Re: Event on Scrolling to the end in flowlayoutpanel - Visual Basic Discussion Boards

Did you recalculate the max value of your scrollbar? if your listbox is of a differed size then mine (witch it probably is) you have to recalculate it.

just run the program. dont scroll and see how many items fit into the listbox (for me that where 18). you want to do the index - [the number you found]. after that it should work.

VB

maxscroll = index - 18 'calculate max value. everytime you add a item you have to do this again. to calculate this its a bit of a trail and error thing depending on your control

Oh that kinda worked... but how am I ganna calculate the value in a control like this one:
When its normal screen size:
http://foto.pk/images/minx.png[^]

When its maximized:
http://foto.pk/images/maxx.png[^]
-------------------------------------------------------------
Btw. You asked why would I want to know this value before...
Answer) I don't actually want to show users "yay u reached the bottom" lol. I want the program to get more tweets when it reaches there.
The above that I am making is a v2 of my current twitter client called TRocket.
TRocket - Twitter Client [Open Source][^]

How do you fill the listbox? with a loop or a data binding?

EDIT:
oke something just shot to my mind. the items you add to your listbox are controls right? i forgot the object name but i've seen the code of those. this means they have a fixed sized right? you could calculate how much fit into your listbox if you read out the length and hight of it.

lets say for example your listbox is 300 pixels wide and 400 pixels high. your controls are 100 wide and 50 high. this would mean you can fit 3 rows of each 8 items = 24 items without scroll bar. so in a 'math' way:

[ammount of items] - (math.floor([with_listbox]/[with_control])+math.floor([hight_listbox]/[hight_control])) = maximum scroll value

-------------------
Ah oke, yea now its making sense Wink | ;)

and i already figured it was for Trocket (read the thread about it) when i was helping you with a previous question.

huh? Sorry but I didn't quiet get that... wasn't quiet good in maths :/
Can you check into the source code:
http://www.mediafire.com/?m13i05h0vmb11yc[^]

I actually want this to be on Flowlayoutpanel1.

VB

Private Function CalculateMaxScrollValue(ByVal totalitems As Int64, ByVal controlhight As Int32, ByVal controlwith As Int32)
        'NOTE: 482 and 114 is the size property of your msgctrl.vb 
        Return totalitems - (Math.Floor(controlwith / 482) * Math.Floor(controlhight / 114))
    End Function

Add that function to your code to find the max scroll value.
Use that in combination with the code i send you in the previous posts in this topic. replace the txtscroll with the flowlayoutpanel1 and it should work (cant test it here).

as a side note: you might want to fine tune the if/else of mine a little to a "<" instead of "=". giving a exact value to a 'analog' control gives it a small change to trigger. also it seems like the program is single threaded. i don't know how long it takes to load those messages but your interface will hang (not responding ect) till the load is complete. looking into threading might be interesting.

Err my laptops fan got fried - is at the repair shop. - sorry for the late reply...
Anyway. So you mean I should just call this function on load? and replace the maxscroll = index - 18 on load?

Hey,

Sorry for my late response. I unfortunately fell ill.
to get back to your question: No, you call that function every time after the amount of items in your flowlayoutpanel changes.

so all the code needs to be same. but what should I do with:
maxscroll = index - 18 ?
the index property was giving an error in flowlayoutpanel. can you give me the example on the same code
or better on the project its self.. :

VB

Imports System.Runtime.InteropServices
 
Public Class Form1
    Dim WithEvents scrollhandler As MyListener 'class that will watch windows to see if your scrolling
    Private scrolled As Boolean = False 'boolean you can use to flip if a message box was displayed or not...(so it wont loop the messagebox.show)
    Private maxscroll As Int64 'int used to store the max value of the scrollbar
    'dll used to get the scrollbar value NOTE: if the scrollbar is not visible or you go higher then your max it will crash!
    <DllImport("user32.dll", CharSet:=CharSet.Auto)> _
    Public Shared Function GetScrollPos(ByVal hWnd As IntPtr, ByVal nBar As Integer) As Integer
    End Function
 
