In WPF, When I load a wrap panel with a lot of elements, the window stalls for a while before showing the content. I would like to add a wait hint but I could not find a way to detect when the wrap panel completes rendering.
I have tried "loaded", "sizechanged", "initialized" without success. Has anyone got any idea on this issue ?
Many thanks !
At the start of rendering call Dispatcher.BeginInvoke with the Dispatcher Priority of ContextIdle.
My start of rendering just happened to be a treeview selected item change event, but this could be any event that you need to wait for the UI to finish updating.
private void TreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
Dispatcher.BeginInvoke(new Action(() => DoSomething()), DispatcherPriority.ContextIdle, null);
}
private void DoSomething()
{
//This will get called after the UI is complete rendering
}
Yes, use the Window.ContentRendered event.
You can override the OnRender method to detect when rendering is complete.
To push all events call Dispatcher.DoEvents() where DoEvents is implemented as an extension method:
public static class DispatcherExtensions
{
public static void DoEvents(this Dispatcher dispatcher, DispatcherPriority priority = DispatcherPriority.Background)
{
DispatcherFrame frame = new DispatcherFrame();
DispatcherOperation dispatcherOperation = dispatcher.BeginInvoke(priority, (Action<DispatcherFrame>)ExitFrame, frame);
Dispatcher.PushFrame(frame);
if (dispatcherOperation.Status != DispatcherOperationStatus.Completed)
dispatcherOperation.Abort();
}
private static void ExitFrame(DispatcherFrame frame)
{
frame.Continue = false;
}
public static void Flush(this Dispatcher dispatcher, DispatcherPriority priority)
{
dispatcher.Invoke(()=> { }, priority);
}
}
In retrospect I think it's a terrible idea to use this because it can cause hard to solve bugs.
// this shows how bad it is to call Flush or DoEvents
int clicker = 0;
private void OnClick(object sender, RoutedEventArgs e)
{
if (clicker != 0)
{
// This is reachable... // Could be skipped for DispatcherPriority.Render but then again for render it seems to freeze sometimes.
}
clicker++;
Thread.Sleep(100);
this.Dispatcher.Flush(DispatcherPriority.Input);
//this.Dispatcher.DoEvents(DispatcherPriority.Render);
//this.Dispatcher.DoEvents(DispatcherPriority.Loaded);
//this.Dispatcher.DoEvents(DispatcherPriority.Input);
//this.Dispatcher.DoEvents(DispatcherPriority.Background);
clicker--;
}
Related
I need my WPF exe to start monitoring a queue as soon as it starts up, and then respond to messages as they come in.
The way I have it now is:
public partial class App
{
readonly BackgroundWorker _worker = new BackgroundWorker();
protected override void OnStartup(StartupEventArgs e)
{
_worker.DoWork += worker_DoWork;
_worker.RunWorkerCompleted += worker_RunWorkerCompleted;
_worker.RunWorkerAsync();
}
void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
_worker.DoWork += worker_DoWork;
_worker.RunWorkerAsync();
}
static void worker_DoWork(object sender, DoWorkEventArgs e)
{
//do work
}
Obviously, this is pretty pathetic IMO.
Also, I don't like the approach of using while(true), inside the thread to keep it running indefinitely..
It's enough to read the messages from queue not permanently but periodically.
The common approach for this is using timer. For example, System.Threading.Timer.
public partial class App : Application
{
private System.Threading.Timer _msmqReadTimer;
public App()
{
_msmqReadTimer = new System.Threading.Timer(MsmqReadTimerTick);
_msmqReadTimer.Change(0, 1000); // call MsmqReadTimerTick immediatelly and each 1000 ms
}
private void MsmqReadTimerTick(object state)
{
// do work
// if you want to update some UI components after work, you should post this to UI thread dispatcher:
this.Dispatcher.Invoke(()=>
{
// logic for updating UI should be here
},
System.Windows.Threading.DispatcherPriority.Background);
}
}
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
Thread HeartRateThread = new Thread(startThread);
HeartRateThread.Name = "Class1";
HeartRateThread.Start();
}
private void startThread(object obj)
{
new Class1();
}
}
public class Class1
{
public Class1()
{
DispatcherTimer timer1 = new DispatcherTimer();
timer1.Interval = new TimeSpan(0,0,0,1);
timer1.Tick += timer1_tick;
timer1.Start();
}
private void timer1_tick(object sender, EventArgs e)
{
Debug.WriteLine("timer called");
}
}
I am trying to enable this timer_tick function fromanother thread as it is obvious in the code section of maInWindow. However, the Class1 constructor is called but timertick functin is not enabled. However if i do this on the main thread, everything works fine. Any reason for this.And how can I get it working?
