I have to create a Loading form, while processing a calculus. This form should prevent any action to the other forms while performing this calculus so the most proper command to use should be ShowDialog(). I've also found that I need to run this command, in order to prevent the form freezing, with a BackgroundWorker. So what I've done is to define the button - that will start the calculus - and the BackgroundWorker itself. So this is what I wrote:
Private Sub Button4_Click(sender As Object, e As EventArgs) Handles Button4.Click
Form18.ProgressBar1.Minimum = 0
Form18.ProgressBar1.Value = 0
Form18.ShowDialog()
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
[calculus code and progressbar progression]
If Form18.ProgressBar1.Value = Form18.ProgressBar1.Maximum Then
Form18.Close()
hrrnativexcel.Visible = True
End If
End Sub
Even if I'm using the BackgroundWorker, when I press the button, the loading form - declared in my code as Form18 - becomes blocked and progressbar gets stuck at 0% loading. Could anyone tell me where I am doing wrong? I've tried to find something about BackgroundWorker with ShowDialog command but I haven't found anything that could help me. Thanks in advance.
Related
I am working in Visual Studio 2019 and writing in Visual Basic. I get this error: Cross-thread operation not valid: Control 'lblTesting' accessed from a thread other than the thread it was created on.' (lblTesting is just a label for testing purposes).
I call the FrmContacts like this:
Private Sub ContactsToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles ContactsToolStripMenuItem.Click
Me.Enabled = False
FrmContacts.Show()
End Sub
and return from the form like this:
Private Sub FrmContacts_Closed(sender As Object, e As EventArgs) Handles Me.Closed
Me.Close()
FrmMain.Enabled = True
End Sub
The error pops up when I exit FrmContacts.
I tried deleting the form and recreating it but the error is there as soon as I add any control. I am dumbfounded. Searching has not revealed any hints.
I had to take out the Me.Close() because I was closing a closed form. The new code works fine. It is:
Private Sub FrmContacts_Closed(sender As Object, e As EventArgs) Handles Me.Closed
FrmMain.Enabled = True
End Sub
Also, if your intention is to make the "main" form inaccessible until the "child" form is closed, then simply use ShowDialog() instead:
You can use this method to display a modal dialog box in your
application. When this method is called, the code following it is not
executed until after the dialog box is closed.
Private Sub ContactsToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles ContactsToolStripMenuItem.Click
FrmContacts.ShowDialog()
End Sub
So i have a tray icon that should behave the same way between 3 forms. I then created this code:
Private Sub TrayForm_MouseClick(sender As Object, e As MouseEventArgs) Handles NotifyIcon1.MouseClick
If e.Button = MouseButtons.Right Then
If Not Application.OpenForms().OfType(Of TrayForm).Any = 1 Then
TrayForm.ContextMenuStrip1.Show(Cursor.Position)
End If
End If
End Sub
Which is used to handle the tray icon. How can i do to share this event between the forms so i don't have to place this same code on every form?
How are event handlers working exactly? I looked online and on MSDN and it is not clear to me.
Thanks
Are you sure that you want to share the event, and not juste the code that will handle the event?
If you don't want to copy and paste your code, which you need to handle the events of more than one form, here's a way to do it:
Declare the sub which contains the code needed to handle the event as a public shared sub. Like this:
Public Shared Sub TrayForm_MouseClick(sender As Object, e As MouseEventArgs)
So, now you have a Sub which can handle the event you want to handle from all three forms.
Now, when you initialize those forms, add a line to make the shared Sub handle the event you want it to handle:
AddHandler NotifyIcon1.MouseClick, AddressOf ProjectName.FileName.TrayForm_MouseClick
ProjectName.FileName is meant here to be the path to refer to the shares Sub inside the file where you put it. I usually name it like ProjectNameUtils.vb or something like that.
If you just want to avoid copy and pasting your Sub so you don't have to modify it at several places every time you change something, this could be a way to achieve that.
