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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