First off, I do not work with winform development full time so don't bash me too bad...
As the title somewhat depicts, I am having an issue refreshing the controls on a form after an event has been raised and captured.
On "Form1" I have a Dockpanel and am creating two new forms as shown below:
Public Sub New()
InitializeComponent()
dpGraph.DockLeftPortion = 225
dpGraph.BringToFront()
Dim frmT As frmGraphTools = New frmGraphTools()
Dim frmG As frmGraph = New frmGraph()
AddHandler frmT.UpdateGraph, AddressOf frmG.RefreshGraph
frmT.ShowHint = DockState.DockLeft
frmT.CloseButtonVisible = False
frmT.Show(dpGraph)
frmG.ShowHint = DockState.Document
frmG.CloseButtonVisible = False
frmG.Show(dpGraph)
End Sub
Within the frmGraphTools class I have the following delegate, event, and button click event defined:
Public Delegate Sub GraphValueChanged(ByVal datum As Date)
Public Event UpdateGraph As GraphValueChanged
Private Sub btnSaveMach_Click(sender As Object, e As EventArgs) Handles btnSaveMach.Click
RaiseEvent UpdateGraph(dtpJobDate.Value.ToString())
End Sub
Within the frmGraph class I have the following Sub defined:
Public Sub RefreshGraph(ByVal datum As Date)
CreateGraph(datum)
frmGraphBack.dpGraph.Refresh()
End Sub
I have a ZedGraph control on the frmGraph form that is supposed to be refreshed/redrawn upon the button click as defined on frmGraphTools. Everything seems to working, the RefreshGraph Sub within frmGraph is being executed and new data is pushed into the ZedGraph control however, the control never updates. What must be done to get the frmGraph form or the ZedGraph control to update/refresh/redraw properly?
Pass the reference to RefreshGroup method from the correct instance of frmGraph
AddHandler frmT.UpdateGraph, AddressOf frmG.RefreshGraph
also this call should be flagged by the compiler because you are passing a string instead of a Date
RaiseEvent UpdateGraph(dtpJobDate.Value.ToString())
probably you have Option Strict Off
Related
I would like to set the background color for a certain type of control on all child forms that open. I have an MdiParent form that is used to open the other forms within itself. I don't want to add code to each child form as this would be very extensive. This would be used as a theme feature for the application so I would like to have it automatically change the background colors based on logic in the main form. Is there something like a global event that could trigger for all Form.Load events?
So far I have created an event in the Parent form but it doesn't work for nested controls
Private Sub frmMain_MdiChildActivate(sender As Object, e As EventArgs) Handles Me.MdiChildActivate
Dim ParentControl As frmMain = sender
Dim ChildControl = ParentControl.ActiveControl
If ChildControl IsNot Nothing Then
For Each FormControl As Control In ChildControl.Controls
If FormControl.GetType = GetType(GroupBox) Then
RemoveHandler FormControl.Paint, AddressOf PaintBorderlessGroupbox
AddHandler FormControl.Paint, AddressOf PaintBorderlessGroupbox
End If
Next
End If
End Sub
I was able to accomplish this by using Form.MdiChildActivate and adding the event to the appropriate controls based on the Event and EventHandler.
Private Sub frmMain_MdiChildActivate(sender As Object, e As EventArgs) Handles Me.MdiChildActivate
Dim ParentForm As frmMain = sender
Dim ChildForm = ParentForm.ActiveMdiChild
Dim EventName = "Paint"
Dim EventHandlerName = "PaintBorderlessGroupBox"
If ChildForm IsNot Nothing Then
AddEventToControls(ChildForm, GetType(GroupBox), EventName, EventHandlerName)
End If
End Sub
Private Sub AddEventToControls(Control As Control, ControlType As Type, ControlEventName As String, ControlEventMethod As String)
For Each ChildControl In Control.Controls
If ChildControl.GetType = ControlType Then
If ChildControl.Controls.Count > 0 Then
AddEventToControls(ChildControl, ControlType, ControlEventName, ControlEventMethod)
End If
Dim EventMethod = Me.GetType().GetMethod(ControlEventMethod, BindingFlags.NonPublic Or BindingFlags.Instance)
Dim ControlEvent As EventInfo = ControlType.GetEvent(ControlEventName)
Dim del = [Delegate].CreateDelegate(ControlEvent.EventHandlerType, Me, EventMethod)
ControlEvent.RemoveEventHandler(ChildControl, del)
ControlEvent.AddEventHandler(ChildControl, del)
End If
Next
End Sub
The call to AddEventToControls() assigns the handler to the Control and any child controls that it would also apply to. In this case I am setting the Control.Paint event to paint a GroupBox a specific way. This may not be the cleanest method to accomplish this but I was able to create a "Global Event" for all child forms without ever touching the code on each form.
