When I use System.Windows.Forms.Timer class and finish using it then I can't disable it.. it ticks even if I set its property Enabled to false. What is wrong with the code? here is an example:
int counter = 0;
private void timer1_Tick(object sender, EventArgs e) {
MessageBox.Show("Hello");
counter++;
if (counter == 10){
timer1.Enabled = false;
}
}
This is a subtle bug that's induced by the MessageBox.Show() call. MessageBox pumps a message loop to keep the UI alive. Which allows the Tick event handler to run again, even though it is already active from the previous tick. The counter variable doesn't get incremented until you click the OK button. As a result, the screen fills with message boxes and that won't stop until you click the OK button ten times.
You need to increment the counter before showing the message box. Fix:
int counter = 0;
private void timer1_Tick(object sender, EventArgs e) {
counter++;
if (counter > 10) timer1.Enabled = false;
else MessageBox.Show("Hello");
}
This kind of problem is also the reason that DoEvents() got such a bad reputation. It is pretty difficult to write code that can properly deal with the re-entrancy induced by the message loop. You need to keep boolean flags around that indicate that code is already active. Which is another way to solve your problem:
int counter = 0;
bool showingBox = false;
private void timer1_Tick(object sender, EventArgs e) {
if (showingBox) return;
showingBox = true;
try {
MessageBox.Show("Hello");
counter++;
if (counter == 10) timer1.Enabled = false;
}
finally {
showingBox = false;
}
}
You now get only one message box at a time, probably what you are really looking for.
I should mention that this re-entrancy problem is pretty specific to timers. A dialog takes counter-measures to avoid re-entrancy problems, it disables all the windows in the application. That ensures that the user cannot do things like closing the main window or clicking a button that brings up the dialog again. Both rather disastrous mishaps. That takes care of most of the 'unexpected' Windows notifications, basically any of the messages that are generated by the user. The edge case is a timer (WM_TIMER is not disabled) whose event handler has a UI effect.
It is because the MessageBox.Show blocks until the user presses OK.
The code below the MessageBox will not execute until after 10 OK buttons are pressed.
But the timer continues to fire even if the execution is blocked.
Try this code
int counter = 0;
private void timer1_Tick(object sender, EventArgs e) {
counter++;
if (counter == 10){
timer1.Enabled = false;
}
MessageBox.Show("Hello");
}
(just moved the MessageBox)
What about timer1.Stop()? I am not too familiar with this class, but looked it up quickly: Timer Class
try this:
int counter = 0;
private void timer1_Tick(object sender, EventArgs e) {
MessageBox.Show("Hello");
counter++;
if (counter == 10){
timer1.Stop();
timer1.Dispose();
timer1 = null;
}
}
It is also working for me. I placed the timer in the form, on the button click, I am calling timer1.start() and I put the following code in the tick event and its working.
int i = 0;
private void timer1_Tick(object sender, EventArgs e)
{
i++;
this.Text = i.ToString();
if (i == 10)
{
timer1.Enabled = false;
}
}
You need to call Stop.
int i = 0;
private void timer1_Tick(object sender, EventArgs e)
{
i++;
if (i == 10)
{
timer1.Stop();
}
}
I'm pretty sure the MessageBox is the culprit here. Maybe if you use a short execution interval for the timer handler then this could potentially cause your code to function undesirably, if executions are overlapping.
The problem would be, in this case, that the handler executes and displays the MessageBox which in turn halts execution of the current scope until the the prompt is acknowledged by the user, meanwhile the handler has started again, showing another prompt, and another, and so on. At this point, we have multiple MessageBoxes waiting for input, yet counter hasn't even been incremented once. When we click 'OK' on the prompt, counter increments as desired, but at this point has a value of 1, rather than a value representing the number of prompts shown. This means yet another prompt will be displayed if more time elapses, until the user clicks 'OK' on at least 10 prompts.
You could try inhibiting execution if the process is already under way in order to prevent concurrent runs:
private readonly ReaderWriterLockSlim Locker = new ReaderWriterLockSlim();
int counter = 0;
private void timer1_Tick(object sender, EventArgs e)
{
if (Locker.TryEnterWriteLock(0))
{
try
{
MessageBox.Show("Hello");
Counter++;
if (Counter == 10)
{
Timer.Enabled = false;
}
}
catch { }
finally
{
Locker.ExitWriteLock();
}
}
}
Related
so I have a problem where I want to make a label pop up when timer is enabled. I tried writing this but it just doesn't work. I have set every object property as needed, but still there is some kind of problem. Can you help me please? Thanks.
