I have an integer array declared in a class. Using that array, a PolyLine is drawn on a grid. The elements of the array are the y-coordinates. The array has to updated continuously and then the values are to be displayed. My idea of implementing this is to have two threads. One to update the values of the array and the other to print PolyLine on the grid.
Updating the array is not a problem. When I try to print PolyLine on the grid using the code below, an exception is thrown with the following message: "The calling thread cannot access this object because a different thread owns it."
Kindly suggest a workaround for this problem using thread. Perhaps, an event may be used instead of thread? I am open to suggestions. Any help is appreciated!
public partial class MainWindow : Window
{
Polyline Wave = new Polyline();
public MainWindow()
{
InitializeComponent();
Refresh();
DisplyOnGrid();
ThreadStart child = new ThreadStart(DisplyOnGrid);
Thread _DisplayOnGrid = new Thread(child);
_DisplayOnGrid.Priority = ThreadPriority.Highest;
_DisplayOnGrid.Start();
}
private void DisplyOnGrid()
{
Wave.Stroke = Brushes.Yellow;
Wave.StrokeThickness = 1.25;
for (int i = 0; i < DisplayGrid.Width; i++)
{
Wave.Points.Add(new Point(i, 50));
}
DisplayGrid.Children.Add(Wave);
}
private void Refresh()
{
DisplayGrid.Children.Clear();
}
}
You are getting Error because you are trying to access object which is owned by UI/Dispatcher thread
try something like this:
private void DisplyOnGrid()
{
Dispatcher.Invoke(new Action(()=>
{
Wave.Stroke = Brushes.Yellow;
Wave.StrokeThickness = 1.25;
for (int i = 0; i < DisplayGrid.Width; i++)
{
Wave.Points.Add(new Point(i, 50));
}
DisplayGrid.Children.Add(Wave);
}
))};
Related
I've got method which I'am calling from main thread. This method is creating a new thread. Code looks like this:
MouseCursorWallObject MouseCursorWall = null;
List<MovingRectangle> MovingRectangles = null;
DrawingImage RenderedImage;
public MainWindow()
{
InitializeComponent();
PrepareObjects();
GameLoopRun();
}
private void GameLoopRun()
{
Thread thread = new Thread(() =>
{
while (true)
{
DateTime dtStart = DateTime.Now;
Events();
Update();
Display();
DateTime dtEnd = DateTime.Now;
TimeSpan ts = dtEnd - dtStart;
if (SkipTicks - ts.TotalMilliseconds >= 0)
{
Thread.Sleep((int)(SkipTicks - ts.TotalMilliseconds));
}
}
});
thread.Start();
}
In Display() method i'am trying update Image control. "Display()" method looks like this:
private void Display()
{
DrawingGroup imageDrawings = new DrawingGroup();
// Drawing main canvas
imageDrawings.Children.Add(DrawingObject(500, 350, 0, 0, new Uri(#"Images\gameCanvas.jpg", UriKind.Relative)));
// Drawing mouse cursor wall
imageDrawings.Children.Add(DrawingObject(MouseCursorWall.Width, MouseCursorWall.Height, MouseCursorWall.GetLocX, MouseCursorWall.GetLocY, MouseCursorWall.DisplayTexture));
for (int i = 0; i < MovingRectangles.Count; i++)
{
MovingRectangle o = MovingRectangles[i];
// Drawing moving object
imageDrawings.Children.Add(DrawingObject(20, 20, o.GetLocX, o.GetLocY, o.TextureUri));
}
if (GamePause == true)
{
}
RenderedImage = new DrawingImage(imageDrawings);
// Image control on main UI thread
renderImage.Dispatcher.Invoke(() =>
{
renderImage.Source = RenderedImage;
});
}
The problem is when I'am trying update Image control using Dispatcher.Invoke I'am receiving error "The calling thread cannot access this object because a different thread owns it". I was trying a lot of different options, and only one works fine:
private void Display()
{
this.Dispatcher.Invoke(() => {
DrawingGroup imageDrawings = new DrawingGroup();
// Drawing main canvas
imageDrawings.Children.Add(DrawingObject(500, 350, 0, 0, new Uri(#"Images\gameCanvas.jpg", UriKind.Relative)));
// Drawing mouse cursor wall
imageDrawings.Children.Add(DrawingObject(MouseCursorWall.Width, MouseCursorWall.Height, MouseCursorWall.GetLocX, MouseCursorWall.GetLocY, MouseCursorWall.DisplayTexture));
for (int i = 0; i < MovingRectangles.Count; i++)
{
MovingRectangle o = MovingRectangles[i];
// Drawing moving object
imageDrawings.Children.Add(DrawingObject(20, 20, o.GetLocX, o.GetLocY, o.TextureUri));
}
if (GamePause == true)
{
}
RenderedImage = new DrawingImage(imageDrawings);
renderImage.Source = RenderedImage;
});
}
Could You explain me why second option of "Display()" method works fine, but the first one throwing exception? What I'am doing wrong?