In your parent form, keep a collection of all Child Forms that have been activated. You can then traverse that collection and change the relevant control property for each one.
For Each ChildForm in MyCollection
ChildForm.TextBox.BackColor = Red
Next
Of course:
The ChildForm control has to be accessible by the parent form
The ChildForm has to still exist (i.e. not been closed in the mean
time)
You can't check for ChildForm closure because you are not adding any
code to the ChildForm to signal such an event.
You have to handle the exceptions when you try to change a form that
has been closed.
Much easier to include a method in your ChildForm design for ChangeColour(), whether that method is fired by event or direct call is your design decision. And to include a method to tell the parent form when a ChildForm dies so that it stops looking for it.
hello I have a problem to update a progress bar and a label inside a StatusStrip in the main form.
there are 2 controls in the form inside a StatusStrip:
Progressbar (ToolStripProgressBar)
ProgressLabel (ToolStripStatusLabel)
Basically I have this situation:
Public Class Main
Public Sub TEST(ByVal sender As Object, ByVal e As DoWorkEventArgs) Handles TEST.DoWork
Dim tmp as New NAMESPACE1.CLASS2(VALUES)
End Sub
End Class
Namespace NAMESPACE1
Public Class CLASS2
Public Sub New(VALUES)
Main.Progressbar.Value = 15
Main.ProgressLabel.Text = "hello!"
End Sub
End Class
End Namespace
The problem is that text or value of the controls are updated (I see it using breakpoints) in the code but not in the form in which progressbar is always a 0% and label always as nothing.
I think it's an update or refresh problem of the main form. i have tried to do Main.Refresh() and Main.Update() but it does not work anyway.
Thanks in advance.
You have 2 issues in play. The first is that Main is a class name, not a runtime reference or object variable. See Idle_Mind's answer for using Me to get the runtime object reference.
The second problem is that since Class2 is created in DoWork, it is created on the background thread, which will prevent it from accessing UI controls (which are created on the UI thread). You will get an illegal cross thread operation exception (even if you dont see it).
I'd suggest that Class2 does nothing useful which can't be done using the ReportProgress method. Getting rid of it also gets rid of the form reference issue since an event is raised on the same thread as the UI controls:
Private WithEvents bgw As BackgroundWorker
...
' in a button click or whatever starts the worker:
bgw = New BackgroundWorker
bgw.WorkerReportsProgress = True
bgw.RunWorkerAsync(5) ' times to loop
...
Private Sub bgw_DoWork(sender As Object,
e As DoWorkEventArgs) Handles bgw.DoWork
' NOTE
' This code executes on a different thread
' so do not reference UI controls!
' e.Argument is the value passed - amount of work
Dim max As Integer = CInt(e.Argument)
For n As Integer = 1 To max
Threading.Thread.Sleep(250) ' emulates work
' causes the ProgressChanged event to fire:
bgw.ReportProgress(n, String.Format("{0} of {1}", n.ToString, max.ToString))
Next
End Sub
Private Sub bgw_ProgressChanged(sender As Object,
e As ProgressChangedEventArgs) Handles bgw.ProgressChanged
'ProgressChanged fires on the UI thread, so it is safe to
' referenece controls here
TextBox4.Text = e.UserState.ToString
TextBox4.Refresh()
End Sub
Paste the code and you can see the message change in the TextBox. The same would work using your ProgressBar and ProgressLabel.
bgw.ReportProgress(n, arg)
The first argument will map to e.ProgressPercentage in the ProgressChanged event. The second is optional - UserState. I used it to pass a string for illustrative purposes (the form can already know the amount of work since it told the BGW what to do.)
If Class2 has some other purpose, you can use it as long as it is created on the UI thread (in the form) and used on that thread (ie in ProgressChanged event). You also need a method to talk to the controls so you dont have to create a new one each time:
Private myObj As Class2 ' declaration
...
myObj = New Class2(Me) ' instance with frm ref
In class2:
Public Sub Update(value As Integer, msg As String)
frmMain.Progressbar.Value = value
frmMain.ProgressLabel.Text = msg
End Sub
Then in the ProgressChanged event:
myObj.Update(x, y)
Where x and y are the value and message from whereever.
Here's an example of passing a reference to MAIN as suggested by Plutonix. I've intentionally left your pseudo-code style intact:
Public Class MAIN
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
TEST.RunWorkerAsync()
End Sub
Private Sub TEST_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles TEST.DoWork
Dim tmp As New NAMESPACE1.CLASS2(Me, VALUES) ' <-- Form reference being passed via 1st parameter
End Sub
End Class
Namespace NAMESPACE1
Public Class CLASS2
Private frmMain As MAIN
Public Sub New(ByVal frmMain As MAIN, VALUES)
Me.frmMain = frmMain
Me.frmMain.Progressbar.Value = 15
Me.frmMain.ProgressLabel.Text = "hello!"
