On the face of it it seems quite simple.
I have a switch case and if the condition is met I would like to print text to a label with a animation.
in this case a type writer animation.
I have already made the animation however I cant seem to integrate a similar version it into the switch case itself.
Any help?
Type Writer Animation code c#:
public partial class Form1 : Form
{
int _charIndex = 0;
string _text = "This is a test.";
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
_charIndex = 0;
label1.Text = string.Empty;
Thread t = new Thread(new ThreadStart(this.TypewriteText));
t.Start();
}
private void TypewriteText()
{
while (_charIndex < _text.Length)
{
Thread.Sleep(50);
label1.Invoke(new Action(() =>
{
label1.Text += _text[_charIndex];
}));
_charIndex++;
}
}
}
}
And the animation code needs to be placed into this:
Switch case code:
void TestEngine(object sender, SpeechRecognizedEventArgs e)
{
switch (e.Result.Text)
{
case "Test":
//Label animation code goes here
break;
Thanks in advance!
Short answer - move the code in a method and call it from anywhere you want.
Long answer
While it works, it doesn't make sense because all the worker thread does is sleeping and then calling the UI thread. System.Windows.Forms.Timer based approach would be much appropriate for this concrete case. The "modern" approach would be based on async/await. If you need flexibility, the last one is the best choice. But whatever you choose, you'll hit a reentrancy problem at some point and will need to handle it. The best would be to prepare some helper utility class and use it from anywhere. Here is an example:
using System;
using System.Drawing;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace Tests
{
static class Program
{
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new TestForm());
}
class TestForm : Form
{
public TestForm()
{
var label = new Label { Parent = this, AutoSize = true, Top = 8, Left = 8 };
animateHelper = new AnimateHelper(label);
int left = 8;
foreach (var action in (ButtonAction[])Enum.GetValues(typeof(ButtonAction)))
{
var button = new Button { Parent = this, AutoSize = true, Text = action.ToString(), Left = left };
button.Top = DisplayRectangle.Bottom - button.Height - 8;
button.Click += (sender, e) => Execute(action);
left += button.Width + 8;
}
}
protected override void Dispose(bool disposing)
{
if (disposing && animateHelper != null) animateHelper.Cancel();
base.Dispose(disposing);
}
enum ButtonAction { TypewriteText, RepeatText, Cancel }
private void Execute(ButtonAction action)
{
// the original question
switch (action)
{
case ButtonAction.TypewriteText:
TypewriteText("This is a typewriter text animantion test.");
break;
case ButtonAction.RepeatText:
RepeatText("This is a repeating text animantion test.");
break;
case ButtonAction.Cancel:
animateHelper.Cancel();
break;
}
}
AnimateHelper animateHelper;
void TypewriteText(string text)
{
animateHelper.Execute(async (output, ct) =>
{
bool clear = true;
try
{
if (string.IsNullOrEmpty(text)) return;
output.ForeColor = Color.Blue;
for (int length = 1; ; length++)
{
if (ct.IsCancellationRequested) return;
output.Text = text.Substring(0, length);
if (length == text.Length) break;
await Task.Delay(50, ct);
}
clear = false;
}
finally { if (clear) output.Text = string.Empty; }
});
}
void RepeatText(string text)
{
animateHelper.Execute(async (output, ct) =>
{
try
{
if (string.IsNullOrEmpty(text)) return;
output.ForeColor = Color.Red;
while (true)
{
for (int length = 1; length <= text.Length; length++)
{
if (ct.IsCancellationRequested) return;
output.Text = text.Substring(text.Length - length);
await Task.Delay(50, ct);
}
for (int pad = 1; pad < text.Length; pad++)
{
if (ct.IsCancellationRequested) return;
output.Text = new string(' ', pad) + text.Substring(0, text.Length - pad);
await Task.Delay(50, ct);
}
if (ct.IsCancellationRequested) return;
output.Text = string.Empty;
await Task.Delay(250, ct);
}
}
finally { output.Text = string.Empty; }
});
}
}
class AnimateHelper
{
Label output;
Task task;
CancellationTokenSource cts;
public AnimateHelper(Label output) { this.output = output; }
void Reset()
{
if (cts != null) { cts.Dispose(); cts = null; }
task = null;
}
public void Cancel() { DontCare(CancelAsync()); }
async Task CancelAsync()
{
if (task != null && !task.IsCompleted)
{
try { cts.Cancel(); } catch { }
try { await task; } catch { }
}
Reset();
}
public void Execute(Func<Label, CancellationToken, Task> action) { DontCare(ExecuteAsync(action)); }
async Task ExecuteAsync(Func<Label, CancellationToken, Task> action)
{
await CancelAsync();
cts = new CancellationTokenSource();
task = action(output, cts.Token);
try { await task; } catch { }
Reset();
}
// make compiler happy
static void DontCare(Task t) { }
}
}
}
Related
I have a project that without usign any form/button or nothing like that, connects with a Websocket and using async methods receives some message(on a form created by myself) that is supposed to appear on the top-right corner of the screen.