Both the DrawingImage and the DrawingGroup inherit from DispatcherObject, which means that they need to be accessed from the thread on which they were created. That is why your version where all of the work is invoked back to the dispatcher works correctly.
As pointed out by Brian Reichle, these object also inherit from System.Windows.Freezable, which you can leverage to allow cross thread access to the objects.
I am trying to use Dynamic Data Display for my senior design project, but I'm having difficulty.
I can create the graph just fine, but I can't the line to update at all unless I am zooming in and out.
In most examples, all they had to do was create the graph, then when they manipulate the data, the graph updates itself.
So here are the main functions I am using with regards to the charts:
private List<WindDAQ.WindDataPoint> Chart1Data;
private EnumerableDataSource<WindDAQ.WindDataPoint> Chart1DataSource;
private void InitializeCharts()
{
Chart1Data = new List<WindDAQ.WindDataPoint>();
Chart1DataSource = new EnumerableDataSource<WindDAQ.WindDataPoint>(Chart1Data);
Chart1DataSource.SetXMapping(x => Chart1XAxis.ConvertToDouble(x.Time));
Chart1DataSource.SetYMapping(y => Chart1XAxis.ConvertToDouble(y.Lift));
Chart1.AddLineGraph(Chart1DataSource, Colors.Blue, 2, "Lift");
Chart1.Viewport.AutoFitToView = true;
}
private void UpdateChart()
{
for (int i = 0, count = itsDAQ.getStreamCount(); i < count; i++)
{
Chart1Data.Add(itsDAQ.getValue());
if(Chart1Data.Count >= 300)
{ Chart1Data.RemoveAt(0); }
}
}
InitializeCharts() is called once when creating the window.
UpdateChart() is called on a timer event.
WindDAQ.WindDataPoint contains Lift, Drag, Velocity, and Time data. Lift and Time are shown selected.
you should use the AppendAsync method of your observableCollection.
You'r updating only the list used to create the observable one, not the source of your graph.
private void UpdateChart()
{
for (int i = 0, count = itsDAQ.getStreamCount(); i < count; i++)
{
Chart1DataSource.AppendAsync(itsDAQ.getValue());
if (Chart1DataSource.Collection.Count >= 300) // this part should work in a thread-safe
{
Chart1DataSource.Collection.RemoveAt(0); // context and with some precaution
}
}
}
hope some of you can help me.
I have one PictureBox Array to show into an MdiChildForm just after it's showed.
But when I run the program, in the "CreatePictureBox" Method, which I execute only after I show the form I get a NullReferenceException. Why?
Here's the code of FormShowing
private void packOpeningToolStripMenuItem_Click(object sender, EventArgs e)
{
ProvaPackOpening ProvaPackOpening = new ProvaPackOpening();
ProvaPackOpening.MdiParent = this;
ProvaPackOpening.Show();
ProvaPackOpening.CreatePictureBox();
}
And that's the code of the array creation
public void CreatePictureBox()
{
Int16 i = 0;
PictureBox[] PicBoxArray = new PictureBox[10];
while (i < PicBoxArray.Count())
{
PicBoxArray[i].BackgroundImageLayout = ImageLayout.Center;
PicBoxArray[i].Location = new Point(0, 0);
PicBoxArray[i].Size = new Size(128, 185);
PicBoxArray[i].BackColor = Color.Aqua;
PicBoxArray[i].Parent = this.panBox;
PicBoxArray[i].Visible = true;
panBox.Controls.Add(PicBoxArray[i]);
PicBoxArray[i].Show();
i++;
}
}
I've thought about manage the whole program (it would be a game) with threads, but if there's some easier solution, it will be better.
When you create an array of objects, you're only allocating the space for the list of objects. You aren't creating the individual objects themselves. Add this line as the first line inside your while loop:
PicBoxArray[i] = new PictureBox();
I have an array of five threads. Each thread contains the same form, each form is put on to the screen in a different location (still working on that method :P).
I am trying to have each form load its contents (an image) before the other forms have finishing being placed. At the moment this works for the first form, but the others are blank or disappear :P
Originally each form would be placed but the method would need to finish before all the forms contents were displayed.
