odd behaviour double click label v button

[Neil Wallace]

Hi,

This is an odd one. I've been struggling to get "double click" to work well
for my controls.

The same event handler works perfectly for buttons, but not for labels.

Can anyone tell me why not?

Below is an working VB.Net example to illustrate what I mean.

regards

Neil.

Public Class Form1

Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

Public Sub New()

MyBase.New()

'This call is required by the Windows Form Designer.

InitializeComponent()

'Add any initialization after the InitializeComponent() call

End Sub

'Form overrides dispose to clean up the component list.

Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)

If disposing Then

If Not (components Is Nothing) Then

components.Dispose()

End If

End If

MyBase.Dispose(disposing)

End Sub

'Required by the Windows Form Designer

Private components As System.ComponentModel.IContainer

'NOTE: The following procedure is required by the Windows Form Designer

'It can be modified using the Windows Form Designer.

'Do not modify it using the code editor.

Friend WithEvents Label1 As System.Windows.Forms.Label

Friend WithEvents Button1 As System.Windows.Forms.Button

Friend WithEvents Label2 As System.Windows.Forms.Label

Friend WithEvents Label3 As System.Windows.Forms.Label

Friend WithEvents Timer1 As System.Windows.Forms.Timer

<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()

Me.components = New System.ComponentModel.Container

Me.Label1 = New System.Windows.Forms.Label

Me.Button1 = New System.Windows.Forms.Button

Me.Label2 = New System.Windows.Forms.Label

Me.Label3 = New System.Windows.Forms.Label

Me.Timer1 = New System.Windows.Forms.Timer(Me.components)

Me.SuspendLayout()

'

'Label1

'

Me.Label1.BackColor = System.Drawing.Color.FromArgb(CType(255, Byte),
CType(128, Byte), CType(128, Byte))

Me.Label1.Location = New System.Drawing.Point(192, 104)

Me.Label1.Name = "Label1"

Me.Label1.Size = New System.Drawing.Size(80, 23)

Me.Label1.TabIndex = 0

Me.Label1.Text = "Label"

Me.Label1.TextAlign = System.Drawing.ContentAlignment.MiddleCenter

'

'Button1

'

Me.Button1.BackColor = System.Drawing.Color.FromArgb(CType(255, Byte),
CType(128, Byte), CType(128, Byte))

Me.Button1.Location = New System.Drawing.Point(24, 104)

Me.Button1.Name = "Button1"

Me.Button1.TabIndex = 1

Me.Button1.Text = "Button"

'

'Label2

'

Me.Label2.Font = New System.Drawing.Font("Microsoft Sans Serif", 14.25!,
System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, CType(0,
Byte))

Me.Label2.ForeColor = System.Drawing.SystemColors.ControlText

Me.Label2.Location = New System.Drawing.Point(40, 24)

Me.Label2.Name = "Label2"

Me.Label2.Size = New System.Drawing.Size(216, 48)

Me.Label2.TabIndex = 2

Me.Label2.Text = "Double Click Successful"

Me.Label2.TextAlign = System.Drawing.ContentAlignment.MiddleCenter

Me.Label2.Visible = False

'

'Label3

'

Me.Label3.Location = New System.Drawing.Point(40, 152)

Me.Label3.Name = "Label3"

Me.Label3.Size = New System.Drawing.Size(208, 80)

Me.Label3.TabIndex = 3

Me.Label3.Text = "Try double clicking on the button and the label. Both have
the same event handle" & _

"r. However, the label doesn't behave as anticipated and for some reason
requires" & _

" a ""triple click""."

Me.Label3.TextAlign = System.Drawing.ContentAlignment.MiddleCenter

'

'Timer1

'

Me.Timer1.Interval = 200

'

'Form1

'

Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)

Me.ClientSize = New System.Drawing.Size(292, 266)

Me.Controls.Add(Me.Label3)

Me.Controls.Add(Me.Label2)

Me.Controls.Add(Me.Button1)

Me.Controls.Add(Me.Label1)

Me.Name = "Form1"

Me.Text = "Form1"

Me.ResumeLayout(False)

End Sub

#End Region

Dim lastclicktime As DateTime

Dim lastclicked As String

Dim waittwoticks As Integer

Private Sub Double_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs)

'the equals checks if the sender is the same as the last clicked control
i.e. "button" or "label"

'also check if two events on the same control have occurred within the
allowed time period.

If Equals(lastclicked, sender.text) And
Now.Subtract(lastclicktime).TotalMilliseconds <
Windows.Forms.SystemInformation.DoubleClickTime Then

'if they have then show the "double click" label

Label2.Visible = True

Else : Label2.Visible = False

End If

lastclicked = sender.text

lastclicktime = Now

End Sub

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

AddHandler Label1.Click, AddressOf Me.Double_Click

AddHandler Button1.Click, AddressOf Me.Double_Click

Timer1.Start()

End Sub

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

If Label2.Visible = True Then

If waittwoticks = 3 Then

Label2.Visible = False

Else : waittwoticks += 1

End If

Else : waittwoticks = 0

End If

End Sub

End Class

 

[Cor Ligthert]

Neil,

The double click work for almost every control different. There is a special
page on MSDN for that, I have not a link direct to it, and because in this
case I don't know the search string can you maybe look for it yourself.

Cor

 

[Chris Dunaway]

Here is the link:

http://tinyurl.com/3hvox

But I wonder why the OP is not just subscribing to the DoubleClick
event of the label?

Chris

 

[Neil Wallace]

Here is the link:

http://tinyurl.com/3hvox

But I wonder why the OP is not just subscribing to the DoubleClick
event of the label?

Chris

thanks Cor and Chris.

That table does pose more questions than answers.

My understanding was that there was no such thing as a "doubleclick" event
for either a label or a button, hence the need to check programatically for
the elapsed time between two consecutive clicks.
Now we find the CLR interprets the exact same code differently depending on
the nature of the sender?

IMHO that is an example of managed code removing the rights of the
programmer.

I would love to know the reasoning behind this.