I would like to kill the first thread upon the second click, then re-create it. My goal is to only ever have one tick thread in existence.
I believe I can do this with supplying a delegate to the thread instance? but I have googled and fiddled with it for hours upon hours with no luck. Can anyone translate my anonymous lambda expression into something with a delegate so I can identify and kill my thread after I've started it?
I hope my question makes sense, I am still learning... thanks
Timer timer1 = new Timer();
timer1.Interval = 1000;
timer1.Start();
private void button1_Click(object sender, EventArgs e)
{
//If I click button twice, how do I kill the first tick thread,
//before creating another?
timer1.Tick += (sender2, e2) => timer1_Tick(sender2, e2, 1, "text");
}
private void timer1_Tick(object sender, EventArgs e, int num, string text)
{
//do stuff with num and text
}
All you have to do is create a variable to store the delegate -- that should be of type Action<object, EventArgs>. So something like this:
private Action<object, EventArgs> _handler;
private void button1_Click(object sender, EventArgs e)
{
if (_handler != null)
timer1.Tick -= _handler;
_handler = (sender2, e2) => timer1_Tick(sender2, e2, 1, "text");
timer1.Tick += _handler;
}
private void timer1_Tick(object sender, EventArgs e, int num, string text)
{
timer1.Tick -= _handler;
_handler = null;
//do stuff with num and text
}
Note that this creates a race condition -- the "_handler" reference could be set to null by a "timer1_Tick" thread after the other thread sets the reference, but before it adds it to the "Tick" event. (To avoid the race condition, you would want to create a local copy of "_handler".) Hopefully that gives you the idea though ...
Related
I have a desktop WPF application that at some point needs to do something on a timely basis. Suppose I use DispatcherTimer class. There's a "long" way:
public MainWindow()
{
// dozens lines of code
timer1.Interval = new TimeSpan(0, 0, 1);
timer1.Tick += timer1_Tick;
}
// hundreds lines of code later
DispatcherTimer timer1 = new DispatcherTimer();
void timer1_Tick(object sender, EventArgs e)
{
// do stuff
}
void checkBox1_CheckedChanged(object sender, EventArgs e)
{
timer1.IsEnabled = checkBox1.IsChecked.Value;
}
It works ok, but I don't like that timer-related code is separated in two parts. I could re-create timer each time I start it:
DispatcherTimer timer1;
void timer1_Tick(object sender, EventArgs e)
{
// do stuff
}
void checkBox1_CheckedChanged(object sender, EventArgs e)
{
timer1 = new DispatcherTimer();
timer1.Interval = new TimeSpan(0, 0, 1);
timer1.Tick += timer1_Tick;
timer1.IsEnabled = checkBox1.IsChecked.Value;
}
but that feels wrong.
Also DispatcherTimer have constructor that take EventHandler as an argument that I may use kinda like that:
DispatcherTimer timer1 = new DispatcherTimer(
new TimeSpan(0,0,1),
DispatcherPriority.SystemIdle,
new EventHandler(timer1_Tick),
Dispatcher.CurrentDispatcher);
void timer1_Tick(object sender, EventArgs e)
{
// do stuff
}
void checkBox1_CheckedChanged(object sender, EventArgs e)
{
timer1.IsEnabled = checkBox1.IsChecked.Value;
}
I like it, it's simple and compact, but you can't create EventHandler this way, the compiler says "A field initializer cannot reference the non-static field, method or blah-blah-blah".
Is there a way to make this nice code actually work?
What's wrong with just doing it all in the constructor? That's how I normally do it:
private DispatcherTimer _timer1;
public MainWindow()
{
// dozens lines of code
_timer1 = new DispatcherTimer(TimeSpan.FromSeconds(1),
DispatcherPriority.SystemIdle,
timer1_Tick,
Dispatcher);
}
if you don't mind changing field to property (with backing field), you can do initialization in getter (only on first read):
DispatcherTimer _timer1;
DispatcherTimer timer1
{
get
{
return _timer1 ??= new DispatcherTimer
(
new TimeSpan(0, 0, 1),
DispatcherPriority.SystemIdle,
new EventHandler(timer1_Tick),
Dispatcher.CurrentDispatcher
);
}
}
void timer1_Tick(object sender, EventArgs e)
{
// do stuff
}
you could just create the timer in the constructor instead. Optionally with a local function or lambda for the handler to keep it close to the initialization.