    'dll used to set the scrollbar value NOTE: if the scrollbar is not visible or you go higher then your max it will crash!
    <DllImport("user32.dll")> _
    Private Shared Function SetScrollPos(ByVal hWnd As IntPtr, ByVal nBar As Integer, ByVal nPos As Integer, ByVal bRedraw As Boolean) As Integer
    End Function
 
    Private Const SB_HORZ As Integer = &H0
    Private Const SB_VERT As Integer = &H1
 

    Public Property HScrollPos() As Integer 'property to set or get the horisontal scrollbar value
        Get
            Return GetScrollPos(DirectCast(txtscroll.Handle, IntPtr), SB_HORZ) 'change txtscroll to the control you use. dont forget the .handle
        End Get
        Set(ByVal value As Integer)
            SetScrollPos(DirectCast(txtscroll.Handle, IntPtr), SB_HORZ, value, True) 'change txtscroll to the control you use. dont forget the .handle
        End Set
    End Property
 

    Public Property VScrollPos() As Integer 'Property to set or get the Vertical scrollbar value
        Get
            Return GetScrollPos(DirectCast(txtscroll.Handle, IntPtr), SB_VERT) 'change txtscroll to the control you use. dont forget the .handle
        End Get
        Set(ByVal value As Integer)
            SetScrollPos(DirectCast(txtscroll.Handle, IntPtr), SB_VERT, value, True) 'change txtscroll to the control you use. dont forget the .handle
        End Set
    End Property
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'some random loop i used to ditch some data in my listbox for testing
        Dim index As Int32 = 0
        Do While index < 1000
            txtscroll.Items.Add(index.ToString())
            index += 1
        Loop
        maxscroll = index - 18 'calculate max value. everytime you add a item you have to do this again. to calculate this its a bit of a trail and error thing depending on your control
        'attach your scrollwatcher to your control. in my case i have a listbox called "txtscroll")
        scrollhandler = New MyListener(txtscroll)
 
    End Sub
 
    Private Sub scrollhandler_MyScroll(ByVal sender As Object, ByVal e As System.EventArgs) Handles scrollhandler.MyScroll
        If VScrollPos = maxscroll And scrolled Then 'the scrollbar is down and no message was given, showing a messagebox
            MessageBox.Show("you reached the max on the verticle scrollbar!", "yay")
            scrolled = False 'messagebox was shown, flip bool to prevent loop
        ElseIf VScrollPos < maxscroll Then
            scrolled = True 'the scroll value is smaller then the maximum scroll value. meaning the next time the bar hits the bottem a new textbox should be shown
        End If
    End Sub
 
    Private Sub txtscroll_MouseWheelScroll(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtscroll.MouseWheel
        scrollhandler_MyScroll(e, e) 'needed to catch the scrollwheel event.
    End Sub
 

    Private Class MyListener
        Inherits NativeWindow
 
        Public Event MyScroll(ByVal sender As Object, ByVal e As EventArgs)
        Const WM_MOUSEACTIVATE = &H21
        Const WM_MOUSEMOVE = &H200
        Private control As Control
 
        Public Sub New(ByVal control As Control)
            AssignHandle(control.Handle) 'docks handler to given control
        End Sub
 
        Protected Overrides Sub WndProc(ByRef Messageevent As Message)
            Const WM_HSCROLL = &H114
            Const WM_VSCROLL = &H115
            If Messageevent.Msg = WM_HSCROLL Or Messageevent.Msg = WM_VSCROLL Then 'looks if the horisontal or verticle scrollbar is moving
                'one of the scrollbars is moving, throw event
                RaiseEvent MyScroll(control, New EventArgs)
            End If
            MyBase.WndProc(Messageevent)
        End Sub
 
        Protected Overrides Sub Finalize()
            'not used in example but drops the scroll watcher
            ReleaseHandle()
            MyBase.Finalize()
        End Sub
 
    End Class
 
End Class

hmm oke i admid my code was a bit of mess. i cleared it out a bit and made a example program so you can see how it works. Please follow the below steps.

