I have a typical combobox with drop down items. An item in the dropdown consists of a string with a code then a space, then the description of the code. I'm trying to get the text of the combo box to show just the code after the selection has been made, but there is a race condition in which my the text field is not being updated by the combobox until AFTER I change it. How do I force the combobox to update itself, so I can change the text afterwards.
With code_combo_box
AddHandler .SelectedIndexChanged, AddressOf update_desc
End With
Private Sub update_desc()
If code_combo_box.SelectedIndex >= 0 Then
Dim temp_string As String() = code_combo_box.SelectedItem.split(" ")
code_combo_box.Text = temp_string(0)
End If
End Sub
The combobox gets updated to the selected item after update_desc is called wiping out my change.
I figured out the answer which is to flag the event as handled when I enter the update_desc subroutine. So I needed to catch the events when entering the routine with
update_desc(sender as object, e as system.eventargs)
and then inside the routine simply use
e.handled = true
and the event would not continue to fire after leaving the routine and my changes would remain.
Related
In my Form I have various Textboxes that I write into with an in Form keyboard I created using Buttons. I have this code in Form.Load, which uses an event handler to determine which Textbox has the Focus:
For Each control As Control In Me.Controls
If control.GetType.Equals(GetType(TextBox)) Then
Dim textBox As TextBox = control
AddHandler textBox.Enter, Sub() FocussedTextbox = textBox
End If
Next
Then I use this on each button to write a specific character:
Private Sub btnQ_Click(sender As Object, e As EventArgs) Handles btnQ.Click
If btnQ.Text = "Q" Then
FocussedTextbox.Text += "Q"
ElseIf btnQ.Text = "q" Then
FocussedTextbox.Text += "q"
End If
End Sub
Up to that point I'm good and everything works as intended. The problem is I also have a DataGridView I want to write into but can't focus on it selected cells as I do on Textboxes.
I tried this:
For Each control As Control In Me.Controls
If control.GetType.Equals(GetType(TextBox)) Then
Dim textBox As TextBox = control
AddHandler textBox.Enter, Sub() FocussedTextbox = textBox
ElseIf control.GetType.Equals(GetType(DataGridViewCell)) Then
Dim DGVC As DataGridView = control
AddHandler DGVC.CellBeginEdit, Sub() FocussedTextbox = DGVC
End If
Next
But it just selects my last Textbox.
I declared the variable FocussedTextbox as Control so it's not specific to Textbox but any control.
Any help will be greatly appreciated.
To add text to the current ActiveControl using Buttons, these Button must not steal the focus from the ActiveControl (otherwise they become the ActiveControl).
This way, you can also avoid all those FocusedTextbox = textBox etc. and remove that code.
You just need Buttons that don't have the Selectable attribute set. You can use a Custom Control derived from Button and remove ControlStyles.Selectable in its constructor using the SetStyle method:
Public Class ButtonNoSel
Inherits Button
Public Sub New()
SetStyle(ControlStyles.Selectable, False)
End Sub
End Class
Replace your Buttons with this one (or, well, just set the Style if you're already using Custom Controls).
To replace the existing Buttons with this Custom Control:
Add a new class object to your Project, name it ButtonNoSel, copy all the code above inside the new class to replace the two lines of code you find there.
Build the Project. You can find the ButtonNoSel Control in your ToolBox now. Replace your Buttons with this one.
Or, open up the Form's Designer file and replace (CTRL+H) all System.Windows.Forms.Button() related to the Virtual KeyBoard with ButtonNoSel.
Remove the existing event handlers, these are not needed anymore.
Add the same Click event handler in the Constructor of the class that hosts those Buttons (a Form or whatever else you're using).
You can then remove all those event handlers, one for each control, that you have now; only one event handler is needed for all:
Public Sub New()
InitializeComponent()
For Each ctrl As Control In Me.Controls.OfType(Of ButtonNoSel)
AddHandler ctrl.Click, AddressOf KeyBoardButtons_Click
Next
End Sub
Of course, you also don't need to add event handlers to any other control, this is all that's required.
Now, you can filter the Control types you want your keyboard to work on, e.g., TextBoxBase Controls (TextBox and RichTextBox), DataGridView, NumericUpDown etc.
Or filter only special cases that need special treatment (e.g., MonthCalendar).
To add the char corresponding to the Button pressed, you can use SendKeys.Send(): it will insert the new char in the current insertion point, so you don't need any other code to store and reset the caret/cursor position as it happens if you set the Text property of a Control.
In this example, I'm checking whether the ActiveControl is a TextBoxBase Control, then just send the char that the clicked Button holds.
If it's a DataGridView, first send F2 to enter Edit Mode, then send the char.
You could also just send a char (so, no filter would be required), but in this case, you'll replace, not add to, the existing value of that Cell.
Private Sub KeyBoardButtons_Click(sender As Object, e As EventArgs)
Dim selectedButton = DirectCast(sender, Control)
Dim keysToSend = String.Empty
If TypeOf ActiveControl Is TextBoxBase Then
keysToSend = selectedButton.Text
ElseIf TypeOf ActiveControl Is DataGridView Then
Dim ctrl = DirectCast(ActiveControl, DataGridView)
If TypeOf ctrl.CurrentCell IsNot DataGridViewTextBoxCell Then Return
SendKeys.Send("{F2}")
keysToSend = selectedButton.Text
Else
' Whatever else
End If
If Not String.IsNullOrEmpty(keysToSend) Then
SendKeys.Send(keysToSend)
End If
End Sub
► Note that {F2} is sent just once: when the Cell enters Edit Mode, the ActiveControl is a DataGridViewTextBoxEditingControl, hence a TextBox Control, handled by the TextBoxBase filter.