But this message can appear from time to time (2 or 3 minutes) on the screen if the websocket doesn't say that it must stop. And this message can be big enough, that in order to make it look better I make my message appear in more than one form.
It causes an impression that it's a notification. So my class that connects with the websocket and receives the message async, calls another class using a thread that is a controller. The purpose of the controller is from time to time, show that message in various new form() notifications and obviously don't do it if the websocket doesn't return any message.
But when i call the form.show the program stops working.
I've looked around stackoverflow already, but the ideas that i've found didn't seem to work.
Some say that I should use invoke, but it kept giving error saying that
"Invoke or BeginInvoke cannot be called on a control until the window handle has been created", tried to solve like this: C# calling form.show() from another thread but it didn't work.
Some said that I should use .showDialog instead of .show, but it doesn't appear to be good, because it waits the window to be closed to terminate the method and as I said I need to open more than one notification at the same time.
Some said that the form was open with .show, but it was open for a very little period of time. But i couldn't notice if that was the case and even if it was i couldn't solve it. Well, what matter is that i'm stuck and i don't know what to do more.
Edited with Code:
//Main
Application.Run(new SocketService());
//SocketService class
public SocketService()
{
alerta = null;
while (true)
{
try
{
//Console.WriteLine("Nome do Usúario:" + Environment.UserName);
Thread.Sleep(2000);
Connect("ws://192.168.120.38:9091").Wait();
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
}
}
public static async Task Connect(string uri)
{
ClientWebSocket webSocket = null;
try
{
webSocket = new ClientWebSocket();
await webSocket.ConnectAsync(new Uri(uri), CancellationToken.None);
await Login(webSocket);
}
catch (Exception ex)
{
throw ex;
}
finally
{
if (webSocket != null)
webSocket.Dispose();
lock (consoleLock)
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine("WebSocket closed.");
Console.ResetColor();
}
}
}
private static async Task Login(ClientWebSocket webSocket)
{
ArraySegment<Byte> buffer = new ArraySegment<byte>(encoder.GetBytes( "{\"event\":\"loginBrowser\",\"data\":{\"login\":\"000000003077\",\"data\":\"1\"}}"));
await webSocket.SendAsync(buffer, WebSocketMessageType.Text, true, CancellationToken.None);
if (webSocket.State == WebSocketState.Open)
{
if (ShowMessage.created != true)
{
var dummy = new Control(); // to initialize SynchronizationContext
_sync = SynchronizationContext.Current;
new Thread(ThreadProc).Start();
}
await Receive(webSocket);
}
}
private static async Task Receive(ClientWebSocket webSocket)
{
while (webSocket.State == WebSocketState.Open)
{
ArraySegment<Byte> buffer = new ArraySegment<byte>(new Byte[256]);
var result = await webSocket.ReceiveAsync(buffer, CancellationToken.None);
if (result.MessageType == WebSocketMessageType.Close)
{
await webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None);
}
else
{
if (result.EndOfMessage)
{
message += encoder.GetString(buffer.ToArray());
SendMessage(message);
}
else
{
message += encoder.GetString(buffer.ToArray());
}
}
}
}
public static void ShowFormFromAnotherThread(string text)
{
_sync.Post(SendOrPostCallback, text);
}
private static void SendOrPostCallback(object state)
{
var form = new Notification();
form.Text = (string)state;
form.Show();
}
private static void ThreadProc()
{
while (true)
{
Thread.Sleep(2000); // wait imitation
ShowFormFromAnotherThread("HI");
}
}
/*Notification is my form and depending on where I put this part:
