I am making a memory game. Whenever user clicks on a button, an image is revealed. Then user has to click on another button. If both images match, then buttons are replaced by a tick mark. If not, then there is a 1 sec gap for the user to memorize the image location..and then again, images are hidden and buttons are shown.
I do the 1 sec gap by
Thread.Sleep(1000)
I have embedded a countdown timer in the game whose duration is 30 sec. I have placed a label which shows the 30 second countdown on each clock tick.
Now the actual problem is, that whenever Thread.Sleep(1000) is invoked, the timer halts. And after 1 sec, it resumes. I want this timer to execute regardless of Thread. Please help.
It's a little hard to understand exactly what you are asking, so apologies if I've misunderstood you, but I think you are asking how you can update the UI using a timer on a new thread without blocking the UI thread? The answer is that you cannot update a UI control in a thread other than the one that it was created in. Instead you have to create a delegate to do it for you.
So, this gives you an exception because the callback UpdateText at the end of the timer executes on the timer thread, not the main UI thread:
private void button1_Click(object sender, EventArgs e)
{
System.Threading.Timer timer = new System.Threading.Timer(UpdateText, null, 1000, System.Threading.Timeout.Infinite);
}
public void UpdateText(object state)
{
this.textBox1.AppendText("Ouch!" + Environment.NewLine);
}
Whereas, this works as expected: When you click the button, one second later the word "Ouch!" appears in the text box. This is because the use of the BeginInvoke method on the textbox control with the MethodInvoker delegate causes the delegate to execute on the thread that owns the control (i.e. the main UI thread) rather than on the timer thread:
private void button1_Click(object sender, EventArgs e)
{
System.Threading.Timer timer = new System.Threading.Timer(UpdateText, null, 1000, System.Threading.Timeout.Infinite);
}
public void UpdateText(object state)
{
MethodInvoker action = delegate
{
this.textBox1.AppendText("Ouch!" + Environment.NewLine);
};
this.textBox1.BeginInvoke(action);
}
Related
Here's a C# code, What happens is when qsubmit button is clicked, program straight away displays "wait..!".
When I debug the program it is found that when I click and function executes textbox1.text = "Hello"; but doesn't updates textbox, it updates only when the control goes off the event function, when that happens value of textbox has already been changed to "wait..!". I want to know why it doesn't updates textbox instantly(If that would have done, I would have seen the text during Thread.Sleep())
private void Button_QSubmit_Click(object sender, EventArgs e)
{
textBox1.Text = "Hello";
Thread.Sleep(1000);
textBox1.Text = "Wait..!";
}
The UI thread is responsible to redraw the windows. So as long as you are doing this inside the UI Thread (e.g. a Button click event), the process is busy with your code and the window is not drawn.
A easy solution could be the use of an Timer. Just add an timer and in the button click you start it (e.g. you set itup to fire in 1 second).
The Timer Event then will simply set the Text.
https://msdn.microsoft.com/en-us/library/system.windows.forms.timer.aspx shows details about the Timer class.
You are hanging the UI Thread by calling Thread.Sleep from the Main Thread (UI), to update the text box you have to let the UI thread do its job outside your function to update the UI..anyway call Application.DoEvents() before the sleep. But calling Application.DoEvents() is a bad design
I want to make a button to perform some action and THEN let user know it was done. I tried making a label ander a button, then pause, then making it disappear.
private void button1_Click(object sender, EventArgs e)
{
// some action
label1.Text = "Done!";
System.Threading.Thread.Sleep(500);
label1.Text = "";
}
But it doesn't work. What is my mistake?
As Grant says in his answer, you're blocking the UI thread. The simplest solution is to spawn a new Task which will do the update for you, thus releasing the UI thread.
The Task can simply use Invoke to push the update back to the UI thread after a Sleep.
In your case, this translates to something like this:
private void button1_Click(object sender, EventArgs e)
{
// some action
label1.Text = "Done!";
new TaskFactory().StartNew(() =>
{
Thread.Sleep(5000);
Invoke((Action)(() => label1.Text = string.Empty));
});
}
The call to Thread.Sleep() freezes the UI thread for a half-second, so that no updates to the UI can happen (including your update to the Label's text).
Here's a couple options:
You could use a BackgroundWorker, which has built-in mechanisms for executing long-running code in a separate thread, and then updating the UI (such as your Label) when it's done.
You could add a Windows.Forms.Timer to your Form, to perform the action and update the Label. Give it an interval of 500 (ms), and it'll wait roughly a half-second before firing.
I have some simple C# code that is triggered on a Button Press. The button press first clears some ListBoxes, then changes the text of a label, and then calls a function.
private void button1_Click(object sender, EventArgs e)
{
listBox1.Items.Clear();
listBox2.Items.Clear();
listBox3.Items.Clear();
listBox4.Items.Clear();
label5.Text = "Getting links...";
process(url);
label5.Text = "Finished";
}
But the Lists are cleared and the label is changed after process() is finished executing. This ruins the purpose as I'm changing the label so that the user is aware that some action is taking place. How can I make the initial label change before the function process() finishes?