DispatcherTimer can only work run on a UI thread. However, in your case you are creating a DispatcherTimer on a background thread. DispatcherTimer, internally tries to get Dispatcher.CurrentDispatcher, in your case it gets dispatcher for the background thread, not for the main UI thread.
Do you really need DispatcherTimer? If you are not going to manipulate any UI elements in the timer1_tick method, then you are better off to go with a different timer, like System.Timers.Timer.
Refer to this to read more about available Timers in .net.
Maybe you can try something like this:
private void timer1_tick(object sender, EventArgs e)
{
Application.Current.Dispatcher.BeginInvoke(new Action(() => Debug.WriteLine("timer called")));
}
Without having tested it, I guess you have to pass the MainWindow's Dispatcher to the DispatcherTimer on construction. Otherwise it will create its own:
private void startThread(object obj)
{
new Class1(Dispatcher);
}
...
public Class1(Dispatcher dispatcher)
{
DispatcherTimer timer1 =
new DispatcherTimer(DispatcherPriority.Background, dispatcher);
timer1.Interval = new TimeSpan(0,0,0,1);
timer1.Tick += timer1_tick;
timer1.Start();
}
you can use Dispatcher for call startThread method.
object objParameter = "parametervalue";
Application.Current.Dispatcher.BeginInvoke(DispatcherPriority.Background, new Action(
() => startThread(objParameter)));
I have a WPF window with a button that spawns a BackgroundWorker thread to create and send an email. While this BackgroundWorker is running, I want to display a user control that displays some message followed by an animated "...". That animation is run by a timer inside the user control.
Even though my mail sending code is on a BackgroundWorker, the timer in the user control never gets called (well, it does but only when the Backgroundworker is finished, which kinda defeats the purpose...).
Relevant code in the WPF window:
private void button_Send_Click(object sender, RoutedEventArgs e)
{
busyLabel.Show(); // this should start the animation timer inside the user control
BackgroundWorker worker = new BackgroundWorker();
worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
worker.DoWork += new DoWorkEventHandler(worker_DoWork);
worker.RunWorkerAsync();
}
void worker_DoWork(object sender, DoWorkEventArgs e)
{
this.Dispatcher.Invoke((Action)(() =>
{
string body = textBox_Details.Text;
body += "User-added addtional information:" + textBox_AdditionalInfo.Text;
var smtp = new SmtpClient
{
...
};
using (var message = new MailMessage(fromAddress, toAddress)
{
Subject = subject,
Body = body
})
{
smtp.Send(message);
}
}));
}
Relevant code in the user control ("BusyLabel"):
public void Show()
{
tb_Message.Text = Message;
mTimer = new System.Timers.Timer();
mTimer.Interval = Interval;
mTimer.Elapsed += new ElapsedEventHandler(mTimer_Elapsed);
mTimer.Start();
}
void mTimer_Elapsed(object sender, ElapsedEventArgs e)
{
this.Dispatcher.Invoke((Action)(() =>
{
int numPeriods = tb_Message.Text.Count(f => f == '.');
if (numPeriods >= NumPeriods)
{
tb_Message.Text = Message;
}
else
{
tb_Message.Text += '.';
}
}));
}
public void Hide()
{
mTimer.Stop();
}
Any ideas why it's locking up?
Using Dispatcher.Invoke in your worker_DoWork method is putting execution back on the UI thread, so you are not really doing the work asynchronously.