private void timer1_Tick(object sender, EventArgs e)
{
if (button3Click == true && FullNameBOX.Text == "")
{
timer1.Start();
while(timer1.Enabled == true)
{
label5.Show();
}
timer1.Stop();
}
else if(timer1.Enabled == false)
{
label5.Hide();
}
else
{
}
timer1_Tick is only executed once the timer is started and the timer interval is elapsed for the first time and then repeatedly every interval. So you must start the timer somewhere else. In button button3_Click I assume
private void button3_Click(object sender, EventArgs e)
{
if (FullNameBOX.Text == "")
{
label5.Show();
timer1.Start();
}
else
{
... process the FullNameBOX.Text
}
}
In the Tick event handler stop the timer and hide the label
private void timer1_Tick(object sender, EventArgs e)
{
timer1.Stop();
label5.Hide();
}
Also, give better names to your controls. It's best to do so before creating the event handlers so that those get better names too. It is easier to understand messageLabel than label5 and SaveButton_Click than button3_Click.
I can't seem to get this loop to work.
Once the submit button is clicked ten times it should revert to the main form; instead it's reverting as soon as the submit is clicked once.
private void submit_Click(object sender, EventArgs e)
{
Form1 mainMenu = new Form1();
int repeat = 0;
do
{
num1.Text = A1.firstRandomNumber().ToString();
num2.Text = A1.secondRandomNumber().ToString();
repeat++;
} while (repeat <= 10);
if (repeat == 11)
{
mainMenu.Show();
this.Hide();
}
}
Everything inside of submit_Click occurs for each click. That includes defining repeat anew, setting it to 0, looping to increment it entirely to 11, and swapping which form is visible.
If you want to count the number of clicks, you'll have to establish your counter outside of the handler so it can be incremented:
private int repeatSubmit = 0;
private void submit_Click(object sender, EventArgs e)
{
if (repeatSubmit < 10)
{
num1.Text = A1.firstRandomNumber().ToString();
num2.Text = A1.secondRandomNumber().ToString();
repeatSubmit++;
}
else
{
mainMenu.Show();
this.Hide();
repeatSubmit = 0; // ready for the next time `this` form is shown
}
}
Just to clarify, you are waiting for the user to click the button 10 times? Or the loop is supposed to simulate 10 clicks?
This loop will enter (do) and set num1 and num2, add one to repeat, and then do that 10 times until repeat == 11, and then it will display the main menu.
I think the code you make be looking for is as follows:
private void submit_Click(object sender, EventArgs e)
{
...
repeat ++;
num1.Text = A1.firstRandomNumber().ToString();
num2.Text = A2.secondRandomNumer().ToString();
if(repeat >=10)
{
mainMenu.Show();
this.Hide();
}
}
As your code is, on 1 click you enter your loop where you proceed to increment the counter until it's equal to 11, then you exit your loop and show the main menu. Basically you're not counting clicks.
What you want to do is store the counter somewhere, probably as a class variable. Then every time you enter the click function you increment. When the click function has been entered 10 times then you would go into your if statement.
private int clickCount = 0;
private void submit_Click(object sender, EventArgs e){
clickCount++;
// Other code that happens on a click
if (clickCount == 10){ // 10th click show main menu
// Code to show main menu
}
}
It runs through the loop on the first click of submit, if I understand what you are trying to achieve, you don't need a loop at all, just a counter for each time the button is pressed.
I have an unusual thing happening with an RSS presenter I'm trying to make. It's meant to go to the next item after an 'Out' animation is played, then play the 'In' animation. http://oeis.org/A000217
void _timer_Tick(object sender, EventArgs e)
{
Storyboard sbOut = this.FindResource("sbAnimateOut") as Storyboard;
sbOut.Completed += new EventHandler(sbOut_Completed);
sbOut.Begin();
}
void sbOut_Completed(object sender, EventArgs e)
{
if (_selected < _total)
{
_selected++;
}
else
{
GetFeed(_feed);
_selected = 0;
}
lstbxItems.SelectedIndex = _selected;
counter.Text = _selected.ToString();
Storyboard sbIn = this.FindResource("sbAnimateIn") as Storyboard;
sbIn.Begin();
}
I noticed it seem to skip items though. When I step through it line by line, it seems to execute the void sbOut_Completed(object sender, EventArgs e) once the first time, three times the second time, six times the third time - and so on, sequentially.
Perhaps I'm going about this the wrong way and that's causing the issue? Any suggestions?
You are adding another event handler every timer tick!
Move this code:
sbOut.Completed += new EventHandler(sbOut_Completed);
into your initialization - only do it once.
I'm working on a windows App in C#, I have a for-loop which update something in a loop, and I have 3 buttons on the form named "Stop,Pause,Resume". So the purpose is as same as the buttons named. Does anyone know how to do this?