End Sub
End Class
End Namespace
I am new in vb.net, I have a data collection application that use scan data in warehouse. it is window system, I couldn't get the event handling work. Please help me find what is wrong with my program below.
Here is the project, In the app I have a scanner class that I use it to scan barcode, and when scan happens raise an event to let the forms know. many forms can use scan data. But only the form visible on top will handle the scanned data.
I have 2 forms order form and ticket form, they both handle the scandata event. First order form handles scan data event and fill in the scanned order text field, then it automatically launches ticket form, and the ticket form suppose to handle the scan data event and post data on ticket form.
The Order form handles the event fine, the problem is after launching the ticket form automatically, it seems cannot associate to the event, the event seems still with the Order forms, So,ticket form not reveiving it and does nothing.
I have to use LaunchTickets() in order form to get to ticket due to business request, How do I implement this to get the event associate to correct form whatever the form visible on top in my application? I don't know if there is a way to get around, if not, what is the best way to implement this? please help me to get this work.
Public Class ClsComPort
Public Shared Event NewScanData(ByVal ScanData As String)
Public Function InitializebcrScanner() As Boolean
AddHandler mySerialPort.DataReceived, AddressOf mySerialPort_DataReceived
End Function
Private Sub mySerialPort_DataReceived(ByVal sender As Object, ByVal e As SerialDataReceivedEventArgs)
'omitted steps to get the scanned data
ScanData = str.Trim()
RaiseEvent NewScanData(scandata) 'raise the scan event
End sub end class
Public Class frmOrder
Friend WithEvents scanner As New ClsComPort
Private Sub GetScanData(ByVal ScanData As String) Handles scanner.NewScanData
txtOrder.Text = ScanData 'this runs ok, I got the scan data in this field
LaunchTickets() 'App automatically go to next form- ticket form, this seems to cause the event handling issue
End Sub
Private Sub LaunchTickets()
Me.Visible = False
frmTickets.WindowState = FormWindowState.Maximized
frmTickets.ShowDialog()
Me.Visible = True
End Sub
End Class
Public Class frmticket
Friend WithEvents scanner As New ClsComPort
Private Sub GetScanData(ByVal ScanData As String) Handles scanner.NewScanData
txtTicket.Text = ScanData
'not working, just nothing happen, and when back to order form, program crashed
End Sub
End Class
When you make the instance of the frmticket class you are subscribing to your custom event, but that event only fires when the DataReceived event fires and that is not wired up until you call InitializebcrScanner(you did not call it) - which should be a Sub not a Function since you do not return a boolean value or need to. Make an instance of the form not the default instance.
Private Sub LaunchTickets()
Me.Visible = False
Dim ticketsForm As New frmTickets
ticketsForm.WindowState = FormWindowState.Maximized
ticketsForm.ShowDialog()
Me.Visible = True
End Sub
This:
Public Function InitializebcrScanner() As Boolean
AddHandler mySerialPort.DataReceived, AddressOf mySerialPort_DataReceived
End Function
Should be in the constructor:
Sub New()
AddHandler mySerialPort.DataReceived, AddressOf mySerialPort_DataReceived
End Sub
On every DataGridView1_SelectionChanged event I need to run a Private Sub OnSelectionChanged() of the form that is loaded into Panel1 (see the image http://tinypic.com/r/2nu2wx/8).
Every form that can be loaded into Panel1 has the same Private Sub OnSelectionChanged() that initiates all the necessary calculations. For instance, I can load a form that calculates temperatures or I can load a form that calculates voltages. If different element is selected in the main form’s DataGridView1, either temperatures or voltages should be recalculated.
The problem is - there are many forms that can be loaded into Panel1, and I’m struggling to raise an event that would fire only once and would run the necessary Sub only in the loaded form.
Currently I’m using Shared Event:
'Main form (Form1).
Shared Event event_UpdateLoadedForm(ByVal frm_name As String)
'This is how I load forms into a panel (in this case frm_SCT).
Private Sub mnu_SCT_Click(sender As Object, e As EventArgs) Handles mnu_SCT.Click
frm_SCT.TopLevel = False
frm_SCT.Dock = DockStyle.Fill
Panel1.Controls.Add(frm_SCT)
frm_SCT.Show()
Var._loadedForm = frm_SCT.Name
RaiseEvent event_UpdateLoadedForm(Var._loadedForm)
End Sub
‘Form that is loaded into panel (Form2 or Form3 or Form4...).
