Just have a problem here that I have no idea how to fix. I am doing a small project which involves a GUI and serial data. The GUI is being run by the main thread and since the data variables that hold my incoming serial data need to be updated continuously, these are being updated in a second thread. The problem is when I need to update some textboxes on the GUI, these need to be updated with data from the secondary thread and that is where my problem lies. I can't update them directly from the secondary thread and I have no idea how I would transfer data from my secondary thread and work out a system of updating them from main thread. I have put my code below:
Any help would be great.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.IO;
using System.IO.Ports;
using System.Threading;
namespace GUIBike
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public static string inputdata;
public static int MaximumSpeed, maximumRiderInput, RiderInput, Time, CurrentSpeed, DistanceTravelled, MaximumMotorOutput, MotorOutput, InputSpeed;
public static string SaveDataString;
public Thread Serial;
public static SerialPort SerialData;
public static string[] portlist = SerialPort.GetPortNames();
public static string[] SaveData = new string[4];
public static string directory = "C:\\";
public MainWindow()
{
Serial = new Thread(ReadData);
InitializeComponent();
int Count = 0;
for (Count = 0; Count < portlist.Length; Count++)
{
ComPortCombo.Items.Add(portlist[Count]);
}
}
private void StartDataButton_Click(object sender, RoutedEventArgs e)
{
SerialData = new SerialPort(ComPortCombo.Text, 19200, Parity.None, 8, StopBits.One);
SerialData.Open();
SerialData.WriteLine("P");
Serial.Start();
StartDataButton.IsEnabled = false;
EndDataButton.IsEnabled = true;
ComPortCombo.IsEnabled = false;
CurrentSpeed = 0;
MaximumSpeed = 0;
Time = 0;
DistanceTravelled = 0;
MotorOutput = 0;
RiderInput = 0;
SaveData[0] = "";
SaveData[1] = "";
SaveData[2] = "";
SaveData[3] = "";
SaveDataButton.IsEnabled = false;
if (SerialData.IsOpen)
{
ComPortStatusLabel.Content = "OPEN";
SerialData.NewLine = "/n";
SerialData.WriteLine("0");
SerialData.WriteLine("/n");
}
}
private void EndDataButton_Click(object sender, RoutedEventArgs e)
{
SerialData.Close();
SaveDataButton.IsEnabled = true;
SerialData.WriteLine("1");
SerialData.WriteLine("0");
if (!SerialData.IsOpen)
{
ComPortStatusLabel.Content = "CLOSED";
}
int i = 0;
for (i = 0; i < 4; i++)
{
if (i == 0)
{
SaveDataString = "MaximumSpeed during the Ride was = " + Convert.ToString(MaximumSpeed) + "m/h";
SaveData[i] = SaveDataString;
}
if (i == 1)
{
SaveDataString = "Total Distance Travelled = " + Convert.ToString(DistanceTravelled) + "m";
SaveData[i] = SaveDataString;
}
if (i == 2)
{
SaveDataString = "Maximum Rider Input Power = " + Convert.ToString(maximumRiderInput) + "Watts";
SaveData[i] = SaveDataString;
}
if (i == 3)
{
SaveDataString = "Maximum Motor Output Power = " + Convert.ToString(MaximumMotorOutput) + "Watts";
SaveData[i] = SaveDataString;
}
}
}
private void SaveDataButton_Click(object sender, RoutedEventArgs e)
{
//File.WriteAllBytes(directory + "image" + imageNO + ".txt", ); //saves the file to Disk
File.WriteAllLines(directory + "BikeData.txt", SaveData);
}
public void ReadData()
{
int counter = 0;
while (SerialData.IsOpen)
{
if (counter == 0)
{
//try
//{
InputSpeed = Convert.ToInt16(SerialData.ReadChar());
CurrentSpeed = InputSpeed;
if (CurrentSpeed > MaximumSpeed)
{
MaximumSpeed = CurrentSpeed;
}
SpeedTextBox.Text = "Current Wheel Speed = " + Convert.ToString(CurrentSpeed) + "Km/h";
DistanceTravelled = DistanceTravelled + (Convert.ToInt16(CurrentSpeed) * Time);
DistanceTravelledTextBox.Text = "Total Distance Travelled = " + Convert.ToString(DistanceTravelled) + "Km";
//}
//catch (Exception) { }
}
if (counter == 1)
{
try
{
RiderInput = Convert.ToInt16(SerialData.ReadLine());
