I have a button on which a click and it takes a screenshot which i display in my Picture Box. I dont face issue with this code:
private void btnScreenShot_Click(object sender, EventArgs e)
{
btnSave.Visible = true;
sendto_bmpbox.Image = CaptureScreen();
}
However when i loop the entire Form freezes and i cannot click on anything:
private void btnScreenShot_Click(object sender, EventArgs e)
{
// Freezes here
btnSave.Visible = true;
while(flag == 0)
{
sendto_bmpbox.Image = CaptureScreen();
}
}
How do i fix this problem?
That's because your while() is infinite. What makes flag change from capture to capture?
In case you want to infinitely capture the screen - never use the main thread for such things, as it will cause it to hang and prevent your application from updating the UI.
Use the BackgroundWorker class for things like that, you can use this example.
private void button1_Click(object sender, EventArgs e)
{
btnSave.Visible = true;
Thread thread = new Thread(new ThreadStart(threadWork));
thread.Start();
}
int flag = 0;
private void threadWork()
{
while (flag == 0)
{
UpdateImage();
}
}
private void UpdateImage()
{
if (this.InvokeRequired)
{
this.Invoke(UpdateImage);
}
else
{
sendto_bmpbox.Image = CaptureScreen();
}
}
Try Application.DoEvents in loop. I think this can help you...
private void btnScreenShot_Click(object sender, EventArgs e)
{
// Freezes here
btnSave.Visible = true;
while(flag == 0)
{
Application.DoEvents();
sendto_bmpbox.Image = CaptureScreen();
}
}
Related
i have a simple question and answer type program, with a bit of code like this:
private void AskQuestion(Question q)
{
questionbox.Text = q.GetQuestion();
answering = true;
while (answering == true)
{
}
if (q.GetQuestion() == answerbox.Text)
{
MessageBox.Show("well done");
}
else
{
MessageBox.Show("nope");
}
}
answering is just a toggle that i have so the program doesn't test for the answer until the user has put the answer in and clicked a button.
i have a button for user to click, which switches it over to false:
private void Answer_Click(object sender, EventArgs e)
{
answering = false;
}
The idea is that the while loop pauses the program and exits when the user has answered the question, but it just freezes the whole thing.
I tried slowing it down with thread sleeping, then I went for a timer watching the variable, tried it on a new thread, but the threads wouldn't talk to each other, so I'm in this silly situation where I'm stuck.
Please help programmers, and suggest a strategy for me here?
You could just store the Question in a field and put the Answer logic in the Answer_Click
private Question _currentQuestion;
private void AskQuestion(Question q)
{
_currentQuestion = q.GetQuestion();
questionbox.Text =_currentQuestion;
}
private void Answer_Click(object sender, EventArgs e)
{
if (_currentQuestion != null)
{
if (_currentQuestion == answerbox.Text)
{
MessageBox.Show("well done");
}
else
{
MessageBox.Show("nope");
}
}
}
Here is example:
private void button2_Click(object sender, EventArgs e)
{
hey = true;
Thread thread = new Thread(new ThreadStart(AskQuestion));
thread.Start();
}
bool hey;
void AskQuestion()
{
while (hey)
{
}
MessageBox.Show("Done");
}
private void answer_Click(object sender, EventArgs e)
{
hey = false;
}
This shows MessageBox when answer_Click() pressed. It doesn't freeze.