If your process method is long-running, it can cause UI freezing and prevent UI from redrawing - that's why you don't see your label text immediate update.
Simpliest way to achieve your goal - is call label5.Refresh() right after label5.Text = "Getting links...";, this will immediately cause invalidation and redrawing of label.
Or even you can call this.Refresh() if more than one control should be updated - this will update whole usercontrol or form owns your controls.
But note - if your process method runs a very long time (more than a 2-3 seconds for example) - you should consider doing it asyncroniously in thread separate from UI. It is considered as "good style" because it will not cause UI freezing.
You can use async keyword. Only when accessing the UI from different thread you have to use the Invoke
private async void button1_Click(object sender, EventArgs e)
{
await Task.Run(
() =>
{
this.Invoke((MethodInvoker)delegate
{
listBox1.Items.Clear();
listBox2.Items.Clear();
listBox3.Items.Clear();
listBox4.Items.Clear();
myLabel.Text = "Getting links...";
});
});
this.process(url);
await Task.Run(
() =>
{
this.Invoke((MethodInvoker)delegate { myLabel.Text = "Finished"; });
});
}
What about using a Task to run process(url) in a "thread" separated from GUI?
In this way GUI will stay responsive to the user ang got "refreshed", then, when your task ends, you just have to update GUI label.
When you have ops that must take a bit of time, you should always separate them from GUI. My two cents.
You have 2 options. either use a different thread to run process(url), or add before it Application.DoEvents().
I have a program that run in a loop. it's this
private void ReadCamAuto_Click(object sender, EventArgs e)
{
this.serialPort1.DataReceived -= new System.IO.Ports.SerialDataReceivedEventHandler(this.DataReceivedHandler);
RunReadCamAuto = true;
while (RunReadCamAuto)
{
serialPort1.WriteLine("2,2,2,2");
CreatePic(4, 4);
}
this.serialPort1.DataReceived += new System.IO.Ports.SerialDataReceivedEventHandler(this.DataReceivedHandler);
}
but the problem is then I'm in the While loop I cant press any other Button in my program so it is not possible to stop. I have no idea how to stop it ?
I tried to press a button who set the RunReadCamAuto to false and Console.ReadKey()
I'm Using:
c# Form App
MS VS 2010
You cannot expect user interface to work while the main thread is busy doing some work in a loop. Use BackgroundWorker object to fire desired loop in it - it's automatically invoked on other thread and from your main thread you can easily send the message to stop its work.
You need to assign your method to BackgroundWorker's DoWork event and then from your form just call myBackgroundWorker.RunWorkerAsync(). Then by calling myBackgroundWorker.CancelAsync() you will change its CancellationPending property to true, which you can be constantly checking in your loop to break execution.
Please see here.
I need to be able to disable a button for 1.5 seconds at a time for an application I'm writing. An image is displayed, a user clicks a button, and then another image is displayed. I need to make sure that the user doesn't click the button again too quickly.
So, when the image is displayed, I call this function:
//when a new image is displayed, start the timer and disable the 'done' button
//for 1.5 seconds, to force people to stop pressing next so quickly
System.Timers.Timer mTimer;
void TimerStart() {
Done.IsEnabled = false;
mTimer = new System.Timers.Timer();
mTimer.Interval = 1500;
mTimer.Start();
mTimer.Elapsed += new System.Timers.ElapsedEventHandler(TimerEnd);
}
The TimerEnd code looks like:
void TimerEnd(object sender, EventArgs eArgs) {
if (sender == mTimer){
Done.IsEnabled = true;
mTimer.Stop();
}
}
The 'Done.IsEnabled' line gets hit, but the button is not reenabled and the timer doesn't stop firing. What am I doing wrong here? If it matters, this is a WPF app.
Use DispatcherTimer instead
DispatcherTimer timer = new DispatcherTimer();
timer.Interval = TimeSpan.FromMilliseconds(someInterval);
timer.Tick += new EventHandler(someEventHandler);
timer.Start();
private void someEventHandler(Object sender, EventArgs args)
{
//some operations
//if you want this event handler executed for just once
// DispatcherTimer thisTimer = (DispatcherTimer)sender;
// thisTimer.Stop();
}
Basically you are trying to debounce the button, to prevent too quick clicks. Rather than use a timer save the previous click time in millis, if the button is clicked again within a short time ignore the next event.
The timer event is raised on a different thread. When working with the winforms controls, you need to make sure you Invoke them from the same thread where they were called.
When working with WPF there is no guarantee that updates made to UI controls on non-UI threads will work as expected. In many cases you will get an exception when you do this.
In your Timer elapsed handler you need to use the BeginInvoke/EndInvoke paradigm and put your button enabling logic in there to ensure that this code runs on the UI thread instead of Begin/End Invoke
There is a SynchnornizationContext available as well which can be accessed by calling SynchronizationContext.Current . You'll need to cache this before you make the timer call since SynchronizationContext.Current will be null in non-UI threads.
This link talks about this as well.