Any help would be appreciated, thanks :)
public partial class TrollFrm : Form
{
int number = 0;
public TrollFrm()
{
InitializeComponent();
startThreads();
}
private void TrollFrm_Load(object sender, EventArgs e)
{
}
private void TrollFrm_FormClosing(object sender, FormClosingEventArgs e)
{
e.Cancel = true;
}
public void startThreads()
{
Thread[] ThreadArray = new Thread[5];
for (int i = 0; i < 5; i++)
{
ThreadArray[i] = new Thread(new ThreadStart(createForm));
ThreadArray[i].Start();
}
}
public void createForm()
{
Form frm = new TrollChildFrm();
Random randomX = new Random();
Random randomY = new Random();
number++;
int xValue;
int yValue;
if (number % 2 == 0) //number is even.
{
xValue = (Convert.ToInt32(randomX.Next(1, 1920))) + 200;
yValue = (Convert.ToInt32(randomY.Next(1, 1080))) - 200;
}
else //number is not even.
{
xValue = (Convert.ToInt32(randomX.Next(1, 1920))) - 200;
yValue = (Convert.ToInt32(randomY.Next(1, 1080))) + 200;
}
frm.Show();
frm.Location = new Point(xValue, yValue);
Thread.Sleep(1000);
}
Your forms are not displaying correctly because they are not running on a thread with a message loop. The general rule is that all UI element accesses must occur on the main UI thread.
Since you have a call to Thread.Sleep(1000) I am going to assume that you want to wait 1 second between the initial display of each form. In that case I would use a System.Windows.Forms.Timer who's Tick event will call createForm directly. Enable the timer, let 5 Tick events come through, and then disable the timer. I see no need to create any threads at all.
The reason your forms aren't displaying is because you are running inside one method on the main UI thread. Instead, you could create a method that spawns a new form and launch that at certain intervals on another thread (making sure the form handling is done on the main UI thread). So you could do something like:
(Pseudo Code)
private const int TIME_THRESHOLD = 100;
int mElapsedTime = 0;
Timer mTimer = new Timer();
.ctor
{
mTimer.Elapsed += mTimer_Elapsed;
}
private void mTimer_Elapsed(...)
{
mElapsedTime++;
if (mElapsedTime >= TIME_THRESHOLD)
{
mElapsedTime = 0;
SpawnForm();
}
}
private void SpawnForm()
{
// Make sure your running on the UI thread
if (this.InvokeRequired)
{
this.BeginInvoke(new Action(SpawnForm));
return;
}
// ... spawn the form ...
}
This is just an example of what I was proposing - it would not look exactly like this in the code, but this should give you an idea of the execution steps.
I would suggest to use Thread.Sleep(1000) in this manner
Caller section
for (int i = 0; i < 5; i++)
{
ThreadArray[i] = new Thread(new ThreadStart(createForm));
ThreadArray[i].Start();
}
Thread.Sleep(1000);
Also in the method that executing the work for the thread.
while(!something)
{
Thread.Sleep(1000)
}
when user clicks on one of the available items (modules) available in his list I will use following code to create a new instance of selected item (user control) and then add it to my tabGroupArea .
object uc = Activator.CreateInstance(Type.GetType("myNamespace." + selectedItem.Parameter1Value), selectedItem);
Infragistics.Windows.DockManager.ContentPane contentPane = new Infragistics.Windows.DockManager.ContentPane();
contentPane.Content = uc;
tabGroupArea.Items.Add(contentPane);
the problem that I have is when the selectedItem has usercontrols inside it initializeComponent() will take a while to complete meanwhile the application will freeze and user can't do any thing ,I tried different ways to put
object uc = Activator.CreateInstance(Type.GetType("myNamespace." + selectedItem.Parameter1Value), selectedItem);
in a separate thread (Backgroundworker,thread and delegate) so I would be able to show user a loadin page .but I couldn't find anyway to do that .
any help would be appreciated .
thanks.
See this blog post.
Catel uses this approach for the PleaseWaitWindow.
the code below does it:
public partial class Window1 : Window
{
public delegate void CreateCanvasHandler(Grid parent, int index);
public Window1()
{
InitializeComponent();
int count = 10000;
this.TestCreateAsync(count);
}
private void TestCreateAsync(int count)
{
for (int i = 0; i < count; i++)
{
//check the DispatecherOperation status
this.LayoutRoot.Dispatcher.BeginInvoke(new CreateCanvasHandler(this.CreateCanvas),
DispatcherPriority.Background,
new object[2]
{
this.LayoutRoot,
i
});
}
}
private void CreateCanvas(Grid parent,
int index)
{
Canvas canvas = new Canvas()
{
Width = 200,
Height = 100
};
canvas.Children.Add(new TextBlock()
{
Text = index.ToString(),
FontSize = 14,
Foreground = Brushes.Black
});
Thread.Sleep(100);
parent.Children.Add(canvas);
}
}