1. start a new form project
2. Add is Listbox. set the name to txtscroll and the size to 254; 381
3. Add a button, call this one btnadd
4. copy paste the following code into the project (under the form you just made)

VB

Imports System.Runtime.InteropServices

Public Class Form1

#Region "declarations"
    Dim WithEvents scrollhandler As MyListener 'class that will watch windows to see if your scrolling
    Private scrolled As Boolean = False 'boolean you can use to flip if a message box was displayed or not...(so it wont loop the messagebox.show)
    Private maxscroll As Int64 'int used to store the max value of the scrollbar
    Private index As Int32 = 0 'used for random loops to fill the txtscroll
    Private Const SB_HORZ As Integer = &H0
    Private Const SB_VERT As Integer = &H1
#End Region
    

#Region "dll calls"
    'dll used to get the scrollbar value NOTE: if the scrollbar is not visible or you go higher then your max it will crash!
    <DllImport("user32.dll", CharSet:=CharSet.Auto)> _
    Public Shared Function GetScrollPos(ByVal hWnd As IntPtr, ByVal nBar As Integer) As Integer
    End Function

    'dll used to set the scrollbar value NOTE: if the scrollbar is not visible or you go higher then your max it will crash!
    <DllImport("user32.dll")> _
    Private Shared Function SetScrollPos(ByVal hWnd As IntPtr, ByVal nBar As Integer, ByVal nPos As Integer, ByVal bRedraw As Boolean) As Integer
    End Function
#End Region
    
    Public Property HScrollPos() As Integer 'property to set or get the horisontal scrollbar value
        Get
            Return GetScrollPos(DirectCast(txtscroll.Handle, IntPtr), SB_HORZ) 'change txtscroll to the control you use. dont forget the .handle
        End Get
        Set(ByVal value As Integer)
            SetScrollPos(DirectCast(txtscroll.Handle, IntPtr), SB_HORZ, value, True) 'change txtscroll to the control you use. dont forget the .handle
        End Set
    End Property


    Public Property VScrollPos() As Integer 'Property to set or get the Vertical scrollbar value
        Get
            Return GetScrollPos(DirectCast(txtscroll.Handle, IntPtr), SB_VERT) 'change txtscroll to the control you use. dont forget the .handle
        End Get
        Set(ByVal value As Integer)
            SetScrollPos(DirectCast(txtscroll.Handle, IntPtr), SB_VERT, value, True) 'change txtscroll to the control you use. dont forget the .handle
        End Set
    End Property

#Region "form events"
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'some random loop i used to ditch some data in my listbox for testing

        Do While index < 1000
            txtscroll.Items.Add(index.ToString())
            index += 1
        Loop
        
        scrollhandler = New MyListener(txtscroll)
        maxscroll = CalcMaxScroll(txtscroll.Size.Height, txtscroll.Size.Width, 13, 254, txtscroll.Items.Count) 'see my forum post
    End Sub

    Private Sub btnadd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnadd.Click
        'random loop that will add 10 extra items to the listbox
        Dim i As Int32 = index
        Do While i < index + 10
            txtscroll.Items.Add((index + i).ToString())
            i += 1
        Loop
        index += 10
        maxscroll = CalcMaxScroll(txtscroll.Size.Height, txtscroll.Size.Width, 13, 254, txtscroll.Items.Count) 'see my forum post
    End Sub

    Private Sub txtscroll_MouseWheelScroll(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtscroll.MouseWheel
        scrollhandler_MyScroll(e, e) 'needed to catch the scrollwheel event.
    End Sub


    Private Sub scrollhandler_MyScroll(ByVal sender As Object, ByVal e As System.EventArgs) Handles scrollhandler.MyScroll
        If VScrollPos = maxscroll And scrolled Then 'the scrollbar is down and no message was given, showing a messagebox
            MessageBox.Show("you reached the max on the verticle scrollbar!", "yay")
            scrolled = False 'messagebox was shown, flip bool to prevent loop
        ElseIf VScrollPos < maxscroll Then
            scrolled = True 'the scroll value is smaller then the maximum scroll value. meaning the next time the bar hits the bottem a new textbox should be shown
        End If
    End Sub
#End Region