This is how it works (using just the code posted here):
I'm not sure if it is possible, but I would like to know if a listbox can be updated by adding or removing text by typing that text into a textbox without using a button event or some type of click event. I've tried using the text_changed event but it inserts the text as I type so I am unable to type an entire string and then move that into a listbox as a whole string.
What I am trying to do is scan a magnetic ID card through a reader and have it insert the data from that card into a listbox and when I scan the same card again, it will remove the data. This is for an employee logging system.
Thanks.
With the following code, if you type a string in TextBox1 and hit Enter, we check to see if the string already exists in ListBox1. If so, the string is removed from the ListBox, otherwise it is added. Then TextBox1 is cleared.
Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles TextBox1.KeyPress
If e.KeyChar = vbCr Then
If ListBox1.Items.Contains(TextBox1.Text) Then
ListBox1.Items.Remove(TextBox1.Text)
Else
ListBox1.Items.Add(TextBox1.Text)
End If
TextBox1.Clear()
e.Handled = True
End If
End Sub
Ok I have a bit of a weird question here. I have a program similar to a currency converter (it performs a mathematical function in order to produce a value to go in another textbox). What I want it to be able to do is identify the last textbox that you edited (there are 4) and then update the rest based on what you have inputted, the user then must be able to change a different textbox to change all of them.
If anyone can get me started on how to do it or even some sample code that would be much appreciated, thanks!
Sorry if I'm not making sense, just have a look at the google currency converter and think that with two more editable boxes.
This might be what you want if I understand you correctly.
In the form class, you have a variable called lastTextBoxChangedName which keeps track of which text box was the last to be edited.
Next there is an event handler which will fire when any of the four TextBoxes are changed. This merely updates lastTextBoxChangedName.
When you have finihed editing a textbox, and tab to the next one or click on something that causes a TextBox to lose input focus, the next event handler executes. This looks at lastTextBoxChangedName to see which was the last edited TextBox and you can insert your update code to replace the comments in the Select Case block.
Public Class Form1
Dim lastTextBoxChangedName As String
Private Sub TextBox_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged, TextBox2.TextChanged, TextBox3.TextChanged, TextBox4.TextChanged
lastTextBoxChangedName = sender.name
End Sub
Private Sub TextBox1_LostFocus(sender As Object, e As EventArgs) Handles TextBox1.LostFocus, TextBox2.LostFocus, TextBox3.LostFocus, TextBox4.LostFocus
updateTextBoxes()
End Sub
Private Sub updateTextBoxes()
Select Case lastTextBoxChangedName
Case "TextBox1"
'do updates appropriate to textbox1 changed
Case "TextBox2"
'do updates appropriate to textbox2 changed
Case "TextBox3"
'do updates appropriate to textbox3 changed
Case "TextBox4"
'do updates appropriate to textbox4 changed
End Select
End Sub
End Class
However, if you already have separate event handlers for each TextBox, don't add that first event handler for TextBox_TextChanged, just add the line ..
lastTextBoxChangedName = sender.name
into each handler.
In load page event:
I read some data from DB and then add this data to Combo box then select an item as default and enable of combo box changes to false.
When I load this page, the item witch selected highlights with blue color.
How to remove this highlight?
You can modify its SelectionLength property, which gets or sets how many characters have been selected (highlighted).
Just set it to 0 after you have selected the default item and you should be good to go:
ComboBox1.SelectionLength = 0
EDIT:
In your case this code is executed before the Load event has finished. Due to this the form has not been rendered yet, which is why it is not working for you.
The simple fix is to add this in the form's Shown event too:
Private Sub Form1_Shown(sender As Object, e As System.EventArgs) Handles Me.Shown
ComboBox1.SelectionLength = 0
End Sub
If you don't want the caret to be in the beginning you can also add this line to set it to the end of the text:
ComboBox1.SelectionStart = ComboBox1.Text.Length
The proposed solution does not work in VB.NET 2016
The easiest way to do is to pass focus to another element like a label in the SelectedIndexChanged event
In my project, I have a few textbox inputs, and some combo boxes with maybe 2 indexed items on a form. There's a button I'm disabling on load if no input is supplied to both textbox inputs, and it works great even if I delete out any text. However, I'm having issues with forcing the combo box to behave in the same manner. This work however:
Private Sub cboPickShirts_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cboPickShirts.SelectedIndexChanged
InputCheck_3 = True
If cboPickShirts.SelectedIndex < 0 Then
InputCheck_3 = False
End If
If InputCheck_3 = False Then
btnInputResult.Enabled = False
ElseIf InputCheck_3 = True Then
btnInputResult.Enabled = True
End If
End Sub
I have InputCheck_3 set up as a global variable in a Public Module. On form load, I'm disabling my button and it doesn't enable until I select one of the indexed items. My struggle to get the button disable again if any combo box text is entered and deleted out, leaving it null or empty. Any thoughts on what I'm missing or what I can add to get results? I guess I need a variable or event to notice the change (entering & deletion of text).
The problem you are having is that your SelectedIndexChanged event is not being triggered when you remove the selected item from your ComboBox. I would use the TextChanged event of your TextBox's and ComboBox and give it a common handler and check it that way. Something like this
Private Sub TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged, TextBox2.TextChanged, cboPickShirts.TextChanged
EnableCheck()
End Sub
Private Sub EnableCheck()
btnInputResult.Enabled = (String.IsNullOrEmpty(TextBox1.Text) And String.IsNullOrEmpty(TextBox2.Text) And ComboBox1.SelectedIndex = -1)
End Sub
You can also check that the comboBox is NullorEmpty the same way as the textbox's. As it stands right now the combobox will be enabled when the text no longer matches a selection.
One line code
btnInputResult.Enabled = If((cboPickShirts.SelectedIndex<0),False, True)