I am new in C#. I found some code which work on progressbar. What is does, when someone click on button start btnStartAsyncOperation_Click the progress bar starts increasing and when btnCancel_Click is pressed it cancel the operation. Here is the code
namespace BackgroundWorkerSample
{
public partial class Form1 : Form
{
BackgroundWorker m_oWorker;
public Form1()
{
InitializeComponent();
m_oWorker = new BackgroundWorker();
m_oWorker.DoWork += new DoWorkEventHandler(m_oWorker_DoWork);
m_oWorker.ProgressChanged += new ProgressChangedEventHandler(m_oWorker_ProgressChanged);
m_oWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(abcd);
m_oWorker.WorkerReportsProgress = true;
m_oWorker.WorkerSupportsCancellation = true;
}
void abcd(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Cancelled)
{
lblStatus.Text = "Task Cancelled.";
}
else if (e.Error != null)
{
lblStatus.Text = "Error while performing background operation.";
}
else
{
lblStatus.Text = "Task Completed...";
}
btnStartAsyncOperation.Enabled = true;
btnCancel.Enabled = false;
}
void m_oWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
progressBar1.Value = e.ProgressPercentage;
lblStatus.Text = "Processing......" + progressBar1.Value.ToString() + "%";
}
void m_oWorker_DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 0; i < 100; i++)
{
Thread.Sleep(100);
m_oWorker.ReportProgress(i);
if (m_oWorker.CancellationPending)
{
e.Cancel = true;
m_oWorker.ReportProgress(0);
return;
}
}
//Report 100% completion on operation completed
m_oWorker.ReportProgress(100);
}
private void btnStartAsyncOperation_Click(object sender, EventArgs e)
{
btnStartAsyncOperation.Enabled = false;
btnCancel.Enabled = true;
//Start the async operation here
m_oWorker.RunWorkerAsync();
}
private void btnCancel_Click(object sender, EventArgs e)
{
if (m_oWorker.IsBusy)
{
//Stop/Cancel the async operation here
m_oWorker.CancelAsync();
}
}
private void progressBar1_Click(object sender, EventArgs e)
{
}
private void lblStatus_Click(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
}
private void button2_Click(object sender, EventArgs e)
{
}
}
}
Now I added 2 more button, button1 to pause and button2 to resume. Since I could not find any method to resume, I had to use CancelAsync() function when I press pause and I keep the value of progress bar in a global variable. Then when I press resume I start the progress bar again using RunWorkerAsync. But the problem is, I can not send the value of global variable in this function so it start from 0 progress.
I tried to use thread.sleep(infinite time here) when someone press pause and then stop the thread when someone press resume. Still the problem is, I can not press any button in this situation. Still if I enable button they don't work.
Please give me some solution.
You could try having your own variable, i.e
bool isPaused = false;
When someone clicks your pause button...
isPaused = true;
And set it to false when someone clicks resume. Finally, in your for loop in your doWork method, make it wait until that variable is false.
while (isPaused)
{
Thread.Sleep(100);
}
Let me know how this works out for you.
This is how I did it in my code:
In the backgroundWorker DoWork event I did:
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
_busy.WaitOne();
this.Invoke(new MethodInvoker(delegate { label2.Text = "Website To Crawl: "; }));
this.Invoke(new MethodInvoker(delegate { label4.Text = mainUrl; }));
webCrawler(mainUrl, levelsToCrawl, e);
}
Then in the pause button click event I did:
private void button4_Click(object sender, EventArgs e)
{
_busy.Reset();
}
In the resume button click event I did:
private void button5_Click(object sender, EventArgs e)
{
_busy.Set();
}
But it's not working when I click to start the process:
private void button1_Click(object sender, EventArgs e)
{
backgroundWorker1.RunWorkerAsync();
button1.Enabled = false;
this.Text = "Processing...";
label6.Text = "Processing...";
label6.Visible = true;
button2.Enabled = false;
checkBox1.Enabled = false;
checkBox2.Enabled = false;
numericUpDown1.Enabled = false;
button3.Enabled = true;
}
Nothing happen only when I click the resume button the process start then when I click the pause button nothing happen.
I want that when I click the start process button it will start the backgroundWorker regular then when clicking the pause button it will pause and the resume button it will resume.
What did I do wrong ? Can someone fix my code ?
In your BackgroundWorker thread code, you need to find places that are safe to "pause" execution. The ManualResetEvent is the right way to code. This other post might help:
Is there a way to indefinitely pause a thread?
Basically, in a few choice points in your worker thread code where you want to allow it to pause, try inserting:
_busy.WaitOne(Timeout.Infinite);
And when you want to pause (from your main thread) you use:
_busy.Reset();
And to resume:
_busy.Set();
You should be able to do this using the ManualResetEvent like this ...
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
_busy.WaitOne();
test(mainUrl, levelsToCrawl, e);
}
... and then when you want to pause the thread call _busy.Reset() ... and when you want to restart it call _busy.Set().
Additionally, you can place _busy.WaitOne(); anywhere you want to pause.
I've been looking for the answer of this thread but I come up with my own solution i made and i just wanna share it with you. hope this works.
I have a background worker and i want to pause it when i hit close button of my form. asking "You are about to cancel the process" so it should pause the process.
declare bool pauseWorker = false; on your class.
private void bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
while (condition)
{
if (pauseWorker == true)
{
while (pauseWorker == true)
{
if (pauseWorker == false) break;
}
}
else
{
//continue process... your code here
}
}
}
private void frmCmsnDownload_FormClosing(object sender, FormClosingEventArgs e)
{
if (bgWorker.IsBusy)
{
pauseWorker = true; //this will trigger the dowork event to loop that
//checks if pauseWorker is set to false
DiaglogResult x = MessageBox.Show("You are about cancel the process", "Close", MessageBoxButtons.YesNo);
if (x == DialogResult.Yes) bgWorker.CancelAsync();
else
{
e.Cancel = true;
pauseWorker = false; //if the user click no
//the do work will continue the process
return;
}
}
}
Therefore the main solution here is the boolean declaration that controls the DoWork event of BGWorker.
