[RESOLVED] [2005] insert item into a custom listview in tabpage

[kahwai1984]

thx jmcilhinney on this thread Question in create tabpage with same component
ok... now i had found another problem base on the thread above and hope got someone to help.

After declare class and inherit the TabPage class, and in the constructor create a ListView. How do i add an item into a specific listview?
for example i wan to add an item "ABC" into tabpage(2)---->listview.

[kebo]

one way would be to make the listview a public member of the tab page then refence it throught the tab page....

Public Class TabPageEx
    Inherits TabPage
    Public lv as ListView 'define the list view member here
    Public Sub New()
        lv = New ListView 'then instance the listview member here
        Dim clmcode As New ColumnHeader
        Dim symbol As New ColumnHeader
 
        symbol.Text = "Symbol"
        clmcode.Text = "Code"
        With lv
            .Name = "hello"    <--- the name did not display
            .BorderStyle = System.Windows.Forms.BorderStyle.None
            .MultiSelect = True
            .Columns.AddRange(New ColumnHeader() {clmcode, symbol})
            .Dock = System.Windows.Forms.DockStyle.Fill
            .FullRowSelect = True
            .GridLines = True
            .View = System.Windows.Forms.View.Details
        End With
        Me.Controls.Add(lv)
    End Sub
End Class

then you should be able to get to the listview using something like

tabpage(2).lv.add(myListViewItem)

kevin

[jmcilhinney]

While what kebo suggested will work I'd actually suggest modifying it a bit. First of all, at most you should expose the ListView via a ReadOnly field:

Public ReadOnly ListView As ListView

That way a new ListView object cannot be assign to the field from outside, or even inside other than in the constructor. I'd consider it better to use a ReadOnly property:

Private _listView As ListView
 
Public ReadOnly Property ListView() As ListView
    Get
        Return Me._listView
    End Get
End Property

That said, I would think that the only thing you'd need to access from outside the TabPage would be the Items collection of the ListView. In that case that is the only thing you should expose:

Private _listView As ListView
 
Public ReadOnly Property Items() As ListViewItemCollection
    Get
        Return Me._listView.Items
    End Get
End Property

Now no aspect of the ListView can be affected from outside other than the items.

[kahwai1984]

thx kebo... i try ur method and and it works. anywhere thx jmcilhinney's suggestion also.
now i have face another new problem:

how i know which listview i am controlling? i had a timer + backgroundworker to keep updating the data.
And if i change another tab, only the listview in selectedtab will keep updating the data?

[jmcilhinney]

If only the ListView on the selected tab is being updated then that's because you're only updating the ListView on the selected tab. If you want the ListView on all the tabs to update then obviously you have to update the ListView's on all the tabs. If you have N tabs then you have to run your update code N times, once For Each tab in the TabControl.

[kahwai1984]

If only the ListView on the selected tab is being updated then that's because you're only updating the ListView on the selected tab. If you want the ListView on all the tabs to update then obviously you have to update the ListView's on all the tabs. If you have N tabs then you have to run your update code N times, once For Each tab in the TabControl.

No No... i think you had misunderstood..., i just wan to update the specific listview in the selectedtab. Your method also a good idea... if i use ur method, how to update the listview? how do i identify that the listview is the listview in that tab? Because the listview i update not during creating time, but in a backgroundworker event...

THE MOST IMPORTANT IS HOW I GET THE LISTVIEW OBJECCT
if can get the object i maybe will have idea on the next step.
Sorry that i am new to VB.net. Hope someone can help me

[jmcilhinney]

The SelectedTab is the TabPage that's selected. If you want the ListView on the selected TabPage then you get the SelectedTab first, then get the ListView on that page. Assuming that you chose to use the second code snippet post #3 that would look like this:

Dim selectedListView As ListView = DirectCast(myTabControl.SelectedTab, TabPageEx).ListView

where TabPageEx is your extended TabPage class that displays its own ListView.

[kahwai1984]

As i not quite sure about second code snippet post #3, so i had use kobe method on the post #2, with your solution:

Dim selectedListView As ListView = DirectCast(myTabControl.SelectedTab, TabPageEx).ListView

but if i put this in background worker will have a cross-thread problem, and if i invoke it, the whole system will slow responds... below are the code:

Private Sub StreamStockDataWorker_DoWork(ByVal sender As System.Object, _
    ByVal e As System.ComponentModel.DoWorkEventArgs) Handles StreamStockDataWorker.DoWork
       If TabControl1.InvokeRequired = True Then
            Dim Invoker As New MethodInvoker(AddressOf SelectTab)
           TabControl1.Invoke(Invoker)
        End If
    End Sub
 
    Private Sub SelectTab()
        Dim selectedListView As ListView = DirectCast(TabControl1.SelectedTab, TabPageEx).lv
        Dim i As Integer
        Dim EmptyData As Integer
        Dim stockdata As StockData
        Dim datastock As String()
        For i = 0 To selectedListView.Items.Count - 1
            datastock = client1.DownloadString("link" & selectedListView.Items(i).Text).Split("|")
            stockdata.name = datastock(3)
            stockdata.open = datastock(6)
            With selectedListView.Items(i).SubItems
                   .Add(stockdata.name)
                   .Add(stockdata.open)
            End With
        Next
     End Sub

any solution for this? if can, it is better not for me to put invoke... anyway to put

Dim selectedListView As ListView = DirectCast(TabControl1.SelectedTab, TabPageEx).lv

in backgroundworker and does not have cross-thread problem?