If you follow the stylecop code style rules the code should be ordered as
Fields
Constructors
...
methods
So if there are hundreds of lines of code between the declaration and initialization of your timer there might be other design issues you need to address first.
If you have multiple constructors you should have one constructor that is guaranteed to run, and that all the other delegates some of the construction to.
Here's my code
private void checkBox1_CheckedChanged(object sender, EventArgs e)
{
System.Timers.Timer myTimer = new System.Timers.Timer();
myTimer.Elapsed += new ElapsedEventHandler(DisplayTimeEvent);
myTimer.Interval = Convert.ToInt32(textBox5.Text);
if (checkBox1.Checked)
{
myTimer.Start();
}
else
{
myTimer.Stop();
}
}
It should stop repeating the function when unchecked, but it doesn't. What's wrong with it?
I recommend that you stop using System.Timers.Timer and start using a System.Windows.Forms.Timer component.
Begin by removing your myTimer-related code (the entire body of checkBox1_CheckedChanged will need to be replaced with code from below.)
Add a Timer component to your form using the designer and name it myTimer. This will add a System.Windows.Forms.Timer field to your form called myTimer.
Using the designer, set the Tick event handler of myTimer to DisplayTimeEvent. (Or add a new handler and replace its code with the code of your DisplayTimeEvent function.)
Then change your checkBox1_CheckedChange function to look like this:
private void checkBox1_CheckedChanged(object sender, EventArgs e)
{
if (int.TryParse(textBox5.Text, out int interval)) {
this.myTimer.Interval = interval;
}
this.myTimer.Enabled = checkBox1.Checked;
this.textBox5.Enabled = !checkBox1.Checked;
}
I also recommend adding the following handler to textBox5 to perform the bare minimum validation so you can't crash your app by entering an interval of 0 or the empty string, or some text that is not an integer.
private void textBox5_TextChanged(object sender, EventArgs e)
{
this.checkBox1.Enabled = (int.TryParse(textBox5.Text, out int interval) && interval > 0);
}
The System.Windows.Forms.Timer's Tick handler will be called in the UI thread, meaning it will be safe to do things like update labels of your form in that handler. In contrast to that, the System.Timers.Timer will be called on a worker thread and will require that you take on some some thread-management responsibilities you likely don't want to incur, such as invoking your UI updates back to the main UI thread. See Why there are 5 Versions of Timer Classes in .NET? for more info.
Everytime checkbox1 is changed, new Timer is created. When checkbox is ticked, created timer is active and will invoke DisplayTimeEvent forever. When checkbox is unticked, you stop another Timer, which was just created.
You need to create Timer only once (probably when form is created), or when checkbox1 is changed first time:
private System.Timers.Timer myTimer;
private void checkBox1_CheckedChanged(object sender, EventArgs e)
{
if (myTimer == null) {
myTimer = new System.Timers.Timer();
myTimer.Elapsed += new ElapsedEventHandler(DisplayTimeEvent);
myTimer.Interval = Convert.ToInt32(textBox5.Text);
}
if (checkBox1.Checked)
{
myTimer.Start();
}
else
{
myTimer.Stop();
}
}
I have event
button.Click += ProcessClick;
and my event handler ProcessClick is:
private void async ProcessClick(object o, EventArgs e){
await LongOperation()
}
When I will click button quickly many times,
How to process only the first thread and skip other threads, until the first is done?
Disabling button after first click is not a solution...
EDIT: utilizing any type of thread constructions is acceptable: Tasks, Semaphores, locks and so on.