Hope this solution helps your problem. Thank you.
I use a simple class that utilizes System.Thread.Monitor and lock()...
public class ThreadPauseState {
private object _lock = new object();
private bool _paused = false;
public bool Paused {
get { return _paused; }
set {
if(_paused != value) {
if(value) {
Monitor.Enter(_lock);
_paused = true;
} else {
_paused = false;
Monitor.Exit(_lock);
}
}
}
}
public void Wait() {
lock(_lock) { }
}
}
Using it is very simple...
private ThreadPauseState _state = new ThreadPauseState();
private void btnPause_Click(object sender, EventArgs e) {
_state.Paused = true;
}
private void btnResume_Click(object sender, EventArgs e) {
_state.Paused = false;
}
private void btnCancel_Click(object sender, EventArgs e) {
backgroundWorker1.CancelAsync();
_state.Paused = false; // needed if you cancel while paused
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e) {
var worker = (BackgroundWorker)sender;
for(var _ = 0; _ < 100; _++) {
_state.Wait();
if(worker.CancellationPending) return;
Thread.Sleep(100); // or whatever your work is
}
}
This works for me:
bool work = true;
backgroundWorker1.WorkerReportsProgress = true;
backgroundWorker1.DoWork += backgroundWorker1_DoWork;
backgroundWorker1.ProgressChanged += myChangeFunction;
backgroundWorker1.RunWorkerAsync();
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
while (true && work)
{
// Your code here
backgroundWorker1.ReportProgress(0);
Thread.Sleep(1000);
}
e.Cancel = true;
}
private void myChangeFunction(object sender, ProgressChangedEventArgs e)
{
// Here you can change label.text or whatever thing the interface needs to change.
}
private void Stop()
{
work = false;
}
private void Start()
{
work = true;
backgroundWorker1.RunWorkerAsync();
}
NOTE: If you want to change something of the interface, you have to put it in the myChangeFunction(), because in the DoWork() function will not work. Hope this helps.
Looking for some help on a problem Im having
sorry if this question has already been asked, I can not find anything similar.
The idea is when a picturebox is clicked changed the image to ON.
If the picture box is held for more than 2 seconds to open a new form and leave the picturebox as OFF.
However if the picturebox is clicked ON and then held for 2 seconds and then returns i need the picturebox state to remain ON.
Here is what I have tried so far.
I believe for this to work correctly I need to stop MouseUp event from occuring.
Is there a way I can stop MouseUp when Tick occurs?
Is there a easier / better way to do this?
Any help would be appreciated.
private void time_HoldDownInternal_Tick(object sender, EventArgs e)
{
time_HoldDownInternal.Enabled = false;
time_HoldDownInternal.Interval = 1000;
form1show.Visible = true;
}
private void pb_pictureBoxTest_MouseDown(object sender, MouseEventArgs e)
{
mainMenuVariables.mousedown = true;
time_HoldDownInternal.Enabled = true;
}
private void pb_pictureBoxTest_MouseUp(object sender, MouseEventArgs e)
{
mainMenuVariables.mousedown = false;
//MessageBox.Show("mouse up");
time_HoldDownInternal.Enabled = false;
time_HoldDownInternal.Interval = 1000;
}
private void pb_pictureBoxTest_Click(object sender, EventArgs e)
{
if (mainMenuVariables.mousedown == true)
{
if (mainMenuVariables.pictureBox == false)
{
mainMenuVariables.pictureBox = true;
pb_pictureBoxTest.Image = new Bitmap(mainMenuVariables.pictureBoxOn);
return;
}
if (mainMenuVariables.pictureBox == true)
{
mainMenuVariables.pictureBox = false;
pb_pictureBoxTest.Image = new Bitmap(mainMenuVariables.pictureBoxOff);
return;
}
}
if (mainMenuVariables.mousedown == false)
{
//nothing
}
}
Rather than starting a timer, just record the current time on mouse down. Then in mouse up, check if it has been 2 seconds. e.g:
private void pb_pictureBoxTest_MouseDown(object sender, MouseEventArgs e)
{
mainMenuVariables.mousedown = true;
mainMenuVariables.mousedowntime = DateTime.Now;
}
private void pb_pictureBoxTest_MouseUp(object sender, MouseEventArgs e)
{
mainMenuVariables.mousedown = false;
var clickDuration = DateTime.Now - mainMenuVariables.mousedowntime;
if ( clickDuration > TimeSpan.FromSeconds(2))
{
// Do 'hold' logic (e.g. open dialog, etc)
}
else
{
// Do normal click logic (e.g. toggle 'On'/'Off' image)
}
}
I have a WPF form which runs a background operation with progress bar. but the problem is that;
when the operation is completed, the progress bar is still running. I mean it shows like the operation is in progress.