You should be able to just remove that, based on the code you are showing.
If there are result values that you need to show after the work is complete, put it in the DoWorkEventArgs and you will be able to access it (on the UI thread) in the worker_RunWorkerCompleted handler's event args.
A primary reason for using BackgroundWorker is that the marshalling is handled under the covers, so you shouldn't have to use Dispatcher.Invoke.
I have developed an interesting WPF control that is currently slowing down my entire application :) On my custom control, I have an image control that I need to update everytime a backend event occurs. This backend event is firing twice a second (very fast). When the event fires I need to pull a Bitmap object out of a 3rd party control, convert to a BitmapSource object and then bind it to my Image control. Each time my event is fired, I am queuing a new work item in the ThreadPool. The item will then fetch the Bitmap and do the conversion in a background worker object. This is done everytime the event fires. I am using the dispatcher to update my image control source with BeginInvoke but I still get an unresponsive app. Please let me know what I can do to make this process better performing and help to make my app more responsive:
Here is the code in my event:
void inSight_ResultsChanged(object sender, EventArgs e)
{
ThreadPool.QueueUserWorkItem(new WaitCallback(ProcessEvent), ((InSightViewer)this.DataContext).CvsDisplay);
}
Here is the code from delegate:
void ProcessEvent(object display)
{
BackgroundWorker bw = new BackgroundWorker();
bw.DoWork += new DoWorkEventHandler(bw_DoWork);
bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
bw.RunWorkerAsync(display);
}
Here is the code in my background worker DoWork event:
void bw_DoWork(object sender, DoWorkEventArgs e)
{
3rdPartyControl displayControl = new 3rdPartyControl();
displayControl.ImageHost = (ImgHost)e.Argument;
Bitmap b = displayControl.GetBitmap();
var mBitmap = b.GetHbitmap();
BitmapSource bs;
try
{
bs = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(
mBitmap,
IntPtr.Zero,
Int32Rect.Empty,
BitmapSizeOptions.FromEmptyOptions());
bs.Freeze();
}
catch (System.Exception ex) { throw ex; }
finally
{
DeleteObject(mBitmap);
}
e.Result = bs;
}
Here is the code in RunWorkerCompleted event:
void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
Application.Current.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.ApplicationIdle, (ThreadStart)delegate()
{
this.imgSource.Source = (BitmapSource)e.Result;
});
}
void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
Application.Current.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.ApplicationIdle, (ThreadStart)delegate()
{
this.imgSource.Source = (BitmapSource)e.Result;
});
}
System.Windows.Threading.DispatcherPriority.ApplicationIdle means Operations are processed when the application is idle.
What if the application is always busy and never idle? The requests will be queued and the app slows down.
However I haven't tested this because I don't have the source code of your app.
I'm working on building a multi-threaded UI. I would like long processes to be handled by the BackgroundWorker class, and have a small timer on the UI to keep track of how long the process is taking. It's my first time building such a UI, so I'm reading up on related resources on the web. My test code is thus:
private BackgroundWorker worker;
private Stopwatch swatch = new Stopwatch();
private delegate void simpleDelegate();
System.Timers.Timer timer = new System.Timers.Timer(1000);
string lblHelpPrevText = "";
private void btnStart_Click(object sender, RoutedEventArgs e)
{
try
{
worker = new BackgroundWorker(); //Create new background worker thread
worker.DoWork += new DoWorkEventHandler(BG_test1);
worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(BG_test1end);
worker.RunWorkerAsync();
simpleDelegate del = new simpleDelegate(clockTicker);
AsyncCallback callBack = new AsyncCallback(clockEnd);