You can remove the event after the first click and add it again at the end of processing the first click.
private async void button1_Click(object sender, EventArgs e)
{
Debug.Write("Running click event");
this.button1.Click -= button1_Click;
await Task.Run(() => Task.Delay(5000));
this.button1.Click += button1_Click;
}
private bool longOperationRunning;
private void async ProcessClick(object o, EventArgs e){
if (longOperationRunning)
return;
longOperationRunning = true;
await LongOperation()
longOperationRunning = false;
}
This question is a bit obscure, however I cannot find an answer for it anywhere. I am writing a program in C# (Visual Studio Pro 2013) and I need to perform an action after the user has stopped typing for 2 seconds (setting the interval at 2000). I would need a standard timer for this however I need to detect when the user has stopped typing for 2 seconds. How would I go about doing this?
Here's the complete code:
public partial class Form1 : Form
{
System.Timers.Timer timer;
public Form1()
{
InitializeComponent();
// Initialize the timer.
timer = new System.Timers.Timer();
timer.Interval = 2000; // = 2 seconds; 1 second = 1000 miliseconds
timer.Elapsed += OnElapsed;
}
// Handles the TextBox.KeyUp event.
// The event handler was added in the designer via the Properties > Events > KeyUp
private void textBox1_KeyUp(object sender, System.Windows.Forms.KeyEventArgs e)
{
// Reset the timer on each KeyUp.
timer.Stop();
timer.Start();
}
private void OnElapsed(object source, ElapsedEventArgs e)
{
// When time's up...
// - stop the timer first...
timer.Stop();
// - do something more...
MessageBox.Show("Time out!");
}
}
king.code's answer would be correct if you just reset the timer in the first line of textBox1_KeyUp event and initialize the timer in constructor or main method depending on usage.
System.Timers.Timer timer;
private void textBox1_KeyUp(object sender, System.Windows.Forms.KeyEventArgs e)
{
timer.Stop();
timer.Start();
timer.Elapsed += new ElapsedEventHandler(OnTimedEvent);
}
private static void OnTimedEvent(object source, ElapsedEventArgs e)
{
// Do something
}
I would recommend you go for class that inherits text box and pass timer into it if you are going to use it at multiple places
Try this:
System.Timers.Timer timer = new System.Timers.Timer(2000);;
timer.Elapsed += new ElapsedEventHandler(OnTimedEvent);
timer.Enabled = false;
private void textBox1_KeyUp(object sender, System.Windows.Forms.KeyEventArgs e)
{
timer.Enabled = false;
timer.Enabled = true;
}
private static void OnTimedEvent(object source, ElapsedEventArgs e)
{
// Do something
timer.Enabled = false;
}
That is easy just create a timer that sets to 2000 Ms and handle
It by the text change interveral .
Ex:
Set an integer that count from 0 to 2000 then increase it by the
Timer if user starts typing then reset the number else keep
Counting till reach 2000 an ping do the rusty homeboy helped;)
I have just found a valid answer that is simple and compact. I will explain it first and then show a code example. You need to start the timer disabled, and then you need to enable it as soon as the the user presses a key. Then, while still in the method for the user pressing the button you would need to reset the timer interval back to 2000. Whenever the timer expires, you do the action that needs to happen when the keyboard has been inactive for 2 seconds. Code example:
private void textBox_KeyPress(object sender, KeyPressEventArgs e)
{
this.timer.Enabled = true;
this.timer.Interval = 2000;
}
Now the method for the timer_Tick:
private void timer_Tick(object sender, EventArgs e)
{
//Do something when the keyboard has been inactive in 2 seconds
}
Currently I'm moving from java to c# and I'm full of crazy questions.
I'm trying new things on a windows form application and now,I would like to create a loop wich is executing a code every 1 minute,the problem is that I have no idea where to put this code.