var dummy = new Control(); // to initialize SynchronizationContext
_sync = SynchronizationContext.Current;
new Thread(ThreadProc).Start();
Or i doesn't call login or doesn't enter receive() method or the best case It receives the information
calls the threadProc and the ShowFormFromAnotherThread but doesn't enter SednOrPostCallBack*/
using System.Threading;
using System.Windows.Forms;
namespace ConsoleThreadSync
{
internal class Program
{
private static void Main(string[] args)
{
Application.Run(new App());
}
}
public class App : ApplicationContext
{
private readonly SynchronizationContext _sync;
public App()
{
var dummy = new Control(); // to initialize SynchronizationContext
_sync = SynchronizationContext.Current;
new Thread(ThreadProc).Start();
}
public void ShowFormFromAnotherThread(string text)
{
_sync.Post(SendOrPostCallback, text);
}
private void SendOrPostCallback(object state)
{
var form = new Form1();
form.Text = (string)state;
form.Show();
}
private void ThreadProc()
{
while (true)
{
Thread.Sleep(2000); // wait imitation
ShowFormFromAnotherThread("HI");
}
}
}
}
Try to call this:
var dummy = new Control(); // to initialize SynchronizationContext
_sync = SynchronizationContext.Current;
from a contructor SocketService() and not from async methods. This is an initialization code and it must call from main thread.
Okay, after reading a little bit more, the solution that kind worked out was this one, but the only way of using the
.show from the notifician is to use the Application.DoEvents and I've been warned from the sources that I've looked into
that this method should not be used, unless is the only option, because It can cause some problems with the Threads and other things.
So unless someone can give me another hint or clue about what to do, I have two options or use this method and try to fix some other bug
that It can cause or use the .showDialog because don't know why It works without any other problem, but to use .showDialog I've
to use another thread where I create and show the notification because if I don't do, the loop will stop at each iteration
in order to wait the .showDialog be closed. And as it isn't a problem I want to avoid using a lot of threads, because it can cause
another problem with the sync between them:
namespace ReiDoCSharp
{
class ShowMessage
{
private static RootObject alerta;
public static bool created;
private static int startPosition;
public static void setStartPosition(int start)
{
if (start < startPosition)
{
startPosition = start;
}
}
public RootObject getAlerta()
{
return ShowMessage.alerta;
}
public void setAlerta(RootObject root)
{
ShowMessage.alerta = root;
}
private static void DoWork()
{
while (true)
{
if (created != true)
{
created = true;
}
if (alerta != null)
{
string mensagem = "";
if ((alerta.data.Informacoes[1] != "") && (alerta.data.Informacoes[1] != null))
{
mensagem += alerta.data.Informacoes[1];
}
if ((alerta.data.Informacoes[0] != "") && (alerta.data.Informacoes[0] != null))
{
mensagem += alerta.data.Informacoes[0];
}
if (mensagem != "")
{
startPosition = 5;
string[] messages = mensagem.Split(new[] { "<br><br>" }, StringSplitOptions.None);
foreach (string message in messages)
{
Notification popup = new Notification();
popup.label1.Text = message;
popup.TopMost = true;
popup.Show();
Application.DoEvents();
/*Solution with the ShowDialog would be:
Task.Run(() => showNotification(message));
*/
}
}
}
Thread.Sleep(5000);
}
}
//Then I won't need to use Application.DoEvents, but would have to create more threads
private static Task showNotification(string message)
{
Notification popup = new Notification();
popup.label1.Text = message;
popup.TopMost = true;
popup.ShowDialog();
}
public static Task createPopupsAsync()
{
Task.Run(() => DoWork());
}
}
}
namespace ReiDoCSharp
{
class SocketService
{
