I have a problem that I and my limited experience cannot figure out.
I have a multi-display (form) program that is for a game show system which uses a (5) display system. As I am wrapping this project up, I have been doing some house keeping and handling some potential user errors up front.
In this instance: There is a form called GameSetup which has drop down menus that are filled via a database selection of "Teams". When a Team is selected, (10) labels are populated with registered team members. The user drags and drops a team member (ie. player) to a group of (6) labels, which will make up the active team for the game.
The problem: I wanted to have a check when a name is added to the active team roster to make sure there are no duplicates. The cleanest way to do this, I thought, would be on the .TextChanged action of the active player label and use a For loop to check the other active team player names.
Private Sub lblT1_P1_TextChanged(sender As Object, e As EventArgs) Handles lblT1_P1.TextChanged
cmdReady.BackColor = Color.Yellow
For i = 1 To 6
If i = 1 Then
' Do nothing
ElseIf Me.Controls("lblT1_P" & i.ToString).Text = lblT1_P1.Text Then 'This is the line triggering the NullException
MsgBox("This Player is already selected. Please choose another Player", MsgBoxStyle.OkOnly)
Me.Controls("lblT1_P" & i.ToString).Text = "DRAG PLAYER HERE" 'This is the other line triggering the NullException
End If
Next i
End Sub
i = 1 Do Nothing is so that it wont compare against itself (in this instance)
When I run the program (de-bug), before the form GameSetup loads, I am getting a Null Exception, which makes sense as it is looking at a form or an object in a form that is not yet initialized. Clearly, the Me.Controls is the problem, but I do not know how to handle using the integer (i) in the For Loop otherwise.
The label names are lblT1_P1 - lblT1_P6 (3 instance of each group (T1/T2/T3). I'm only dealing with T1_P1 at the moment.
Any suggestion would be greatly appreciated.
Use string.Format() to generate your control names, because it is more readable.
Instead of Me.controls("lblName").Text
use DirectCast(Me.FindControl("lblName"), Label).Text
Related
I am creating a custom floating number pad so that tablet users can more easily tap numerical data into a form. I'm using toggle buttons (the idea is to eventually highlight them briefly). The following code for the number pad works on my main form's controls. When I click on the 1 button, then a 1 is put into the active control of the main form
Private Sub Form_Activate()
FocusForm = Application.Screen.PreviousControl.Parent.Name
FocusControl = Application.Screen.PreviousControl.Name
End Sub
Private Sub Toggle1_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
'Add a 1 to the currently selected control
Dim refControl As Control
If FocusForm = "" Then End
Set refControl = Forms(FocusForm).Controls(FocusControl)
If (IsNull(refControl)) Then
refControl = "1"
Else
refControl.Text = refControl.Text & "1"
End If
refControl.SetFocus
End Sub
However, if I navigate into the subform then the Screen.PreviousControl properties return the main form's name and the subform's name, but I can't then seem to be able to refer to the subform control's name as well. Bascially I'm looking for a line that does the following
FocusForm = Application.Screen.PreviousControl.Parent.Name
FocusSubform = Application.Screen.PreviousControl.Name
FocusSubformControl = ?????
Similarly, my subform has its own nested subform and I would like to do the same with this
FocusForm = Application.Screen.PreviousControl.Parent.Name
FocusSubform = Application.Screen.PreviousControl.Name
FocusSubform2 = ?????
FocusSubform2Control = ?????
The in-built floating number pad on the tablets is very fiddly to use, hence my coding of this custom one, however if someone knows where I might find code for a customisable number pad that writes directly into whatever window is active, this would similarly be much appreciated!
If called from a subform,Screen.PreviousControlreturns the name of the mainforms subfom-control (as mainform needs to be active to get the subform control (nested in mainform) active), not the subform (but they can have same name, just change controls name and you won't get subforms name returned, but subforms control name!).