if (RiderInput > maximumRiderInput)
{
maximumRiderInput = RiderInput;
}
RiderInputTextBox.Text = "Current Rider Input Power =" + Convert.ToString(RiderInput) + "Watts";
}
catch (Exception) { }
}
if (counter == 2)
{
try
{
MotorOutput = Convert.ToInt16(SerialData.ReadLine());
if (MotorOutput > MaximumMotorOutput)
{
MaximumMotorOutput = MotorOutput;
}
MotorOutputTextBox.Text = "Current Motor Output = " + Convert.ToString(MotorOutput) + "Watts";
}
catch (Exception) { }
}
counter++;
if (counter == 3)
{
counter = 0;
}
}
}
private void ComPortCombo_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
StartDataButton.IsEnabled = true;
}
private void Window_Closed(object sender, RoutedEventArgs e)
{
if (SerialData.IsOpen)
{
SerialData.Close();
}
}
This question is related to
c#
multithreading
user-interface
sharing
You can use Dispatcher.Invoke to update your GUI from a secondary thread.
Here is an example:
private void Window_Loaded(object sender, RoutedEventArgs e)
{
new Thread(DoSomething).Start();
}
public void DoSomething()
{
for (int i = 0; i < 100000000; i++)
{
this.Dispatcher.Invoke(()=>{
textbox.Text=i.ToString();
});
}
}
You may use a delegate to solve this issue. Here is an example that is showing how to update a textBox using diffrent thread
public delegate void UpdateTextCallback(string message);
private void TestThread()
{
for (int i = 0; i <= 1000000000; i++)
{
Thread.Sleep(1000);
richTextBox1.Dispatcher.Invoke(
new UpdateTextCallback(this.UpdateText),
new object[] { i.ToString() }
);
}
}
private void UpdateText(string message)
{
richTextBox1.AppendText(message + "\n");
}
private void button1_Click(object sender, RoutedEventArgs e)
{
Thread test = new Thread(new ThreadStart(TestThread));
test.Start();
}
TestThread method is used by thread named test to update textBox
As akjoshi and Julio say this is about dispatching an Action to update the GUI on the same thread as the GUI item but from the method that is handling the background data. You can see this code in specific form in akjoshi's answer above. This is a general version.
myTextBlock.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal,
new Action(delegate()
{
myTextBlock.Text = Convert.ToString(myDataObject.getMeData());
}));
The critical part is to call the dispatcher of your UI object - that ensures you have the correct thread.
From personal experience it seems much easier to create and use the Action inline like this. Declaring it at class level gave me lots of problems with static/non-static contexts.
Here is a full example that updates UI textboxes
<Window x:Class="WpfThreading.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfThreading"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="216.84">
<Grid Margin="0,0,2,0">
<Button Content="Button" HorizontalAlignment="Left" Margin="10,10,0,0"
VerticalAlignment="Top" Width="75" Click="Button_Click"/>
<TextBox HorizontalAlignment="Left" Margin="10,35,0,10" TextWrapping="Wrap" Name="mtextBox" Width="87" VerticalScrollBarVisibility="Auto"/>
<TextBox HorizontalAlignment="Left" Margin="111,35,0,10" TextWrapping="Wrap" x:Name="mtextBox2" Width="87" VerticalScrollBarVisibility="Auto"/>
</Grid></Window>
and in the code
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void Button_Click(object sender, RoutedEventArgs e)
{
new Thread(DoSomething).Start();
new Thread(DoSomething2).Start();
}
public void DoSomething()
{
for (int i = 0; i < 100; i++)
{
Dispatcher.BeginInvoke(new Action(() => {
mtextBox.Text += $"{i.ToString()}{Environment.NewLine}";
}), DispatcherPriority.SystemIdle);
Thread.Sleep(100);
}
}
public void DoSomething2()
{
for (int i = 100; i > 0; i--)
{
Dispatcher.BeginInvoke(new Action(() => {
mtextBox2.Text += $"{i.ToString()}{Environment.NewLine}";
}), DispatcherPriority.SystemIdle);
Thread.Sleep(100);
}
}
}
Use Following Method to Update GUI.
