I want to display an image for 1 second and then disappear it. The code i'm trying to use is:
PictureBox4.Visible = True
System.Threading.Thread.Sleep(1000) ' 1 second delay
PictureBox4.Visible = False
But so far it's not working, is there a way to make this code works or any other methods to implement a delay in vb.net?
The reason why your code isn't working is because Sleep is tying up the UI thread and the control is never redrawn. So technically the Visible property is being changed, it is just that the user never sees the change.
You have a couple of options. One is to use a System.Timers.Timer (documentation) and set the AutoReset to false and the Interval to 1,000. Before you start the timer you would show the control and then in the Timer's Elapsed event you would hide the control. Here is a quick example:
Private ReadOnly _timer As Timers.Timer
Sub New()
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
_timer = New Timers.Timer() With {
.AutoReset = False,
.Interval = 1000,
.SynchronizingObject = Me
}
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
' create an event handler for the Elapsed event
AddHandler _timer.Elapsed, Sub() PictureBox4.Hide()
' show the control then start the timer
PictureBox4.Show()
_timer.Start()
End Sub
Update
Per JMcIlhinney's suggestion, I'm setting the SynchronizingObject property so that you don't have to call the Invoke method when hiding the control.
Try this
PictureBox4.Visible = True
Application.DoEvents()
System.Threading.Thread.Sleep(1000)
PictureBox4.Visible = False
Related
I'm new to Visual Basic and overall kind of new to coding in general.
Currently I work on a program which uses a filewatcher. But If I try this:
Public Class Form1
Private WithEvents fsw As IO.FileSystemWatcher
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
fsw = New IO.FileSystemWatcher("PATH")
fsw.EnableRaisingEvents = True
' fsw.Filter = "*.settings"
End Sub
Private Sub GetSettingsFromFile()
Some Code
More Code
CheckBox1.Checked = True
End Sub
Private Sub fsw_Changed(sender As Object, e As FileSystemEventArgs) Handles fsw.Changed
fsw.EnableRaisingEvents = False 'this is set because the file is changed many times in rapid succesion so I need to stop the Filewatcher from going of 200x (anyone has a better idea to do this?)
Threading.Thread.Sleep(100)
GetSettingsFromFile()
fsw.EnableRaisingEvents = True 'enabling it again
End Sub
End Class
But when I do this (trying to change anyhting in the form) I get this error:
System.InvalidOperationException (WinForms.IllegalCrossThreadCall)
It wont stop the program from working, but I want to understand what is wrong here and why the debugger is throwing this at me
regards
The event is being raised on a secondary thread. Any changes to the UI must be made on the UI thread. You need to marshal a method call to the UI thread and update the UI there. Lots of information around on how to do that. Here's an example:
Private Sub UpdateCheckBox1(checked As Boolean)
If CheckBox1.InvokeRequired Then
'We are on a secondary thread so marshal a method call to the UI thread.
CheckBox1.Invoke(New Action(Of Boolean)(AddressOf UpdateCheckBox1), checked)
Else
'We are on the UI thread so update the control.
CheckBox1.Checked = checked
End If
End Sub
Now you simply call that method wherever you are and whatever thread you're on. If you're already on the UI thread then the control will just be updated. If you're on a secondary thread then the method will invoke itself a second time, this time on the UI thread, and the control will be updated in that second invocation.
I'm trying to make a "rotator" on a form that cycles through a series of urls and displays the url in the WebBrowser control. The following code displays my form, but the form remains white/blank and then the last url in the array appears after a while. When I put a MessageBox in-between each url, to create a stop, it works and each url appears. I've tried putting a Sleep in place of the MessageBox, but that didn't work. I've also tried increasing the Sleep time, but that didn't work either. How can I make it work correctly?
Sub Rotate()
Dim Urls() As String = {"www.stackoverflow.com", "www.google.com", "www.yahoo.com"}
Dim counter As Integer = 0
Form3.Show()
Do Until counter = 3
Form3.WebBrowser1.ScriptErrorsSuppressed = True
Form3.WebBrowser1.Navigate(Urls(counter))
'MessageBox.Show("Next")
counter = counter + 1
System.Threading.Thread.Sleep(2000)
Loop
End Sub
You can call Application.DoEvents after changing the URL so that the control gets the chance to redraw itself.
However, a better approach would be to use a timer which fires every 2 seconds and then change the URL in the event handler so that your UI keeps responsive.
For example setup a new field myTimer in your form, init it in your form's loading event and in the Tick event you call your Rotate method. As Rotate is now called several times, we have to move the counter variable out of the method and make it a field so that we keep its value between the invocations. I usually write C# so hopefully I did not make some typos below :)
Private WithEvents myTimer As System.Windows.Forms.Timer
Private counter As Integer
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
' ... your existing code ...
counter = 0
myTimer = New System.Windows.Forms.Timer
myTimer.Interval = 2000
myTimer.Enabled = True
myTimer.Start()
End Sub
Private Sub myTimerTick() Handles myTimer.Tick
Rotate()
End Sub
Sub Rotate()
Dim Urls() As String = {"www.stackoverflow.com", "www.google.com", "www.yahoo.com"}
WebBrowser1.ScriptErrorsSuppressed = True
WebBrowser1.Navigate(Urls(counter))
counter = counter + 1
If counter > 3 Then myTimer.Stop()
End Sub
I want to specify in a text field how many timers I want to add to my form and specify the code that should be into the timer.