Now how to get previous control of the subform? By its.ActiveControlproperty, as form was active before, its active control must be the previous control. (if you want to get previous control, when you stay on the same subform, you need to store it in a module variable)
As there may be multiple subforms inside of subforms, we just loop while the control is a subform and set it to the next subform.ActiveControltill finished.
Why bother with names, if you can use references? This enables using multiple instances of a form.
Just store the reference to the control in Form_Activate and use it inMouseUp:
'On top of forms code module
Option Explicit
Private PreviousFormControl As Access.Control
Private Sub Form_Activate()
On Error Resume Next ' ignore error if no previous control availible
Set PreviousFormControl = Application.Screen.PreviousControl ' this stores the reference not the name!
If Err.Number <> 0 Then
'Handle error here, e.g. disable controls, show msg, ...
End If
On Error GoTo 0 'Reset error handler (not needed only to remind you not just to ignore all errors!
Do While TypeOf PreviousFormControl Is SubForm ' Loop till control is not subform
Set PreviousFormControl = PreviousFormControl.Form.ActiveControl ' if subform, previous control of it is its current ActiveControl
Loop
End Sub
Private Sub Toggle1_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
'Add a 1 to the currently selected control
PreviousFormControl.Text = PreviousFormControl.Text & "1" ' concat "1" to controls text, no need to handle empty text as it can only be an vbNullString(""), even if Null, then Null & "1" => "" & "1" => "1"
PreviousFormControl.SetFocus
End Sub
however if someone knows where I might find code for a customisable number pad that writes directly into whatever window is active
Of course you can use any Virtual Keyboard running on windows that fit your needs. But then you may have to handle things like bring keyboard to front on wanted position.
numpad emulator was the first open source app I found on quick search, but looks goods on short test. Of course there may be better solutions out there, just search and test.
I have a form with combo boxes (cmbPort#) to select up to 8 serial ports. I want to first clear the item list for each, populate them with currently available system ports, and then add the option "Off" to each list. Finally, to set each combo box according to defaults saved in string spName(). I created a GroupBox (gBox1) and dragged each cmbPort onto it but I'm not sure how to reference the controls on it. I'm using VB 2015.
Can you help with VB.NET code to use loops ("For Each" or similar) to do this more efficiently?
Private Sub frmProp_Load(sender As Object, e As EventArgs) Handles MyBase.Load
cmbPort1.Items.Clear()
...
cmbPort8.Items.Clear()
For Each sp As String In My.Computer.Ports.SerialPortNames
cmbPort1.Items.Add(sp)
...
cmbPort8.Items.Add(sp)
Next
cmbPort1.Items.Add("Off")
...
cmbPort8.Items.Add("Off")
cmbPort1.Text = spName(1)
...
cmbPort8.Text = spName(8)
End Sub
Loops are an incredibly useful tool to master. I pitched here some code so you can get the idea, but I was working out of IDE so you might have to apply some fixes to this code to make it work as you want it to.
The main idea is that you shouldn't have to write a line more than once. If you multiply the same operation on several lines of code, you create potential problems for the future. Loops and subs are really helpful to prevent this kind of issues.
Private Sub frmProp_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'This is for later
Dim cmbIndex As Integer = 1
'You basically do the same operations for every Combobox in your list, son only one loop needed
For Each cmbPort As ComboBox In {cmbPort1, cmbPort2, cmbPort3 [...] cmbPort8} 'this is a way to declare an array
'Clear
cmbPort.Items.Clear()
'Add SerialPortNames
For Each sp As String In My.Computer.Ports.SerialPortNames
cmbPort.Items.Add(sp)
Next
'Add "Off"
cmbPort.Items.Add("Off")
'This last one is a little bit trickier because you want to match numbers
'This is the place where you get errors when something doesn't go as planned
'If you need to keep it inside the loop here's a way to achieve that, but honestly I would't do that
'Instead I would suggest that you take this part out of the loop and do it manually
If spName(cmbIndex) IsNot Nothing Then cmbPort.Text = spName(cmbIndex)
cmbIndex += 1
Next
End Sub
You shouldn't consider efficiency into this equation, as this operation will not be called all the time, only on load. I mean: you should always do things in the best way you can, but optimization is sometimes the enemy of good, readable code.