private static object consoleLock = new object();
private const bool verbose = true;
private static readonly TimeSpan delay = TimeSpan.FromMilliseconds(3000);
private static UTF8Encoding encoder = new UTF8Encoding();
private static string message;
private static RootObject alerta;
public SocketService()
{
Begin();
}
public static void Begin()
{
alerta = null;
while (true)
{
try
{
Thread.Sleep(2000);
Connect("ws://192.168.120.38:9091").Wait();
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
}
}
public static async Task Connect(string uri)
{
ClientWebSocket webSocket = null;
try
{
webSocket = new ClientWebSocket();
await webSocket.ConnectAsync(new Uri(uri), CancellationToken.None);
await Login(webSocket);
}
catch (Exception ex)
{
throw ex;
}
finally
{
if (webSocket != null)
webSocket.Dispose();
lock (consoleLock)
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine("WebSocket closed.");
Console.ResetColor();
}
}
}
private static async Task Login(ClientWebSocket webSocket)
{
ArraySegment<Byte> buffer = new ArraySegment<byte>(encoder.GetBytes("{\"event\":\"loginBrowser\",\"data\":{\"OPERADOR\":\"000000003077\",\"NRORG\":\"1\"}}"));
await webSocket.SendAsync(buffer, WebSocketMessageType.Text, true, CancellationToken.None);
if (webSocket.State == WebSocketState.Open)
{
Task.Factory.StartNew(() => ShowMessage.createPopupsAsync());
await Receive(webSocket);
}
}
private static async Task Receive(ClientWebSocket webSocket)
{
while (webSocket.State == WebSocketState.Open)
{
ArraySegment<Byte> buffer = new ArraySegment<byte>(new Byte[256]);
var result = await webSocket.ReceiveAsync(buffer, CancellationToken.None);
if (result.MessageType == WebSocketMessageType.Close)
{
await webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None);
}
else
{
if (result.EndOfMessage)
{
message += encoder.GetString(buffer.ToArray());
SendMessage(message);
}
else
{
message += encoder.GetString(buffer.ToArray());
}
}
}
}
private static void LogStatus(bool receiving, byte[] buffer, int length, string assunto)
{
lock (consoleLock)
{
Console.ForegroundColor = receiving ? ConsoleColor.Green : ConsoleColor.Yellow;
if (verbose)
{
Console.WriteLine(encoder.GetString(buffer) + " " + assunto);
}
Console.ResetColor();
}
}
private static void SendMessage(string message)
{
message = message.Replace("event", "evento");
message = message.Replace("\0", "");
JavaScriptSerializer js = new JavaScriptSerializer();
RootObject mess = js.Deserialize<RootObject>(message);
if (mess.data.Informacoes[1] != "")
{
mess.data.Informacoes[1] += "<br>";
}
if (alerta == null)
{
alerta = mess;
}
else
{
if ((mess.data.Quantidade[0] != 0) && (mess.data.Quantidade == null))
{
if ((mess.data.Quantidade[0] == -1) && (mess.data.Informacoes[0] == ""))
{
alerta = null;
}
else
{
alerta = mess;
}
}
else if (mess.data.Quantidade[0] == 0)
{
alerta = null;
}
if ((mess.data.Quantidade[1] != 0) && (mess.data.Informacoes[1] != ""))
{
alerta = mess;
}
}
new ShowMessage().setAlerta(alerta);
message = "";
}
}
}
I have custom thread which parses WiFi networks and updates the UI (DataGridView and graphs). Here is the thread method:
private void RefreshThread()
{
var watch = Stopwatch.StartNew();
while (true)
{
UpdateAllNetworks();
UpdateAllInterferences();
UpdateAllColors();
switch (ActivePage)
{
case Page.Start:
break;
case Page.Networks:
this.Invoke((MethodInvoker)delegate
{
UpdateDataGridWithNetworks();
ClearGraphs();
Draw24GHzGraph();
DrawSignalsOverTimeGraph();
});
break;
case Page.Channels:
break;
case Page.Analyze:
break;
default:
break;
}
watch.Stop();
int elapsedMs = (int) watch.ElapsedMilliseconds;
if (elapsedMs < Constants.NetworksRefreshThreadInterval)
Thread.Sleep(Constants.NetworksRefreshThreadInterval - elapsedMs);
}
}
Custom DataGridView:
public class CustomDataGridView : DataGridView
{
...