For example,the form structure is like:
using System;
namespace Tray_Icon
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
notifyIcon1.ShowBalloonTip(5000);
}
private void notifyIcon1_BalloonTipClicked(object sender, EventArgs e)
{
label1.Text = "Baloon clicked!";
}
private void notifyIcon1_BalloonTipClosed(object sender, EventArgs e)
{
label1.Text = "baloon closed!";
}
private void contextMenuStrip1_Opening(object sender, CancelEventArgs e)
{
}
private void option1ToolStripMenuItem_Click(object sender, EventArgs e)
{
//some code here
}
private void option2ToolStripMenuItem_Click(object sender, EventArgs e)
{
//some code here
}
private void option3ToolStripMenuItem_Click(object sender, EventArgs e)
{
label1.Text = "Option 3 clicked!";
}
private void notifyIcon1_MouseDoubleClick(object sender, MouseEventArgs e)
{
option1ToolStripMenuItem_Click(this, null);
}
private void closeToolStripMenuItem_Click(object sender, EventArgs e)
{
this.Close();
}
private void btnWrite_Click(object sender, EventArgs e)
{
//code here
}
}
}
Where should I put the loop code? :(
Thanks in advance for ANY replay!!!
Add a Timer to your form:
set its Interval property to 60000 (one minute in milliseconds) and Enabled to True:
and attach an event handler to the Timer.Tick event, e.g. by double-clicking the timer in the Forms designer:
private void timer1_Tick(object sender, EventArgs e)
{
// do something here. It will be executed every 60 seconds
}
You would have to add a timer, and set the interval to 1000 miliseconds, and in the OnTick event you add the code with your loop
Timer tmr = null;
private void StartTimer()
{
tmr = new Timer();
tmr.Interval = 1000;
tmr.Tick += new EventHandler<EventArgs>(tmr_Tick);
tmr.Enabled = true;
}
void tmr_Tick(object sender, EventArgs e)
{
// Code with your loop here
}
You can't put any loop code in here.
In your designer look for the Timer control. When you have that, configure it to run every minute and place your code in the Timer_Tick event.
Or create a timer manually in code and respond to the event :) But for starters, doing it by the designer is easier!
Drag a Timer component on the Form and doubleclick it. There you go with the code.
The Timer component runs in the main thread so you can modify UI components without worrying.
Alternatively You could create a System.Timers.Timer, which has it's own thread and has some advantages, but possible caveats when modifying UI components. See http://msdn.microsoft.com/en-us/library/system.timers.timer.aspx
Try to use Background Worker and put the code in the backgroundWorker.DoWork or use a Timer
Use System.Timers.Timer:
System.Timers.Timer aTimer;
{
aTimer = new System.Timers.Timer();
aTimer.Elapsed += new ElapsedEventHandler(OnTimedEvent);
aTimer.Interval = 60000;
aTimer.Enabled = true;
}
private static void OnTimedEvent(object source, ElapsedEventArgs e)
{
Console.WriteLine("The Elapsed event was raised at {0}", e.SignalTime);
}
for using Timer see this tutorial: C# Timer
How you do it in Java platform?
I think Java should be the same with .net.
In fact, a form program is just normal program which contains a event dispatcher. The event dispatcher listen to the UI events and dispatch them to the event handlers. I think all the UI mode should like this, no matter Java or .net platform.
So generally speaking, you have 2 options:
Start the loop at beginning. In this case, you should insert your
code in the constructor of the Form.
Start the loop when user
click the button. In this case, you should insert your code in the
event handler function.
Yes, as others mentioned, you should use the timer. But this should after you know where your code should locate. You also can use a endless loop with a sleep call. But timer is a better solution.
Idea of timer is more better. But If you want to use threads. Then Follow this
Let me assume that You want to do it right from the start of program
You can write in body of function (event in fact) named Form1_Load as
Your actual code is just within while loop other code only to guide
I can guide if you don't know the use of threads in C#
bool button2Clicked = false;
private void Form1_Load(object sender, EventArgs e)
{
// A good Way to call Thread
System.Threading.Thread t1 = new System.Threading.Thread(delegate()
{
while (!button2Clicked)
{
// Do Any Stuff;
System.Threading.Thread.Sleep(60000); //60000 Millieconds=1M
}
});
t1.IsBackground = true; // With above statement Thread Will automatically
// be Aborted on Application Exit
t1.Start();
}