I'm having a very strange problem in a VB application. I have a function written like this:
In the innermost condition, two statements are commented out here. These were found to have no effect on the strange behaviour. This is the minimal example I've found causing trouble.
(Note that the names of objects have been changed in this example.)
Private Sub MyForm_CellValidating(ByVal sender As Object, ByVal e As DataGridViewCellValidatingEventArgs) Handles myDGV.CellValidating
Dim dgv As DataGridView = CType(sender, DataGridView)
Select Case dgv.Columns(e.ColumnIndex).Name
Case "uniqueColumn"
' Validate that the values in our unique column are unique.
For i As Integer = 0 To dgv.RowCount - 1
If i <> e.RowIndex Then
' Here i != j, so compare to the value...
If e.FormattedValue = dgv.Rows(i).Cells(e.ColumnIndex).FormattedValue Then
e.Cancel = True
'dgv.ShowRowErrors = True
'dgv.Rows(e.RowIndex).ErrorText = "Data in the unique column must be unique"
End If
End If
Next 'i
Case Else
' Perform no validation.
End Select
End Sub
What trouble, you ask? For some inexplicable reason, whenever the line
e.Cancel = True
is executed, afterwards, nearly all buttons and form widgets in the entire application, including even the close button in its window bar (what a user would use to exit the application) stop doing whatever they previously did and now call this event handler instead.
In other words, commenting out that line (and doing the validation manually when the form is submitted) fixes the problems. I'd like to know why this happens, though. Some pointers:
Here's a list of which things are not affected:
The minimize and maximize button in the top bar.
All objects in its menu bar.
This handler is private to its form class, it's not referenced anywhere else in the application.
I'm at a loss. Just how? What could possibly cause this?
e.Cancel is for stopping the validation when the input is deemed incorrect. This causes the cell to still have focus as the user is expected to correct whatever they did wrong. The CellValidating event will then be raised again whenever the cell is about to lose focus until your code deems the input to be correct.
You can use the Control.CausesValidation property to control whether a control (for instance a button) should raise validation events when it gains focus.
I am creating a simple application that would enable me to input information into some textboxes and then, after pushing a button (called Addbtn) combine those into one string. This string would be added to a checkboxlist called ConcernsChk. When one or more of these strings are completed, the user would click the appropriate checkbox and click a button (called CompleteSortBtn) which would transfer that string to another checkboxlist. The issue I'm having is that my checkboxlist items do not delete according to their checked status. They delete one at a time beginning from the top and moving down.
Here's the code in question:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles CompleteSortBtn.Click
Dim Disposition As String = ""
Dim i As Integer
If ConcernsChk.CheckedItems.Count > 0 Then
For i = 0 To (ConcernsChk.Items.Count - 1)
If ConcernsChk.GetItemChecked(i) = True Then
Disposition = ConcernsChk.Items(i)
DispositionChk.Items.Add(Disposition)
ConcernsChk.Items.Remove(Disposition)
End If
Next
Else
MessageBox.Show("Please add Concerns before marking them complete.")
End If
I keep getting an error thrown that I cannot equal 3 and I have no idea what to do from here. This is thrown whether there are 2 items in the checkboxlist or 10.
Long story short, when I push the CompleteSortBtn, I want the program to do 4 things: 1. search through ConcernChk 2. Find checked boxes 3. Send the checked boxes to DispositionChk 4. Delete the checked items from ConcernChk
My apologies for the long post and thank you for whatever help you can give.
You are iterating though items not checkeditems.... count will be different.
SINCE you are removing items from the list you ALSO need to do it bottom to top.
For i = (ConcernsChk.Items.Count - 1) to 0 step - 1
If ConcernsChk.Items(i).Checked Then
Disposition = ConcernsChk.Items(i)
DispositionChk.Items.Add(Disposition)
ConcernsChk.Items.RemoveAt(I)
End If
Next
How can I set the FocusedItem property programatically?