protected override void OnCellClick(DataGridViewCellEventArgs e)
{
base.OnCellClick(e);
int Index = e.RowIndex;
if (Index != -1)
{
DataGridViewRow row = Rows[Index];
PrimaryKeyForSelectedRow = row.Cells[KeyName].Value.ToString();
}
}
}
The DataGridView is my custom DataGrid where I have a click event handler. I have observed that sometimes the event handler isn't called but in most cases it is.
What could be the problem? Is it related to multithreading or the event isn't queued?
Your code blocks main thread, use separate thread for your network details update. Here is quick sample how it done.
class Program
{
static void Main(string[] args)
{
var helper = new Looper(5000, YourMethod_RefreshThread);
helper.Start();
}
private static void YourMethod_RefreshThread()
{
Console.WriteLine(DateTime.Now);
}
}
public class Looper
{
private readonly Action _callback;
private readonly int _interval;
public Looper(int interval, Action callback)
{
if(interval <=0)
{
throw new ArgumentOutOfRangeException("interval");
}
if(callback == null)
{
throw new ArgumentNullException("callback");
}
_interval = interval;
_callback = callback;
}
private void Work()
{
var next = Environment.TickCount;
do
{
if (Environment.TickCount >= next)
{
_callback();
next = Environment.TickCount + _interval;
}
Thread.Sleep(_interval);
} while (IsRunning);
}
public void Start()
{
if (IsRunning)
{
return;
}
var thread = new Thread(Work);
thread.Start();
IsRunning = true;
}
public void Stop()
{
this.IsRunning = false;
}
public bool IsRunning { get; private set; }
This question already has answers here:
A pattern to pause/resume an async task?
(5 answers)
Closed 5 years ago.
I have a sample code, taken from MSDN, to which I would like implement the Pause / Resume functionality within while loop. Could anybody propose a solution / parern which would hande this?
private async void startButton_Click(object sender, RoutedEventArgs e)
{
resultsTextBox.Clear();
// Instantiate the CancellationTokenSource.
cts = new CancellationTokenSource();
try
{
await AccessTheWebAsync(cts.Token);
resultsTextBox.Text += "\r\nDownloads complete.";
}
catch (OperationCanceledException)
{
resultsTextBox.Text += "\r\nDownloads canceled.\r\n";
}
catch (Exception)
{
resultsTextBox.Text += "\r\nDownloads failed.\r\n";
}
cts = null;
}
private void cancelButton_Click(object sender, RoutedEventArgs e)
{
if (cts != null)
{
cts.Cancel();
}
}
async Task AccessTheWebAsync(CancellationToken ct)
{
HttpClient client = new HttpClient();
// Make a list of web addresses.
List<string> urlList = SetUpURLList();
// ***Create a query that, when executed, returns a collection of tasks.
IEnumerable<Task<int>> downloadTasksQuery =
from url in urlList select ProcessURL(url, client, ct);
// ***Use ToList to execute the query and start the tasks.
List<Task<int>> downloadTasks = downloadTasksQuery.ToList();
// ***Add a loop to process the tasks one at a time until none remain.
while (downloadTasks.Count > 0)
{
// Identify the first task that completes.
Task<int> firstFinishedTask = await Task.WhenAny(downloadTasks);
// ***Remove the selected task from the list so that you don't
// process it more than once.
downloadTasks.Remove(firstFinishedTask);
// Await the completed task.
int length = await firstFinishedTask;
resultsTextBox.Text += String.Format("\r\nLength of the download: {0}", length);
}
}
There is an MSDN article that solves this using a PauseToken (similar to a CancellationToken).
