Object, e As EventArgs) Handles btnAdd.Click, btnSub.Click, btnDiv.Click, btnMul.Click
Dim btnclick As Button = CType(sender, Button)
numFirst = Double.Parse(txtValue.Text)
operatesymbol = btnclick.Text
txtValue.Text = "0"
End Sub

'按下等于按钮
Private Sub btnEqual_Click(sender As Object, e As EventArgs) Handles btnEqual.Click
numSecond = Double.Parse(txtValue.Text)
Dim dbValue As Double

Select Case operatesymbol
Case "+"
dbValue = numFirst + numSecond
Case "-"
dbValue = numFirst - numSecond
Case "*"
dbValue = numFirst * numSecond
Case "/"
dbValue = numFirst / numSecond
Case ""
Exit Sub
Case Else
Exit Sub
End Select
Dim strValue As String = dbValue.ToString

txtValue.Text = strValue
End Sub

'按下平方按钮
Private Sub btnSquare_Click(sender As Object, e As EventArgs) Handles btnSquare.Click
Dim btnclick As Button = CType(sender, Button)
numFirst = Double.Parse(txtValue.Text)

Dim dbValue As Double
dbValue = numFirst ^ 2
Dim strValue As String = dbValue.ToString

txtValue.Text = strValue
End Sub

也显而易见代码中还存在些bug，请试着改正：

1、运行完毕后，数字按钮按下将会添加到运算结果后面；

2、数字除以0或者结果超大的时候会显示“正无穷大”，任然可以参与运算，但是会导致错误；

3、多次按下运算符会导致误认为第一个做计算的数字为0，导致结果不正确。

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