Private WithEvents myEvent As New Form1
Private Sub OnEvent(ByVal frm_name As String) Handles myEvent.event_UpdateLoadedForm
‘Avoid executing code for the form that is not loaded.
If frm_name <> Me.Name Then Exit Sub
End Sub
This approach is working but I’m sure it can be done way better (I'd be thankful for any suggestions). I have tried to raise an event in the main form like this:
Public Event MyEvent As EventHandler
Protected Overridable Sub OnChange(e As EventArgs)
RaiseEvent MyEvent(Me, e)
End Sub
Private Sub DataGridView1_SelectionChanged(sender As Object, e As EventArgs) _
Handles DataGridView1.SelectionChanged
OnChange(EventArgs.Empty)
End Sub
but I don't know to subscribe to it in the loaded form.
Thank you.
Taking into account Hans Passant’s comments as well as code he posted in related thread I achieved what I wanted (see the code below).
Public Interface IOnEvent
Sub OnSelectionChange()
End Interface
Public Class Form1
' ???
Private myInterface As IOnEvent = Nothing
' Create and load form.
Private Sub DisplayForm(frm_Name As String)
' Exit if the form is already displayed.
If Panel1.Controls.Count > 0 AndAlso _
Panel1.Controls(0).GetType().Name = frm_Name Then Exit Sub
' Dispose previous form.
Do While Panel1.Controls.Count > 0
Panel1.Controls(0).Dispose()
Loop
' Create form by its full name.
Dim T As Type = Type.GetType("Namespace." & frm_Name)
Dim frm As Form = CType(Activator.CreateInstance(T), Form)
' Load form into the panel.
frm.TopLevel = False
frm.Visible = True
frm.Dock = DockStyle.Fill
Panel1.Controls.Add(frm)
' ???
myInterface = DirectCast(frm, IOnEvent)
End Sub
Private Sub DataGridView1_SelectionChanged(sender As Object, e As EventArgs) _
Handles DataGridView1.SelectionChanged
' Avoid error if the panel is empty.
If myInterface Is Nothing Then Return
' Run subroutine in the loaded form.
myInterface.OnSelectionChange()
End Sub
End Class
One last thing – it would be great if someone could take a quick look at the code (it works) and confirm that it is ok, especially the lines marked with “???” (I don’t understand them yet).
I have two forms, form 1 and form 2 (windows application). How can i access and check a checkbox in form 1 from form 2. Initially i tried calling the form name and then the control like form1.chkCanada.checked = true, it did not work. And then i added a property in form 1
Public Property abc As Boolean
Get
Return chkCanadianStmtInd.Checked
End Get
Set(value As Boolean)
chkCanadianStmtInd.Checked = value
End Set
End Property
and then in form 2
Dim frm As New frm1
frm.abc = True 'Checked
And it still doesnt work. Am i missing anything here?
Alternatively you can pass a handle of form1 to form2 constructor
Form1:
Public Class Form1
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
Dim _form2 As New Form2(Me)
_form2.Show()
End Sub
End Class
Form2:
Public Class Form2
Public Sub New(ByVal _form1 As Form1)
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
_form1.CheckBox1.Checked = True
End Sub
End Class
Consolidating comments here:
In order to access controls on a form that shows another form to the user you have two options, if no interaction is needed with the first form while the second form is active you can use showdialog and do all of your logic after the second form has closed, if you ned to maintain the ability to interact with the first form while the second is still open then you need to use custom events.
Showdialog:
The simpler of the two options is to switch your form.show() function calls to form.showdialog(). This effectively tells the first form that it should stop processing at the form.showdialog() line and wait for the child form to close before proceeding. Once the second form is closed the first form will pick up where it left off and that would be where any processing that relies on the values of the second form would take place.
Custom Events:
If you want to allow the user to interact with both the first and second forms at the same time then you will need to use custom events. In order to do this you will need three things. The custom event, a raiseevent call and an event handler.
So in your Form2 class you will need to declare the custom event. In this case since you are trying to check(or uncheck I assume) a box your custom event declaration will look like:
public event ChangeCheckedValue(byref state as boolean)
Now on your button click event you will need to raise the event to the handler on Form1:
RaiseEvent ChangeCheckedValue(booleanValue)
Now that those statements are in place you will need to changed your form2 object that is being shown by Form1. What I normally do is make Form2 a form wide variable on Form1 and declare it like:
private withevents frm as Form2
Once you have the frm variable in your Form1 class you can add a handler for the ChangeCheckedValue event:
protected sub HandleCheckChanged(byref bln as boolean) handles frm.ChangeCheckedValue
'Set the checked state of your checkbox.
End sub
Once you have all that set up you should see what you expect.