how can I stop that? here is my whole code;
System.ComponentModel.BackgroundWorker mWorker;
private void button1_Click(object sender, RoutedEventArgs e) {
mWorker = new System.ComponentModel.BackgroundWorker();
mWorker.DoWork +=new System.ComponentModel.DoWorkEventHandler(worker_DoWork);
mWorker.ProgressChanged +=new System.ComponentModel.ProgressChangedEventHandler(worker_ProgressChanged);
mWorker.WorkerReportsProgress = true;
mWorker.WorkerSupportsCancellation = true;
mWorker.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
mWorker.RunWorkerAsync();
while (pbProcessing.Value != 100) {
if (!mWorker.CancellationPending) {
try {
pbProcessing.Value = (pbProcessing.Value + 0.01) % 100;
} catch (System.Exception ex) {
// No action required
}
} else {
MessageBox.Show(this, "Process cancelled", "Cancel Process", MessageBoxButton.OK);
break;
}
System.Windows.Threading.Dispatcher.CurrentDispatcher.Invoke(System.Windows.Threading.DispatcherPriority.Background,
new System.Threading.ThreadStart(delegate { }));
}
}
private void worker_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e) {
// Do your work here, its on seperate thread
System.Threading.Thread.Sleep(10000);
}
private void worker_ProgressChanged(object sender, System.ComponentModel.ProgressChangedEventArgs e) {
pbProcessing.Value = e.ProgressPercentage;
}
private void worker_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e) {
// Stop Progressbar updatation
Window1 w = new Window1();
w.Browser.Navigate(new Uri("http://stackoverflow.com"));
w.Show();
}
private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e) {
if (mWorker != null) {
if (mWorker.IsBusy) {
mWorker.CancelAsync();
}
}
}
If you want to hide the progressbar after the work is done, set its Visibility property to Visibility.Hidden. If you just want to reset it to its initial state, set it's Value to 0 (or to pbProgressing.Minimum, if you changed that from its default value).
As a side note, your code doesn't really make sense: Instead of continuously changing pbProcessing.Value in the button event handler (which is completely useless, since no UI updates are performed until the button event handler has completed), you should only change the value in ProgressChanged. I.e., your code should look something like this:
System.ComponentModel.BackgroundWorker mWorker;
private void button1_Click(object sender, RoutedEventArgs e) {
mWorker = new System.ComponentModel.BackgroundWorker();
mWorker.DoWork +=new System.ComponentModel.DoWorkEventHandler(worker_DoWork);
mWorker.ProgressChanged +=new System.ComponentModel.ProgressChangedEventHandler(worker_ProgressChanged);
mWorker.WorkerReportsProgress = true;
mWorker.WorkerSupportsCancellation = true;
mWorker.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
mWorker.RunWorkerAsync();
// Don't do anything else here
}
private void worker_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e) {
for (int i = 1; i < 100; i++) {
mWorker.ReportProgress(i);
// Do some part of the work
System.Threading.Thread.Sleep(100);
// Check if the user wants to abort
if (mWorker.CancellationPending) {
e.Cancel = true;
return;
}
}
mWorker.ReportProgress(100); // Done
}
private void worker_ProgressChanged(object sender, System.ComponentModel.ProgressChangedEventArgs e) {
pbProcessing.Value = e.ProgressPercentage;
}
private void worker_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e) {
// Stop Progressbar updatation
Window1 w = new Window1();
w.Browser.Navigate(new Uri("http://stackoverflow.com"));
w.Show();
// Check the result
if (e.Cancelled) {
// show the message box that the task has been canceled
}
// Reset Progress bar
pbProcessing.Value = 0;
}
private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e) {
if (mWorker != null) {
if (mWorker.IsBusy) {
mWorker.CancelAsync();
}
}
}