Here's the sample code from that article that demonstrates this concept:
namespace PauseTokenTestApp
{
public class PauseTokenSource
{
private volatile TaskCompletionSource<bool> m_paused;
internal static readonly Task s_completedTask = Task.FromResult(true);
public bool IsPaused
{
get { return m_paused != null; }
set
{
if (value)
{
Interlocked.CompareExchange(
ref m_paused, new TaskCompletionSource<bool>(), null);
}
else
{
while (true)
{
var tcs = m_paused;
if (tcs == null) return;
if (Interlocked.CompareExchange(ref m_paused, null, tcs) == tcs)
{
tcs.SetResult(true);
break;
}
}
}
}
}
public PauseToken Token { get { return new PauseToken(this); } }
internal Task WaitWhilePausedAsync()
{
var cur = m_paused;
return cur != null ? cur.Task : s_completedTask;
}
}
public struct PauseToken
{
private readonly PauseTokenSource m_source;
internal PauseToken(PauseTokenSource source) { m_source = source; }
public bool IsPaused { get { return m_source != null && m_source.IsPaused; } }
public Task WaitWhilePausedAsync()
{
return IsPaused ?
m_source.WaitWhilePausedAsync() :
PauseTokenSource.s_completedTask;
}
}
class Program
{
static void Main()
{
var pts = new PauseTokenSource();
Task.Run(() =>
{
while (true)
{
Console.ReadLine();
pts.IsPaused = !pts.IsPaused;
}
});
SomeMethodAsync(pts.Token).Wait();
}
public static async Task SomeMethodAsync(PauseToken pause)
{
for (int i = 0; i < 100; i++)
{
Console.WriteLine(i);
await Task.Delay(100);
await pause.WaitWhilePausedAsync();
}
}
}
}
I have a problem when i wait for a task after i have canceled it with the CancellationTokenSource. The cancel call does not interrupt the task. When i wait
for the task the main thread blocks because the task will be never interrupted.
Here is a short description my program:
A task increments a char variable (from 'A' to 'Z') and shows it on the GUI thread. In order to do this the task executes a delegate (this.invoke()) on the thread the control was created on.
As soon as i comment out the RefreshTextBox()-Function the cancel call works and the task will be interrupted. It seems as if the this.invoke() command prevents the task from interrupting.
I the code below i have also implemented the same functionality with normal threads. And then i works. Where is the difference between task implementation and thread implementation?
using System.Windows.Forms;
using System.Threading;
using System.Threading.Tasks;
public partial class frm_Main : Form
{
private delegate void dgt_StringHandler(string str_Value);
CancellationTokenSource _obj_Cts = null;
Thread _obj_Thread = null;
Task _obj_Task = null;
public frm_Main()
{
InitializeComponent();
}
private void CreateChar(ref char chr_Value)
{
int int_Value;
int_Value = (int)chr_Value;
int_Value++;
if (int_Value > 90 || int_Value < 65)
int_Value = 65;
chr_Value = (char)int_Value;
}
private void TestThread()
{
char chr_Value = '#';
bool bol_Stop = false;
while (!bol_Stop)
{
try
{
Thread.Sleep(300);
CreateChar(ref chr_Value);
RefreshTextBox(chr_Value.ToString());
}
catch (ThreadInterruptedException)
{
bol_Stop = true;
}
}
}
private void TestTask(object obj_TokenTmp)
{
char chr_Value = '#';
CancellationToken obj_Token = (CancellationToken)obj_TokenTmp;
while (!obj_Token.IsCancellationRequested)
{
Thread.Sleep(300);
CreateChar(ref chr_Value);
RefreshTextBox(chr_Value.ToString());
}
}
private void RefreshTextBox(string str_Value)
{
if (txt_Value.InvokeRequired)
{
dgt_StringHandler obj_StringHandler = new dgt_StringHandler(RefreshTextBox);
this.Invoke(obj_StringHandler, new object[] { str_Value });
}
else
{
txt_Value.Text = str_Value;
}
}
private void btn_StartStop_Click(object sender, EventArgs e)
{
if (_obj_Task == null && _obj_Thread == null)
{
if (opt_Task.Checked)
{
_obj_Cts = new CancellationTokenSource();
_obj_Task = new Task(new Action<object>(TestTask), _obj_Cts.Token, _obj_Cts.Token);
_obj_Task.Start();
}
else
{
_obj_Thread = new Thread(new ThreadStart(TestThread));
_obj_Thread.Start();
}
btn_StartStop.Text = "Stop";
}
else
{
if (_obj_Thread != null)
{
_obj_Thread.Interrupt();
_obj_Thread.Join();
_obj_Thread = null;
}
if (_obj_Task != null)
{
_obj_Cts.Cancel();
_obj_Task.Wait();
_obj_Task = null;
_obj_Cts = null;
}
btn_StartStop.Text = "Start";
}
}
}
These 2 pieces of the code together form a deadlock:
_obj_Cts.Cancel();
_obj_Task.Wait();
and
this.Invoke(obj_StringHandler, new object[] { str_Value });
You are calling Wait() on the main thread, and Invoke() needs to be handled by the main thread.
