Question

我试图使用一个按钮运行3个计时器，每次点击1个计时器都会运行。它在第二个计时器运行顺利，但在第3次点击第3个计时器没有运行。任何人都可以帮我这个吗？

这是我的代码

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        If Timer1.Enabled = False Then
            Timer1.Start()
        ElseIf Timer1.Enabled = True Then
            Timer2.Start()
        ElseIf Timer1.Enabled = True And
            Timer2.Enabled = true Then
            Timer3.Start()

        End If

    End Sub

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        Label1.Text = Label1.Text + 1
        If Label1.Text = 60 Then
            Label1.Text = 0
            Label2.Text += 1
        ElseIf Label2.Text = 60 Then
            Label2.Text = 0
            Label3.Text += 1
        End If

    End Sub

    Private Sub Timer2_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer2.Tick
        Label6.Text = Label6.Text + 1
        If Label6.Text = 60 Then
            Label6.Text = 0
            Label5.Text += 1
        ElseIf Label5.Text = 60 Then
            Label5.Text = 0
            Label4.Text += 1
        End If

    End Sub
    Private Sub Timer3_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer3.Tick
        Label12.Text = Label12.Text + 1
        If Label12.Text = 60 Then
            Label12.Text = 0
            Label11.Text += 1
        ElseIf Label11.Text = 60 Then
            Label11.Text = 0
            Label10.Text += 1
        End If

    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub
End Class

Answer 1

代码中的问题在范围内，如果在（IF，ELSE IF，ELSE IF，ELSE）语句中找到一个条件，则代码将在该范围内输入，并且不会检查其他条件。例如，

IF (CONDITION)
..some code
ELSE IF(CONDITION) // if this condition is found true, then compiler will not check other condtion
..some code // this code will be executed only
ELSE IF(CONDITION)
..some code
ELSE
..some code

首先确保所有功能都启用为true或false，并按如下所示更改代码：

     If Timer1.Enabled = False And Timer2.Enabled = False And  Timer3.Enabled=False Then
            Timer1.Start()
     End If
     If Timer1.Enabled = True And Timer2.Enabled = False And  Timer3.Enabled=False Then
            Timer2.Start()
     End If
     If Timer1.Enabled = True And Timer2.Enabled=True And Timer3.Enabled=False Then
            Timer3.Start()
     End If

Answer 2

您需要了解If和ElseIf之间的区别

如果第一个条件匹配，它将不会进入下一个检查条件，因此在这种情况下，此代码必须像这样替换

If Timer1.Enabled = False Then
    Timer1.Start()
End If

If Timer1.Enabled = True Then
    Timer2.Start()
End If  

If Timer1.Enabled = True And Timer2.Enabled = true Then
    Timer3.Start()
End If

修改

根据你的评论你可以做这样的事情

Public Class Form1
    Dim ClickCount as Integer 
    ClickCount = 0
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        ClickCount = ClickCount + 1
        If Timer1.Enabled = False and ClickCount = 1 Then
            Timer1.Start()
        ElseIf Timer1.Enabled = True and ClickCount = 2 Then
            Timer2.Start()
        ElseIf Timer1.Enabled = True And Timer2.Enabled = true and ClickCount = 3  Then
            Timer3.Start()
            ClickCount = 0;
        End If
    End Sub

Answer 3

您的代码永远不会进入第二个ElseIf。从第三次单击按钮开始，语句Timer1.Enabled = True仍为真，它将进入该部分代码。这使得该部分能够使第三个计时器无法访问。

你真正想要的是什么：

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles Button1.Click

        If Timer1.Enabled = True And Timer2.Enabled = True Then
            Timer3.Start()
        ElseIf Timer1.Enabled = True Then
            Timer2.Start()
        Else 
            Timer1.Start()
        End If

    End Sub

    Private Sub Timer1_Tick(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles Timer1.Tick

        Label1.Text = Label1.Text + 1
        If Label1.Text = 60 Then
            Label1.Text = 0
            Label2.Text += 1
        ElseIf Label2.Text = 60 Then
            Label2.Text = 0
            Label3.Text += 1
        End If

    End Sub

    Private Sub Timer2_Tick(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles Timer2.Tick

        Label6.Text = Label6.Text + 1
        If Label6.Text = 60 Then
            Label6.Text = 0
            Label5.Text += 1
        ElseIf Label5.Text = 60 Then
            Label5.Text = 0
            Label4.Text += 1
        End If

    End Sub
    Private Sub Timer3_Tick(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles Timer3.Tick

        Label12.Text = Label12.Text + 1
        If Label12.Text = 60 Then
            Label12.Text = 0
            Label11.Text += 1
        ElseIf Label11.Text = 60 Then
            Label11.Text = 0
            Label10.Text += 1
        End If

    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub
End Class

Answer 4

你的第二个ElseIf的条件和第三个ElseIf的第一部分是相同的，这意味着第三个从不执行其中的代码，因为它总是落入第二个条件。

这将使您的代码更容易保存变量以跟踪您需要启动的计时器。此外，如果您使用案例陈述，那么添加更多的定时器是一项简单的任务。

这样的事情：

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'declare a static variable which keeps its value
        Static whichTimer As Integer = 0
        'every time the button is clicked increment the value
        whichTimer += 1

        'now start the appropriate timer
        Select Case whichTimer
            Case 1
                Timer1.Start()
            Case 2
                Timer2.Start()
            Case 3
                Timer3.Start()
            Case Else
                'don't care
        End Select

End Sub

VB.NET如果在Timer中发出ElseIf问题

4 个答案: