I wrote a program to controle the audio volume by a remote control.
It needs to keep focused, otherwise it does not receive its commands anymore.
In order to get the focus back a used a timer, checking every second if the form still has the focus.
Here is the code:
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
If Not Me.Focused Then
Me.Activate()
End If
End Sub
As long as I run it from within Visual Studio this works perfect.
When I close Visual Studio it does not take the focus back anymore.
I ran the program on another computer on which was no Visual Studio installed and it works!
What could be the problem?
Related
Hi everyone I need some help,
I am having a weird situation every time I try to call a window form I get this error
BC30469 Reference to a non-shared member requires an object reference.
I was originally working on Visual Studio 2010 when the first time contouring this problem so I thought that I may accidentally deleted or edited some code in the declaration of the form witch caused the problem so I closed the solution and created a new one to make sure that the problem is limited the solution not to VS. then I add window form "Form2" then created/added a button1 on Form1 to call Form2.Show()
simple code that should work fine but when I tape Form2.Show() it give that ERROR and red mark Form2
so I uninstalled VS2010 then Reset Windows 10 with option to wipe out all data on windows partition (I now that was extreme but I suspected that maybe the system was infected with some virus "prior action") so after that I checked the system with HitmanPro and found nothing then I installed VS2019 Community and get The some problem I searched on the web but did not found any similar case so here I am hoping that someone will resolve the mystery.
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Form2.Show()
End Sub
End Class
Form2 is empty form I didn't make any change on it
Before this problem showing up everything work fine now even old project have the same issue
Thanks
Edit: Add project as simple
https://mega.nz/file/FgoXkCwA#ootxYrXGnR6sQR_Pifjvz617-r_Az1ozXWB49oGxqKU
the project dose not contain any executable file
I usually do something like this when calling a subform:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
' using a Using block:
Using form2 as New Form2
form2.ShowDialog(Me)
form2.Close()
End Using
' using a With block
With New Form2
.ShowDialog(Me)
.Close()
End With
End Sub
ShowDialog(Me) keeps the subform open until a DialogResult is provided by the user (OK or Cancel usually).
The problem is happening on 2 of the company's computers and on a client computer, but we can not identify a pattern.
I was able to reproduce the error using a simple program that only opens an OpenFileDialog. The program must be run by the generated executable itself (NOT by Debug) and it is still running in the background even after closing. Below is the code of the program, along with a link to download the project and a video demonstrating the error.
Code:
Public Class Form1
Private ofdAbrir As Windows.Forms.OpenFileDialog
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
ofdAbrir = New Windows.Forms.OpenFileDialog
ofdAbrir.ShowDialog()
ofdAbrir.Dispose()
ofdAbrir = Nothing
End Sub
End Class
As you can see in the code above, I only have one form, so it is not the case that some form remains open and it is also not related to threads running since none is created.
To reproduce the problem, click on Button1, cancel the OpenFileDialog and try to close the form (clicking on X). The form apparently will close, but you will see at task manager that it still running. The big mystery is that this problem does not happens in all computers.
Video: https://drive.google.com/open?id=1sfdVUGQlwYNCQkl1Ht-cJSOb4433sqnT
Project: https://drive.google.com/open?id=1d4oJYUjaaZ9xnRj4CX3HXOQPqwMZmE0V
I couldn't reproduce the problem, but how about using this method:
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Using ofdAbrir As New Windows.Forms.OpenFileDialog
ofdAbrir.ShowDialog()
MsgBox(ofdAbrir.FileName)
End Using
End Sub
I've seen the video u posted...It is not your application that is running rather it is the vsHost.exe that is running :)...The problem shouldn't occur if u run the app outside visual studio.
If the problem is still there,just disable Enable Diagnostic Tools while debugging from Tools > Options > Debugging > Uncheck Enable Diagnostic Tools while debugging
Also u can disable Visual Studio hosting service from Project > Project Properties > Uncheck Enable the Visual Studio hosting service
I've come across a peculiar focusing issue. I have created the following "search" program:
It runs in the background.
When you double-tap the Ctrl key it becomes visible.
You can type in the textbox because the form has focus.
If the form loses focus (I click on my desktop, for example), it disappears after 3 seconds.
I double-tap the Ctrl key again, and again it becomes visible.
But this time, no matter what I try, the form is not focused and I cannot type in the textbox without first manually clicking on the form.
What's particularly interesting is that when I run this program in debug mode from Visual Studios, the program regains focus upon double-tapping Ctrl key and becoming visible, and I can immediately start typing in the text box. However, when I build this program and run it alone, the program appears but does not regain focus upon double-tapping Ctrl key, and therefore I cannot type in the text box until I manually click the form.
After Me.Show() I have tried:
Me.Focus()
Me.Validate()
Me.Select()
Textbox1.Select()
Textbox1.Focus()
The form is topmost and normally running in administrator, but the same problem arises regardless.