As Stipulated by Hans Passant:
Sub Eclass_EventHandler(sender As Object, e As MouseEventArgs) Handles Me.MouseClick
If e.Button = MouseButtons.Right Then
If Not Application.OpenForms().OfType(Of TrayForm).Any = 1 Then
Me.ContextMenuStrip1.Show(Cursor.Position)
End If
End If
End Sub
On the Trayform.VB just did the trick.
But about the shared event. i Have one that would have to be:
Private Sub FormClosingEVENT(sender As System.Object, e As System.Windows.Forms.FormClosingEventArgs) Handles MyBase.FormClosing
If Not FromMenu Then e.Cancel = True
Me.WindowState = FormWindowState.Minimized
'Application.Exit()
End Sub
How should i handle this?
I am currently working on a project and decided to create a user interface for it using visual studio with a windows forms application(Visual Basic).
The problem I'm facing is that the user interface doesn't respond as quickly and smoothly as I'd like it to.
Mainly, I am using pictures as buttons to make the user form look more modern.
However, when I hover my mouse over a "button" it takes a while until the "highlighted button" appears.
P1 is the picture of the "normal button" and P2 is the picture of the "highlighted button".
Here is the short code I have for now:
Public Class Main
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
End Sub
Private Sub PictureBox1_MouseHover(sender As Object, e As EventArgs) Handles P1.MouseHover
P1.Visible = False
P2.Visible = True
End Sub
Private Sub P2_MouseClick(sender As Object, e As MouseEventArgs) Handles P2.MouseClick
'Call cmdInit()
'Call cmdConnectRobot()
'Call cmdUnlock()
End Sub
Private Sub Main_MouseHover(sender As Object, e As EventArgs) Handles Me.MouseHover
If P2.Visible = True Then
P2.Visible = False
P1.Visible = True
End If
End Sub
Private Sub P4_Click(sender As Object, e As EventArgs) Handles P4.Click
End Sub
End Class
Another problem I'm facing is that when I call other subs, the user form becomes unresponsive while the sub is running.
I researched and found that I could implement multi threading or async tasks but I'm a bit lost and would be extremely grateful if someone could guide me or point me in the right direction.
Thanks in advance!!
In this case your UI is responsive, however the MouseHover event is only raised once the mouse cursor has hovered over the control for a certain amount of time (default is 400 ms), which is what is causing the delay.
What you are looking for is the MouseEnter event, which is raised as soon as the cursor enters ("touches") the control:
Private Sub P1_MouseEnter(sender As Object, e As EventArgs) Handles P1.MouseEnter
P1.Visible = False
P2.Visible = True
End Sub
You can then use that together with the MouseLeave event on the second picture box to switch back to the non-highlighted image:
Private Sub P2_MouseLeave(sender As Object, e As EventArgs) Handles P2.MouseLeave
P1.Visible = True
P2.Visible = False
End Sub
However switching picture boxes like this is not optimal. I recommend you to look into how you can use Application Resources, then modify your code to only switch the image that one picture box displays.
Here are the basic steps:
Right-click your project in the Solution Explorer and press Properties.
Select the Resources tab.
To add an image either:
a. Drag and drop the image onto the resource pane.
b. Click the arrow next to the Add Resource... button and press Add Existing File....
Now, in your code add this right below Public Class Form1:
Dim ButtonNormal As Image = My.Resources.<first image name>
Dim ButtonHighlighted As Image = My.Resources.<second image name>
Replace <first image name> and <second image name> with the names of your button images.
Now you only need one picture box for the button:
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
P1.Image = ButtonNormal
End Sub
Private Sub P1_MouseEnter(sender As System.Object, e As System.EventArgs) Handles P1.MouseEnter
P1.Image = ButtonHighlighted
End Sub
Private Sub P1_MouseLeave(sender As System.Object, e As System.EventArgs) Handles P1.MouseLeave
P1.Image = ButtonNormal
End Sub
I'll start by saying i'm not a programmer by trade, and i'm sure someone will point out better ways of doing these things, but in regards to the threading question it's fairly simple to implement.