#Region "calculations"
    'see my forum post for more info about this thing
    Private Function CalcMaxScroll(ByVal controlhight As Int32, ByVal controlwith As Int32, ByVal itemhight As Int32, ByVal itemwith As Int32, ByVal totalitems As Int32)
        Return totalitems - (Math.Floor(controlwith / itemwith) * Math.Floor(controlhight / itemhight))
    End Function
#End Region

    
#Region "native scroll listner"
    Private Class MyListener
        Inherits NativeWindow

        Public Event MyScroll(ByVal sender As Object, ByVal e As EventArgs)
        Const WM_MOUSEACTIVATE = &H21
        Const WM_MOUSEMOVE = &H200
        Private control As Control

        Public Sub New(ByVal control As Control)
            AssignHandle(control.Handle) 'docks handler to given control
        End Sub

        Protected Overrides Sub WndProc(ByRef Messageevent As Message)
            Const WM_HSCROLL = &H114
            Const WM_VSCROLL = &H115
            If Messageevent.Msg = WM_HSCROLL Or Messageevent.Msg = WM_VSCROLL Then 'looks if the horisontal or verticle scrollbar is moving
                'one of the scrollbars is moving, throw event
                RaiseEvent MyScroll(control, New EventArgs)
            End If
            MyBase.WndProc(Messageevent)
        End Sub

        Protected Overrides Sub Finalize()
            'not used in example but drops the scroll watcher
            ReleaseHandle()
            MyBase.Finalize()
        End Sub

    End Class
#End Region


End Class

5. run it scroll all the way down, hit the button and scroll down again.

oke now how does it work:
I explained the working of the scroll handlers before so to save some text i'll skip past those in here. the interesting part is in the button klick event. the first few lines is a random loop that will add 10 extra items to my listbox. i gues thats not to interesting, the line following after is.

It will set the maxscroll value to the return of the CalcMaxScroll sub. this sub requires you to give it the following information: The height property of your control. The With property of your control. the Height of the item you send to it (a listbox row is 13 high by default). the With of the item you send to it (in a listbox thats the full with). and the total ammount of items in the listbox. it will return you the maximum scroll position of your scrollbar.

Tought i now use this function with a listbox (i was to lazy to make a new project) it will work perfectly fine aswell with a flowlayout panel. just remember to send all the info to the function and that all the items in the box are the same size. if they aint the same size calculating will get a little harder....but not impossible.

ps: just put a breakpoint on the button klick event and watch what happends after the loop. keep the breakpoint on and scroll a bit. things get pretty clear once you see it running.

Alright so here is what I got so far:

VB

Dim WithEvents scrollhandler As MyListener 'class that will watch windows to see if your scrolling
    Private scrolled As Boolean = False 'boolean you can use to flip if a message box was displayed or not...(so it wont loop the messagebox.show)
    Private maxscroll As Int64 'int used to store the max value of the scrollbar
    '   Private index As Int32 = 0 'used for random loops to fill the txtscroll
    Private Const SB_HORZ As Integer = &H0
    Private Const SB_VERT As Integer = &H1

    'dll used to get the scrollbar value NOTE: if the scrollbar is not visible or you go higher then your max it will crash!
    <DllImport("user32.dll", CharSet:=CharSet.Auto)> _
    Public Shared Function GetScrollPos(ByVal hWnd As IntPtr, ByVal nBar As Integer) As Integer
    End Function

    'dll used to set the scrollbar value NOTE: if the scrollbar is not visible or you go higher then your max it will crash!
    <DllImport("user32.dll")> _
    Private Shared Function SetScrollPos(ByVal hWnd As IntPtr, ByVal nBar As Integer, ByVal nPos As Integer, ByVal bRedraw As Boolean) As Integer
    End Function


    Public Property HScrollPos() As Integer 'property to set or get the horisontal scrollbar value
        Get
            Return GetScrollPos(DirectCast(FlowLayoutPanel1.Handle, IntPtr), SB_HORZ) 'change txtscroll to the control you use. dont forget the .handle
        End Get
        Set(ByVal value As Integer)
            SetScrollPos(DirectCast(FlowLayoutPanel1.Handle, IntPtr), SB_HORZ, value, True) 'change txtscroll to the control you use. dont forget the .handle
        End Set
    End Property