Public Void UpdateUI()
{
//Here update your label, button or any string related object.
//Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.Background, new ThreadStart(delegate { }));
Application.Current.Dispatcher.Invoke(DispatcherPriority.Background, new ThreadStart(delegate { }));
}
Keep it in Mind when you use this method at that time do not Update same object direct from dispatcher thread otherwise you get only that updated string and this method is helpless/useless. If still not working then Comment that line inside method and un-comment commented one both have nearly same effect just different way to access it.
there.
I am also developing a serial port testing tool using WPF, and I'd like to share some experience of mine.
I think you should refactor your source code according to MVVM design pattern.
At the beginning, I met the same problem as you met, and I solved it using this code:
new Thread(() =>
{
while (...)
{
SomeTextBox.Dispatcher.BeginInvoke((Action)(() => SomeTextBox.Text = ...));
}
}).Start();
This works, but is too ugly. I have no idea how to refactor it, until I saw this: http://www.codeproject.com/Articles/165368/WPF-MVVM-Quick-Start-Tutorial
This is a very kindly step-by-step MVVM tutorial for beginners. No shiny UI, no complex logic, only the basic of MVVM.
You need to use Dispatcher.BeginInvoke. I did not test it but you can check this link(this is the same link provided by Julio G) to have better understanding on how to update the UI controls from different thread. I have modified your ReadData() code
public void ReadData()
{
int counter = 0;
while (SerialData.IsOpen)
{
if (counter == 0)
{
//try
//{
InputSpeed = Convert.ToInt16(SerialData.ReadChar());
CurrentSpeed = InputSpeed;
if (CurrentSpeed > MaximumSpeed)
{
MaximumSpeed = CurrentSpeed;
}
SpeedTextBox.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal,
new Action(delegate() { SpeedTextBox.Text = "Current Wheel Speed = " + Convert.ToString(CurrentSpeed) + "Km/h"; });//update GUI from this thread
DistanceTravelled = DistanceTravelled + (Convert.ToInt16(CurrentSpeed) * Time);
DistanceTravelledTextBox.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal,
new Action(delegate() {DistanceTravelledTextBox.Text = "Total Distance Travelled = " + Convert.ToString(DistanceTravelled) + "Km"; });//update GUI from this thread
//}
//catch (Exception) { }
}
if (counter == 1)
{
try
{
RiderInput = Convert.ToInt16(SerialData.ReadLine());
if (RiderInput > maximumRiderInput)
{
maximumRiderInput = RiderInput;
}
RiderInputTextBox.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal,
new Action(delegate() { RiderInputTextBox.Text = "Current Rider Input Power =" + Convert.ToString(RiderInput) + "Watts"; });//update GUI from this thread
}
catch (Exception) { }
}
if (counter == 2)
{
try
{
MotorOutput = Convert.ToInt16(SerialData.ReadLine());
if (MotorOutput > MaximumMotorOutput)
{
MaximumMotorOutput = MotorOutput;
}
MotorOutputTextBox.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal,
new Action(delegate() { MotorOutputTextBox.Text = "Current Motor Output = " + Convert.ToString(MotorOutput) + "Watts"; });//update GUI from this thread
}
catch (Exception) { }
}
counter++;
if (counter == 3)
{
counter = 0;
}
}
}
You have a couple of options here, I think.
One would be to use a BackgroundWorker. This is a common helper for multithreading in applications. It exposes a DoWork event which is handled on a background thread from the Thread Pool and a RunWorkerCompleted event which is invoked back on the main thread when the background thread completes. It also has the benefit of try/catching the code running on the background thread so that an unhandled exception doesn't kill the application.
If you don't want to go that route, you can use the WPF dispatcher object to invoke an action to update the GUI back onto the main thread. Random reference:
http://www.switchonthecode.com/tutorials/working-with-the-wpf-dispatcher
There are many other options around too, but these are the two most common that come to mind.
Source: Stackoverflow.com