The issue can be recreated in a more simple manner. Create a form with
Button ("Button1")
TextBox
Two timers ("hideForm", "showForm") both with intervals of 1000
Code:
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
hideForm.Start()
sender.Enabled = False
End Sub
Private Sub hideForm_Tick(sender As Object, e As EventArgs) Handles hideForm.Tick
Me.Hide()
hideForm.Stop()
showForm.Start()
End Sub
Private Sub showForm_Tick(sender As Object, e As EventArgs) Handles showForm.Tick
showForm.Stop()
Me.Show()
Me.Activate()
End Sub
End Class
Click the button, and immediately click on a different window (so the form loses focus). Wait until the form is hidden and shown again. The textbox should have focus. Try typing.
If the program is run in debugging mode in Visual Studios, it works as expected. If you build the program and run it outside of VS, the form will reappear without focus, and you cannot type in the textbox without manually selecting the form.
Sorry for the long-winded explanation. It's a difficult issue to properly describe.
Try the form event handler Activate. Inside that method, you can use setFocus to gain focus for that particular Text Box. I know this answer is too late. But hope this helps someone.
Private Sub Form_Activate()
TextBox1.SetFocus
End Sub
Try an event handler for Form_Activate, and within that handler pass the focus to your textbox.
Instead of Focus, you can also try TextBox1.Select. This SO link provides some additional information and something about the difference between Focus and Select.
Select the Textbox you want to assign a focus to in the Design View Window.
Under the Properties window, set the TabIndex to 0 (zero).
I didn't even have to use the TextBox1.Focus() command. It still bothers me that the TabIndex overrides the Focus command.
What I tried (and worked for me), was to set the Focus() of the Textbox in the event handler Shown() [VB]:
Private Sub Form1_Shown(sender As Object, e As EventArgs) Handles MyBase.Shown
Me.Textbox1.Focus()
End Sub
Note: the Select() method just didn't do the job. I hope this helps anyone else that comes with this same issue.
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
MsgBox("test")
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
BackgroundWorker1.RunWorkerAsync()
End Sub
Once I click the Button1 ,Messagebox appears.When click okay with "Return" (enter) key it appears again and again...But when I click Return key permanently,almost 5 seconds later programs gives me the run time error.
Error is not English in my computer and I translated it.It is nearly mean "BackgroundWorker is busy,can't do two procces in the same time..."
I know that error.It is because of trying to run BackgroundWorker while it is running.In the code it just start with RunWorkerCompleted event.So it can't start again if "Work is not Completed".Who runs the BackgroundWorker ?
You need to read this post first, it talks about the dangers of re-entrancy and how dialogs (like MsgBox) solve the problem.
Which is what it is not doing in your program. A dialog can only be modal against other windows that are created on the same thread. That worker thread doesn't have any. So there is nothing that stops your Enter key press from also being seen by the control that has the focus. Button1. Note how you can simply use the mouse to select your main window and click the button. Kaboom.
That doesn't go wrong often enough as-is, you can help by leaning on the Enter key so it starts repeating. It will usually be detected by the message box window. But not always, there's a split second between DoWork ending and it starting back up. Just enough to give the UI thread a chance to see the keystroke. Now that Enter keypress operates Button1 and it starts the BGW back up again. So does the RunWorkerCompleted event handler, it cannot be started twice. Kaboom.
That's not the only problem with that dialog, you haven't discovered the other failure mode yet. A dialog needs an owner window, one that it can be displayed on top of. That message box does have one, it has to fallback to the desktop window. Now it is crapshoot which window is going to be in front. Could be the dialog, could be your main window. With the message box underneath your main window. The user cannot see it, has no idea that there is one. No taskbar button either.
Long story short: this cannot work. Only display UI on the UI thread. Only use a worker thread to do non-UI related work.
I have the vlc AxVLCPlugin21 control inside of a visual basic 2010 form and I have set it with the
ability to recognize to pause the video or music whenever I tap the space key.
The code below works and pauses the media when the windows form is showing and the vlc control is
not full screen. However when I make the vlc full screen and tap the space bar the media no longer
pauses. I think the full screen mode causes the windows form keydown event to be blocked.
I am not sure what I could try to fix this. I know the windows form has a previevkeydown event listed below
and the vlc control itself has its own previewkeydown event. But not sure what I might try to get the pause
to work when the space bar is pressed while in full screen mode. Any ideas appreciated. I have often had
problems getting keypresses to work with programs in VB. Is it because different controls seize control depending
on various settings?
I also use a Me.KeyPreview = True in the form load which supposedly forces the windows form to take precedence over taking keystrokes.
One other idea I tried but did not work was using e.Handled = True in the
keydown event which supposedly makes the form take all keyboard events and
will not allow other controls to receive them. Did not work in full screen.
Private Sub Form1_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles MyBase.KeyDown
If e.KeyValue = Keys.Space Then
AxVLCPlugin21.playlist.togglePause()
End If
End Sub
Private Sub Form1_PreviewKeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PreviewKeyDownEventArgs) Handles MyBase.PreviewKeyDown
End Sub
Private Sub AxVLCPlugin21_PreviewKeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PreviewKeyDownEventArgs) Handles AxVLCPlugin21.PreviewKeyDown
End Sub