Here is the Loop
private void btnCompleteAuto_Click(object sender, EventArgs e)
{
setGeneralValue();
for (int i = 1; i <= autoGridView.Rows.Count - 1; i++)
{
if (SRP == "Pause") // this is what I was thinking but it won't work
{ // it will step into end-less loop
do // how to stop this loop on "Resume" button click
{
}while(SRP!="Resume")
}
car = false;
try
{
MemberID = Convert.ToInt64(autoGridView.Rows[0].Cells["Member_ID"].Value);
DispID = Convert.ToString(autoGridView.Rows[0].Cells["Disp_Id"].Value);
Mobile = Convert.ToString(autoGridView.Rows[0].Cells["Mobile"].Value);
DueDate = Convert.ToString(autoGridView.Rows[0].Cells["Due_Date"].Value);
}
catch (Exception)
{
MessageBox.Show("Row Not Found");
}
AutoRecharge(network_name, pack_name, Mobile, Mobile, Convert.ToString(autoGridView.Rows[0].Cells["Rck_Amt"].Value), vendor_id, vendor_pwd, pack_id, oxinetwork_id);
autoGridView.Rows.RemoveAt(0);
}
}
Here are the 3 button events in which I'm setting a variable
private void btnPause_Click(object sender, EventArgs e)
{
SRP = "Pause";
}
private void btnStop_Click(object sender, EventArgs e)
{
SRP = "Stop";
autoGridView.DataSource = "";
}
private void btnResume_Click(object sender, EventArgs e)
{
SRP = "Resume";
}
The reason this doesn't work as you expect is this:
A Windows Forms application uses a single UI thread, which continually processes incoming messages from a queue. Any event handlers you attach to the events of a Windows Forms control get sent to this queue and processed by the UI thread as quickly as possible.
Your btnCompleteAuto_Click is one such handler. Once it starts, nothing else will be processed by the UI thread until it exits. Thus any other handlers you attach to other events (btnPause_Click, btnStop_Click, etc.) must wait their turn, as they will run on the same (UI) thread.
If you want pause/resume functionality, this has to be achieved on a separate thread.
A possible way to implement it might be to use a BackgroundWorker, as suggested by saurabh.
Here is a rough sketch of what your updated code might look like (I have not even attempted to compile this, let alone debug it; it's intended only as a basic outline of how you might accomplish this functionality).
You need to be aware, however, that accessing UI controls directly from a non-UI thread is a no-no. Use a mechanism such as the BackgroundWorker.ProgressChanged event to handle any UI updates that you need to happen based on activity on a non-UI thread.
ManualResetEvent _busy = new ManualResetEvent(false);
private void btnCompleteAuto_Click(object sender, EventArgs e)
{
if (!backgroundWorker.IsBusy)
{
_busy.Set();
btnAutoCompleteAuto.Text = "Pause";
backgroundWorker.RunWorkerAsync();
}
else
{
_busy.Reset();
btnAutoCompleteAuto.Text = "Resume";
}
btnStop.Enabled = true;
}
private void btnStop_Click(object sender, EventArgs e)
{
_busy.Set();
backgroundWorker.CancelAsync();
}
private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
// for (something)
// {
_busy.WaitOne();
if (backgroundWorker.CancellationPending)
{
return;
}
// Do your work here.
// }
}
private void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
_busy.Reset();
btnAutoCompleteAuto.Text = "Start";
btnStop.Enabled = false;
}
After Reading your actual requirement in our comment , i would suggest that use Background worker class which supports cancellation of running process.
See here
I have a windows app which is just a form with a timer control on. I've managed to track this down to the following situation:
private void timer1_Tick(object sender, EventArgs e)
{
MessageBox.Show("Test");
timer1.Enabled = false;
}
Will print Test again and again until I stop the program. However:
private void timer1_Tick(object sender, EventArgs e)
{
//MessageBox.Show("Test");
textBox1.Text += "t";
timer1.Enabled = false;
}
Just adds a single "t" to the textbox.
Can anyone tell me why MessageBox.Show is causing the function to return before the timer is disabled?
The call to MessageBox.Show blocks execution of timer1_Tick until you close the messsagebox, so the call to set timer1.Enabled = false; doesn't occur until after that. Because of this, the timer is still running and thus timer_Tick` still keeps getting called, every time the timer fires, until you hit OK on one of the message boxes.
What you need, if you want displaying the messagebox to stop the timer from firing again, is:
private void timer1_Tick(object sender, EventArgs e)
{
timer1.Enabled = false;
MessageBox.Show("Test");
}
You disable the timer after the user clicked the messagebox away.
MessageBox.Show shows a modal dialog. It will return (to the caller method) after the user responded to the messagebox. If you disable the timer first, the event will not be triggered again, and the user will have enough time to react.
Try this:
timer1.Enabled = false;
MessageBox.Show("Test");
Are you clicking OK on test, each timer click? If the message boxes keep stacking up one on top of the other, it's because MessageBox.Show doesn't return until you close the messagebox. In the meantime a message pump will continue to run, and process your timer messages.