    Public Property VScrollPos() As Integer 'Property to set or get the Vertical scrollbar value
        Get
            Return GetScrollPos(DirectCast(FlowLayoutPanel1.Handle, IntPtr), SB_VERT) 'change txtscroll to the control you use. dont forget the .handle
        End Get
        Set(ByVal value As Integer)
            SetScrollPos(DirectCast(FlowLayoutPanel1.Handle, IntPtr), SB_VERT, value, True) 'change txtscroll to the control you use. dont forget the .handle
        End Set
    End Property

    'will add load in the end.

    Private Sub FlowLayoutPanel1_MouseWheelScroll(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles FlowLayoutPanel1.MouseWheel
        scrollhandler_MyScroll(e, e) 'needed to catch the scrollwheel event.
    End Sub


    Private Sub scrollhandler_MyScroll(ByVal sender As Object, ByVal e As System.EventArgs) Handles scrollhandler.MyScroll
        If VScrollPos = maxscroll And scrolled Then 'the scrollbar is down and no message was given, showing a messagebox
            MessageBox.Show("you reached the max on the verticle scrollbar!", "yay")
            scrolled = False 'messagebox was shown, flip bool to prevent loop
        ElseIf VScrollPos < maxscroll Then
            scrolled = True 'the scroll value is smaller then the maximum scroll value. meaning the next time the bar hits the bottem a new textbox should be shown
        End If
    End Sub

    Private Function CalcMaxScroll(ByVal controlhight As Int32, ByVal controlwith As Int32, ByVal itemhight As Int32, ByVal itemwith As Int32, ByVal totalitems As Int32)
        Return totalitems - (Math.Floor(controlwith / itemwith) * Math.Floor(controlhight / itemhight))
    End Function

    Private Class MyListener
        Inherits NativeWindow

        Public Event MyScroll(ByVal sender As Object, ByVal e As EventArgs)
        Const WM_MOUSEACTIVATE = &H21
        Const WM_MOUSEMOVE = &H200
        Private control As Control

        Public Sub New(ByVal control As Control)
            AssignHandle(control.Handle) 'docks handler to given control
        End Sub

        Protected Overrides Sub WndProc(ByRef Messageevent As Message)
            Const WM_HSCROLL = &H114
            Const WM_VSCROLL = &H115
            If Messageevent.Msg = WM_HSCROLL Or Messageevent.Msg = WM_VSCROLL Then 'looks if the horisontal or verticle scrollbar is moving
                'one of the scrollbars is moving, throw event
                RaiseEvent MyScroll(control, New EventArgs)
            End If
            MyBase.WndProc(Messageevent)
        End Sub

        Protected Overrides Sub Finalize()
            'not used in example but drops the scroll watcher
            ReleaseHandle()
            MyBase.Finalize()
        End Sub

    End Class


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

        scrollhandler = New MyListener(FlowLayoutPanel1)
        maxscroll = CalcMaxScroll(FlowLayoutPanel1.Size.Height, FlowLayoutPanel1.Size.Width, 114, 1075, 19)

        '19 number of tweets
        '114 height of tweettimelinecontrol
        '1075 width of flowlayoutpanel1
        'last number tells the number of items. (read that from a global var)

    End Sub

Source code also attached:
http://www.mediafire.com/?m63ox9sllr887dd[^]

I am pretty sure I am doing everything right... but its just not working with flowlayoutpanel :/

It seems your making a mistake in providing the arguemnts for your max scroll.