[jmcilhinney]

There's no need for you to be marshaling back to the UI thread at all. You can get all the information you need before you start the BackgroundWorker, do all the work in the background thread and collect the results, then update the UI after the worker completes:

Private Sub InitiateBackgroundTask()
    'This can be any object you want, so it can contain any and as much data as you like.
    Dim argument As Object
 
    'Populate argument here.
 
    Me.BackgroundWorker1.RunWorkerAsync(argument)
End Sub
 
 
Private Sub BackgroundWorker1_DoWork(ByVal sender As Object, _
                                     ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
    'Get the starting data back here.
    Dim argument As Object = e.Argument
 
    'This can be any object you want, so it can contain any and as much data as you like.
    Dim result As Object
 
    'Use argument and populate result here.
 
    e.Result = result
End Sub
 
Private Sub BackgroundWorker1_RunWorkerCompleted(ByVal sender As Object, _
                                                 ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
    'Get the result data back here.
    Dim result As Object = e.Result
 
    'Use result here.
End Sub

So you see, you get all the data you need from the ListView BEFORE you ever start the background thread and you don't update the UI until AFTER the background thread has completed, so there's never any delegation required. If you really want to update the UI as you go then you can call the BGW's ReportProgress method and update the UI in the ProgressChanged event handler. See here for more info.

[kahwai1984]

i think i need to explain what am i trying to do:
i am doing a stock quote monitoring function.
When form load, there will be a list of data from database display to a listbox. Then when user double click the item, a tabpage will be generated and a list of data will also generated into the listview. Base on the item in the listview, data will be downloaded and added into listview.subitem. i plan to do all this in background. The first problem i face was cross thread problem like below code:

Private Sub InitiateBackgroundTask()
        Dim selectedListView As ListView
 
        selectedListView = DirectCast(TabControl1.SelectedTab, TabPageEx).lv
 
        StreamStockDataWorker.RunWorkerAsync(selectedListView)
    End Sub
 
    Private Sub StreamStockDataWorker_DoWork(ByVal sender As System.Object, _
    ByVal e As System.ComponentModel.DoWorkEventArgs) Handles StreamStockDataWorker.DoWork
        If TabControl1.TabPages.Count = 0 Then
        Else
            Dim i As Integer
            Dim WholeListview As ListView = e.Argument
            Dim EmptyData As Integer
            Dim stockdata As StockData
            Dim datastock As String()
            For i = 0 To WholeListview.Items.Count - 1
                Dim abc As String
                abc = WholeListview.Items(i).Text        <-----cross-thread error
                datastock = datastock = client1.DownloadString("link" & selectedListView.Items(i).Text).Split("|")
            stockdata.name = datastock(3)
            stockdata.open = datastock(6)
            With selectedListView.Items(i).SubItems
                   .Add(stockdata.name)
                   .Add(stockdata.open)
            End With
            Next
        End If
    End Sub

[jmcilhinney]

I have already explained what you need to do.

[kahwai1984]

I had try another way like this:

Private Sub InitiateBackgroundTask()
        Dim selectedListView As ListView = DirectCast(TabControl1.SelectedTab, TabPageEx).lv
 
For i = 0 To selectedListView.Items.Count - 1
        Dim name As String = selectedListView.Items(i).Text
        StreamStockDataWorker.RunWorkerAsync(name)
Next
 
Private Sub StreamStockDataWorker_DoWork(ByVal sender As System.Object, _
    ByVal e As System.ComponentModel.DoWorkEventArgs) Handles StreamStockDataWorker.DoWork
        Dim name As String = e.Argument
        Dim datastock As String()
        If TabControl1.TabPages.Count = 0 Then
 
        Else
            datastock = client1.DownloadString("link" & name.Tostring).Split("|")
        End If
    End Sub

but obviously, this will occured "backgroundworker cannot handle concurren task" problem...

[jmcilhinney]

Have I got any loop in my InitiateBackgroundTask method? No, I don't. What did I say in my last post?

you get all the data you need from the ListView BEFORE you ever start the background thread

If you have 100 items in your ListView and you need a value from each of them then you get a avlue from each item first, THEN you start the background thread and pass in ALL the data. You process ALL the data in your DoWork event handler, collecting ALL the data you need to ouput and passing it ALL out. Finally you update the UI with ALL the data you passed out at the end of the DoWork event handler.

[kahwai1984]

thanks jmcilhinney. Now i had another problem base on the listview above. How do i handle double click event for a specific listview?

[jmcilhinney]

thanks jmcilhinney. Now i had another problem base on the listview above. How do i handle double click event for a specific listview?

This is a completely different topic and should be discussed in its own thread. One thread per topic and one topic per thread please.