I've tried this so far with no success:
If lvw.FocusedItem Is Nothing Then
If lvw.Items.Count > 0 Then
lvw.Focus()
lvw.HideSelection = False
lvw.Items(0).Selected = True
lvw.Items(0).Focused = True
lvw.FocusedItem = lvw.Items(0)
lvw.Select()
End If
End If
btw the form where the listview is has not called the ShowDialog method yet.
Can this be the reason for this not to work?
You have to understand that each control on the Form and the Form itself is a window and for the window to have focus it must first be created and assigned a handle.
For a basic description of this, I refer you to: All About Handles in Windows Forms The following excerpts are from the referenced article.
What is a Handle?
A handle (HWND) is the return value from CreateWindowEx which the Windows Operating System uses to identify a window. A "window" in win32 is a much broader concept than you may think - each individual button, combobox, listbox etc comprises a window. (For more information see About Window Classes ) NOTE: there are other things known as "Handles" in the Framework - e.g. GDI Handles from a Bitmap or Handles to Device Contexts (HDCs) - this article discusses HWNDs only.
...
When does a Control create its handle? (When does a control call CreateWindowEx?)
A control tries as much as possible to defer creating its handle. This is because setting properties forces chatty interop between the CLR and user32.
Typically the handles for all the controls are created before the
Form.Load event is called. Handles can also be created if the "Handle"
property is called and the handle has not yet been created, or
CreateControl() is called.
So a window's handle is not immediately created when you instantiate a control. However, you can force a control to create its handle by referencing its Handle property.
So if you first get the ListView to create its handle, then when you set those properties that you wanted.
Dim f2 As New Form2
' you do not need this condition, it is here only for demonstration purposes
' so that you can step through the code in the debugger and observe the
' code execution.
If Not f2.ListView1.IsHandleCreated Then
' retrieval of the Handle will cause a handle to be created
' if it has not yet been created
' if you delete the If-Then block, you will need to retain the
' following statement
Dim h As IntPtr = f2.ListView1.Handle
End If
f2.ListView1.FocusedItem = f2.ListView1.Items(2)
f2.ListView1.Items(2).Selected = True
f2.ListView1.Items(2).Focused = True
f2.ActiveControl = f2.ListView1
f2.ShowDialog()
As others have commented, your code should work as written. If all you need is to programmatically access the focused item in your code, you shouldn't be experiencing any difficulties. (If you are, please describe them.)
If you are looking for a visual effect (the row being highlighted), my guess is that your code is in another control's event and the focus is being set back to that control automatically the instant after your code runs. More than likely your code needs to be where it is and trying to move it elsewhere to prevent this issue would be a waste of time.
However, there are other ways to set a row apart visually. When a list view isn't likely to stay focused, my preferred method is to distinguish the selected item with a different fore/back color. (You can use the focused item if you prefer, but I find the selected item more useful. Your call.)
Here is an example which visually highlights the selected row, regardless of focus:
Private Sub lvw_SelectedIndexChanged(sender As Object, e As EventArgs) Handles lvw.SelectedIndexChanged
If lvw.Items Is Nothing Then Exit Sub
For Each lvi As ListViewItem In lvw.Items
If lvi.Selected = True Then
lvi.ForeColor = Color.DarkGray
lvi.BackColor = Color.LightCyan
Else
lvi.ForeColor = Color.Black
lvi.BackColor = Color.White
End If
Next
End Sub
EDIT:
In response to the added information that this form is being displayed using ShowDialog, yes, that is likely the source of your problem.
ShowDialog creates a new instance of the form. Therefore, if you have set any properties of a form or its controls, and later call ShowDialog to display that form, the form displayed is a new copy of the original form and will not reflect the changes you made programatically.
Imagine you sit down at a computer where a blank Word document is already open. You type something in it and then open a new document. The text you typed in the first document is not copied to the second. I think this is the root of your troubles here.