You can break the deadlock by using this.BeginInvoke(...) instead.
The Thread version uses Interrupt, a sledgehammer. So the thread won't try to call RefreshTextBox() after the stop signal.
Here is the adapted code. I now call BeginInvoke() instead of Invoke() as Henk Holterman has proposed. This works very fine and is the only right way to prevent a deadlock. There is also another case that must be considered. I have also a IAsyncResult object that is given through the BeginInvoke() call. This object I use to check whether the async call has already completed or not. If I wouldn't check it it could be that the GUI thread is not fast enough (for example a sleep statement somewhere in the GUI thread) to execute my delegate and cause of this my TestTask() method would always call BeginInvoke() although the GUI thread has not already completed the last delegate. The result would be that my GUI thread would block the application.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using System.Threading.Tasks;
namespace InvokeTest
{
public partial class frm_Main : Form
{
private delegate void dgt_StringHandler(string str_Value);
CancellationTokenSource _obj_Cts = null;
Thread _obj_Thread = null;
Task _obj_Task = null;
IAsyncResult _obj_Ar = null;
public frm_Main()
{
InitializeComponent();
}
private void CreateChar(ref char chr_Value)
{
int int_Value;
int_Value = (int)chr_Value;
int_Value++;
if (int_Value > 90 || int_Value < 65)
int_Value = 65;
chr_Value = (char)int_Value;
}
private void TestThread()
{
char chr_Value = '#';
bool bol_Stop = false;
while (!bol_Stop)
{
try
{
Thread.Sleep(1); // is needed for interrupting the thread
CreateChar(ref chr_Value);
RefreshTextBox(chr_Value.ToString());
}
catch (ThreadInterruptedException)
{
bol_Stop = true;
}
}
}
private void TestTask(object obj_TokenTmp)
{
char chr_Value = '#';
CancellationToken obj_Token = (CancellationToken)obj_TokenTmp;
while (!obj_Token.IsCancellationRequested)
{
CreateChar(ref chr_Value);
RefreshTextBox(chr_Value.ToString());
}
}
private void RefreshTextBox(string str_Value)
{
if (txt_Value.InvokeRequired)
{
if (_obj_Ar == null ||
_obj_Ar.IsCompleted)
{
dgt_StringHandler obj_StringHandler = new dgt_StringHandler(RefreshTextBox);
_obj_Ar = this.BeginInvoke(obj_StringHandler, new object[] { str_Value });
}
}
else
{
Thread.Sleep(200);
txt_Value.Text = str_Value;
}
}
private void btn_StartStop_Click(object sender, EventArgs e)
{
if (_obj_Task == null && _obj_Thread == null)
{
if (opt_Task.Checked)
{
_obj_Cts = new CancellationTokenSource();
_obj_Task = new Task(new Action<object>(TestTask), _obj_Cts.Token, _obj_Cts.Token);
_obj_Task.Start();
}
else
{
_obj_Thread = new Thread(new ThreadStart(TestThread));
_obj_Thread.Start();
}
btn_StartStop.Text = "Stop";
}
else
{
if (_obj_Thread != null)
{
_obj_Thread.Interrupt();
_obj_Thread.Join();
_obj_Thread = null;
}
if (_obj_Task != null)
{
_obj_Cts.Cancel();
_obj_Task.Wait();
_obj_Task = null;
_obj_Cts = null;
}
btn_StartStop.Text = "Start";
}
}
private void frm_Main_FormClosing(object sender, FormClosingEventArgs e)
{
if (_obj_Thread != null)
{
_obj_Thread.Interrupt();
_obj_Thread.Join();
}
if (_obj_Task != null)
{
_obj_Cts.Cancel();
_obj_Task.Wait();
}
}
}
}
I want to playback a sound file in two or three external sound cards at the same time and I think that using threads is the solution but I really didn't know how to use it in the playback code.