For instance: My textbox says "2" and then I click a button and it creates two timers and adds a specific source code for both timers.
I have tried different codes and while they worked, I wasn't able to specify the number of controls on a form to create.
How can I achieve this efficiently?
Thanks
Just to create one timer
Public Class Form1
private _timer as Windows.Forms.Timer
...
Public Sub New()
...
_timer = New Timer(Me)
_timer.Interval = 1000 'Timer will trigger one second after start
AddHandler _timer.tick, AddressOf Timer_tick 'Timer will call this sub when done
End Sub
Sub Button_click(sender as Object, e as EventArgs)
_timer.Start() 'Start the timer
...
End Sub
Private Sub Timer_tick(sender as Object, e as EventArgs)
MessageBox.Show("Timerrr!!")
End Sub
...
End Class
Now if you want to create more than one timer, you can use an array of Timer.
In this case, I used a form conatining a NumericUpDown controll element, a button and a label, plus two labels which only contain text.See this picture
To create the timers, I use the function add_timers(timercount), which looks like this:
Function add_timers(timercount As Integer)
'Using a loop to creat <timercount> timers
For g As Integer = 1 To timercount
'Creating new timer 't'
Dim t As New Timer()
'setting interval of t
t.Interval = 1000
'Enabling timer
t.Enabled = True
'Code which runs when t ticks
AddHandler t.Tick, AddressOf TimerTick
Next
End Function
This function gets called when Button1, the start button gets pressed. It uses NumericUpDown1.Value as the parameter for the function. The function uses a loop to create new timers t, sets their intervals and the code to run when they tick.
Unfourtunately, I didn't find a way to dynamically create code, so every timer performs the same action. Using arrays and loops in a clever way might enable you to use different value for each timer. To create code for the timer use a Sub:
Sub TimerTick(ByVal sender As Object, e As EventArgs)
'Add your code here
Label1.Text += 1
End Sub
The complete code I use is:
Public Class Form1
Function add_timers(timercount As Integer)
'Using a loop to creat <timercount> timers
For g As Integer = 1 To timercount
'Creating new timer 't'
Dim t As New Timer()
'setting interval of t
t.Interval = 1000
'Enabling timer
t.Enabled = True
'Code which runs when t ticks
AddHandler t.Tick, AddressOf TimerTick
Next
End Function
Sub TimerTick(ByVal sender As Object, e As EventArgs)
'Add your code here
Label1.Text += 1
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
add_timers(NumericUpDown1.Value)
End Sub
End Class
Packing the timers into an array is possible, that way you can easily access each timer with its index. Serach for it on the internet, and if you then have no idea of how to do it, tell me in the comments.
net program that uses excel as a datasource. I then fill a datagridview with this datasource and make changes to the dataset via the datagridview. I'm trying to find a way to refresh this dataset via a button that will update the values after a change. My only problem is that I'm trying to set up a timer in my refresh method but it never initializes/starts. I can't figure out why, from what I've found online the way to start a timer in vb.net is to set the timer variable to enabled = true. I've stepped into my debugger and found that the timer never starts. Here is my code below, if there is anyone who can figure out why this timer isn't starting I would greatly appreciate your help!
Dim mytimer As New System.Timers.Timer
Sub refresh()
write2Size()
mytimer.timer = New System.Timers.Timer(20000)
'Starting Timer
mytimer.Enabled = True
Cursor.Current = Cursors.WaitCursor
AddHandler mytimer.Elapsed, AddressOf OnTimedEvent
objworkbook.Save()
objExcel.ActiveWorkbook.Save()
myDS.Clear()
retrieveUpdate()
'Setting the cursor back to normal here
Cursor.Current = Cursors.Default
End Sub
Private Shared Sub OnTimedEvent(source As Object, e As ElapsedEventArgs)
Console.WriteLine("The Elapsed event was raised at {0}, e.SignalTime)
End Sub
You are creating a timer here
Dim mytimer As New System.Timers.Timer
but you only assign a handler to the one you create inside the Refresh routine.
Would have expected
Dim mytimer As New System.Timers.Timer(20000)
AddHandler mytimer.Elapsed, AddressOf OnTimedEvent
then
Private Shared Sub OnTimedEvent(source As Object, e As ElapsedEventArgs)
Console.WriteLine("The Elapsed event was raised at {0}, e.SignalTime)
Refresh()
End Sub
and something like
Sub refresh()
myTimer.Enabled = False
// refresh the doings
myTimer.Enabled = True
End sub
Excuse the lack of VBness, I'm a C# boy.
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