Imports System.Threading
Public Class Form1
Dim WorkerThread As New Thread(AddressOf DoWork)
'WorkerThread' can be any name you like, and 'DoWork' is the name of the sub you want to run in the new thread, and is launched by calling:
WorkerThread.start()
However there is a catch, the new thread is not able to interact directly with the GUI, so you cannot change textbox text etc... I find the easiest way to get changes made to the GUI is to drag a timer onto your form, and have the new thread change variables (pre-defined just below Public Class Form1), then use the Timer1 Tick event to monitor the variables and update the GUI if there are any changes.
I'm working with visual basic express 2010 to create a very simple application.
I know this is basic stuff but i need to know how to repeat the same function every X minute while the application is being left open.
This is all my code:
Public Class Form1
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
My.Computer.Network.DownloadFile(
"http://google.co.uk/images/someimage.png", "C:/Documents and Settings/All Users/Desktop/someimage.png")
End Sub
End Class
could someone please advise on this issue?
EDIT:
This is my entire code now:
Public Class Form1
Private Sub Timer1_Tick(sender As System.Object, e As System.EventArgs) Handles Timer1.Tick
My.Computer.Network.DownloadFile(
"http://new.tse.ir/en/json/MarketWatch/enMarketWatch_1.xls", "C:/temp/enMarketWatch_1.xls", "", "", False, 60, True)
End Sub
End Class
in the properties panel of the timer, I set the Enabled to true and Interval to 60000.
when i run this code, I get file downloaded but 1 second later, the file gets deleted automatically and an error pops up in the visual basic saying the operation has timed out
I tried to change the directory and still happening.
any advise would be appreciated.
Add a timer to your form in the graphical designer.
Double click the timer to generate its tick event handler code in the code window.
Move the code you want to repeat into a sub
Private Sub DownloadFile()
My.Computer.Network.DownloadFile("http://google.co.uk/images/someimage.png", "C:/Documents and Settings/All Users/Desktop/someimage.png")
End Sub
Add the command below into your timer tick event handler
DownloadFile()
Change your form.load event to
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
DownloadFile()
Timer1.Interval = x ' where x is the number of minutes*60000 because there are 60000 ticks in a minute
Timer1.Enabled = True
End Sub
The reason I've put your code into a separate sub is so that it is easily reusable in both the form.load handler and the timer.tick handler without having to write it again, and if in the future you need to change, for example the file path, you only need to remember to change it once.
Also I should add that, in the form.load handler I have included the DownloadFile method because, when the timer is enabled, it won't generate a tick until the interval has elapsed. Not at the beginning when the timer is enabled.
Also - as Plutonix suggested in comments below - If it is possible that the file to be downloaded will take longer to download than the length of the timer interval you should disable the timer in the DownloadFile sub and enable it again at the end of the sub. Like so :-
Private Sub DownloadFile()
Timer1.Enabled = False
My.Computer.Network.DownloadFile("http://google.co.uk/images/someimage.png", "C:/Documents and Settings/All Users/Desktop/someimage.png")
Timer1.Enabled = True
End Sub
i want to add a loading animation while the form is loading..i tried backgroundworker but i can't get it to work..plz help me out..
Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
CharTz.Show()
End Sub
Private Sub BackgroundWorker1_ProgressChanged(sender As Object, e As System.ComponentModel.ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
loadingscreen.show()
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
loadingscreen.close()
End Sub
All of the UI stuff must be done on the UI thread. It doesn't make sense to show a form from the background worker. Showing the form is a UI thing, so that needs to be done on the main UI thread. I'm quite certain that it's not true that the "takes about 3-4 seconds to show". It may very well take 3-4 seconds to do something, but it's not the showing-the-form part that's taking that long. That form must be doing something when it loads which is slowing it down. That's the stuff that ought to be put in a background worker thread. If all that slow logic is done in a background thread, then the form will show very quickly and it can then display some sort of animation until the background thread is done doing the work.