This is the event makes on button play:
public partial class PlaybackForm : Form
{
IWavePlayer waveOut;
string fileName = null;
WaveStream mainOutputStream;
WaveChannel32 volumeStream;
int _deviceNum;
int _deviceNum1;
Thread t1;
Thread t2;
public PlaybackForm(int deviceNum,int deviceNum1)
{
InitializeComponent();
_deviceNum = deviceNum;
_deviceNum1 = deviceNum1;
}
private void buttonPlay_Click(object sender, EventArgs e)
{
if (waveOut != null)
{
if (waveOut.PlaybackState == PlaybackState.Playing)
{
return;
}
else if (waveOut.PlaybackState == PlaybackState.Paused)
{
waveOut.Play();
return;
}
}
// we are in a stopped state
// TODO: only re-initialise if necessary
if (String.IsNullOrEmpty(fileName))
{
toolStripButtonOpenFile_Click(sender, e);
}
if (String.IsNullOrEmpty(fileName))
{
return;
}
try
{
CreateWaveOut();
}
catch (Exception driverCreateException)
{
MessageBox.Show(String.Format("{0}", driverCreateException.Message));
return;
}
mainOutputStream = CreateInputStream(fileName);
trackBarPosition.Maximum = (int)mainOutputStream.TotalTime.TotalSeconds;
labelTotalTime.Text = String.Format("{0:00}:{1:00}", (int)mainOutputStream.TotalTime.TotalMinutes,
mainOutputStream.TotalTime.Seconds);
trackBarPosition.TickFrequency = trackBarPosition.Maximum / 30;
try
{
waveOut.Init(mainOutputStream);
}
catch (Exception initException)
{
MessageBox.Show(String.Format("{0}", initException.Message), "Error Initializing Output");
return;
}
// not doing Volume on IWavePlayer any more
volumeStream.Volume = volumeSlider1.Volume;
waveOut.Play();
}
And this is how to create the waveout:
private void CreateWaveOut()
{
CloseWaveOut();
int latency = (int)comboBoxLatency.SelectedItem;
//if (radioButtonWaveOut.Checked)
{
//WaveCallbackInfo callbackInfo = checkBoxWaveOutWindow.Checked ?
WaveCallbackInfo callbackInfo = WaveCallbackInfo.FunctionCallback();
// WaveCallbackInfo callbackInfo = WaveCallbackInfo.FunctionCallback();
// WaveCallbackInfo.NewWindow(): WaveCallbackInfo.FunctionCallback();
WaveOut outputDevice = new WaveOut(callbackInfo);
outputDevice.DesiredLatency = latency;
outputDevice.DeviceNumber = _deviceNum;
waveOut = outputDevice;
}
}
I declared two deviceNum but until now I can playsound only in one device,that's why I want to use thread.
Can you help me please
Thank you in advance
Do something like that:
using System.Threading;
...
private void buttonPlay_Click(object sender, EventArgs e)
{
ThreadPool.QueueUserWorkItem(new WaitCallback(this.PlaySound), 1);
ThreadPool.QueueUserWorkItem(new WaitCallback(this.PlaySound), 2);
}
private void PlaySound(object obj)
{
int deviceNumber = (int)obj;
// Do the stuff you used to do in buttonPlay_Click
WaveOut myWaveOut = CreateWaveOut(deviceNumber);
...
}
private WaveOut CreateWaveOut(int deviceNumber)
{
...
WaveOut outputDevice = new WaveOut(callbackInfo);
outputDevice.DesiredLatency = latency;
outputDevice.DeviceNumber = _deviceNum;
return outputDevice;
}