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

scrollhandler = New MyListener(FlowLayoutPanel1)
maxscroll = CalcMaxScroll(FlowLayoutPanel1.Size.Height, FlowLayoutPanel1.Size.Width, 114, 1075, 19)

'19 number of tweets
'114 height of tweettimelinecontrol
'1075 width of flowlayoutpanel1
'last number tells the number of items. (read that from a global var)

End Sub

You say that the with of your flowlayoutpanel is 1075. yet you apply it to the formula as the with of your tweettimelinecontrol. quoting you from a previous post:

Quote:

Oh that kinda worked... but how am I ganna calculate the value in a control like this one:
When its normal screen size:
http://foto.pk/images/minx.png[^]

you can see in the screenshot that you got 2 of those controls next to eachoter so it can never be the total size of your flowlayoutpanel. please check the with property of your Tweettimelinecontrol and change the value. while your at it also change the 19 with a flowlayoutpanel.items.count to make sure it are 19.

private int previousValue;

public void someEventHandler(...) {
    int currentValue=...;
    if (currentValue==extremeValue && currentValue!=previousValue) doWhatEver();
    previousValue=currentValue;
}

Luc Pattyn [My Articles] Nil Volentibus Arduum

oeh quite nice! might actually try that in the future. but isn't that C#?

I'd call it pseudo-code around here Big Grin | :-D

Luc Pattyn [My Articles] Nil Volentibus Arduum

1-0 for you Wink | ;)

isn't previousValue a readonly value?

did I declare it read-only? Confused | :confused:

Luc Pattyn [My Articles] Nil Volentibus Arduum

Seems like I misunderstood the algorithm.

Hi everyone,

I am currently working on developing some code for transfer file from one pc to another. As I read in lot of article, those work can be done by FTP concept.

I'm using win7 and VB.NET 2010

I've got some simple source code for uploading a file, but I'm experiencing a problem which describe below

VB

System.ArgumentNullException was unhandled
  Message=Value cannot be null.
Parameter name: type
  ParamName=type
  Source=mscorlib

it's refers to:

ITCObject = Activator.CreateInstance(ITC)

Here are the source code:

Imports System.IO
Imports System.Reflection
Imports System.Threading

Public Class Main

    Private Sub btnBrowse_Click(ByVal sender As System.Object, e As System.EventArgs) Handles btnBrowse.Click
        OpenFileDialog.ShowDialog()
        tbFile.Text = OpenFileDialog.FileName
    End Sub

    Private Sub btnUpload_Click(ByVal sender As System.Object, e As System.EventArgs) Handles btnUpload.Click
        Dim thisFile As FileInfo = New FileInfo(tbFile.Text)
        Dim ITC As Type
        Dim parameter() As Object = New Object(1) {}
        Dim ITCObject As Object
        ITC = Type.GetTypeFromProgID("InetCtls.Inet")
        ITCObject = Activator.CreateInstance(ITC)
        parameter(0) = CType(tbRemoteServer.Text, String)
        parameter(1) = CType("PUT " + thisFile.FullName + " /" + thisFile.Name, String)
        ITC.InvokeMember("execute", BindingFlags.InvokeMethod, Nothing, ITCObject, parameter)
    End Sub
End Class

is there anyone could help me to resolve this problem.

Thx,
Phann

That means:
ITC = Type.GetTypeFromProgID("InetCtls.Inet")
returned null.
But tell us: why do you need Refelection for FTP?

what do you mean by

Bernhard Hiller wrote:
Refelection for FTP?

I'm really not quite sure.. but it came with the source code.. and it has related with "BindingFlags.InvokeMethod".

I'm still having difficulty to figure out the source code and how it works..

Compare your code with the sample here[^].

Bastard Programmer from Hell Suspicious | :suss:

done with the solution at link below:

http://windowsdevcenter.com/pub/a/windows/2006/12/12/building-ftp-services-using-net-20.html?page=1[^]

case closed..
thx a lot for all sugestion

[b]Hello everyone.[/b]
I am trying to create a basic project in vb.net. In this project i have a richtextbox with name editingarea and a button with name button1.

I just want that when the button1 is clicked a font selection dialog box will open where the user can select the font name and size. then set this font for rich text box.

But I am getting some kind of error as "Property name is read only", "Property size is read only", after setting the readonly property to false too.
Here is the code

VB

If SelectFont.ShowDialog = Windows.Forms.DialogResult.OK Then

            EditingArea.Font.Name = SelectFont.Font.Name
            EditingArea.Font.Size = SelectFont.Font.Size

        End If

Can someone help me out.
[b]Thanks[/b]