IAsyncResult ar = del.BeginInvoke(callBack, null);
lblHelpText.Text = "Processing...";
}
finally
{
worker.Dispose(); //clear resources
}
}
private void clockTicker()
{
//Grab Text
simpleDelegate delLblHelpText = delegate()
{ lblHelpPrevText = this.lblHelpText.Text; };
this.Dispatcher.BeginInvoke(DispatcherPriority.Send, delLblHelpText);
//Start clock
timer.Elapsed += new ElapsedEventHandler(clockTick);
timer.Enabled = true;
swatch.Start();
}
private void clockTick(object sender, ElapsedEventArgs e)
{
simpleDelegate delUpdateHelpTxt = delegate()
{ this.lblHelpText.Text = String.Format("({0:00}:{1:00}) {2}", swatch.Elapsed.Minutes, swatch.Elapsed.Seconds, lblHelpPrevText); };
this.Dispatcher.BeginInvoke(DispatcherPriority.Send, delUpdateHelpTxt);
}
private void BG_test1(object sender, DoWorkEventArgs e)
{
//this.lblHelpText.Text = "Processing for 10 seconds...";
Thread.Sleep(15000);
}
private void BG_test1end(object sender, RunWorkerCompletedEventArgs e)
{
this.lblHelpText.Text = "Process done.";
this.timer.Enabled = false;
this.swatch.Stop();
this.swatch.Reset();
}
static void clockEnd(IAsyncResult ar)
{
simpleDelegate X = (simpleDelegate)((AsyncResult)ar).AsyncDelegate;
X.EndInvoke(ar);
}
The idea is when the button is clicked, we take the status text from a Label (e.g. "Processing...") then append the time onto it every second. I could not access the UI elements from the Timer class as it's on a different thread, so I had to use delegates to get and set the text.
It works, but is there a better way to handle this? The code seems much for such a basic operation. I'm also not fully understanding the EndInvoke bit at the bottom. I obtained the snippet of code from this thread Should One Always Call EndInvoke a Delegate inside AsyncCallback?
I understand the idea of EndInvoke is to receive the result of BeginInvoke. But is this the correct way to use it in this situation? I'm simply worried about any resource leaks but when debugging the callback appears to execute before my timer starts working.
Don't use a separate timer to read the progress of your BackgroundWorker and update the UI. Instead, make the BackgroundWorker itself "publish" its progress to the UI directly or indirectly.
This can be done pretty much anyway you want to, but there's a built-in provision exactly for this case: the BackgroundWorker.ProgressChanged event.
private void BG_test1(object sender, DoWorkEventArgs e)
{
for(var i = 0; i < 15; ++i) {
Thread.Sleep(1000);
// you will need to get a ref to `worker`
// simplest would be to make it a field in your class
worker.ReportProgress(100 / 15 * (i + 1));
}
}
This way you can simply attach your own handler to ProgressChanged and update the UI using BeginInvoke from there. The timer and everything related to it can (and should) go.
You can use timer to update UI. It is normal practice. Just instead of System.Timer.Timer I suggest use System.Windows.Threading.DispatcherTimer. The DispatcherTimer runs on the same thread as the Dispatcher. Also, instead of BackgroundWorker you can use ThreadPool.
Here is my sample:
object syncObj = new object();
Stopwatch swatch = new Stopwatch();
DispatcherTimer updateTimer; // Assume timer was initialized in constructor.
void btnStart_Click(object sender, RoutedEventArgs e) {
lock (syncObj) {
ThreadPool.QueueUserWorkItem(MyAsyncRoutine);
swatch.Start();
updateTimer.Start();
}
}
void updateTimer_Tick(object sender, EventArgs e) {
// We can access UI elements from this place.
lblHelpText.Text = String.Format("({0:00}:{1:00}) Processing...", swatch.Elapsed.Minutes, swatch.Elapsed.Seconds);
}
void MyAsyncRoutine(object state) {
Thread.Sleep(5000);
lock (syncObj)
Dispatcher.Invoke(new Action(() => {
swatch.Stop();
updateTimer.Stop();
lblHelpText.Text = "Process done.";
}), null);
}
private void button1_Click(object sender, EventArgs e)
{
string strFullFilePath = #"D:\Print.pdf";
ProcessStartInfo ps = new ProcessStartInfo();
ps.UseShellExecute = true;
ps.Verb = "print";
ps.CreateNoWindow = true;
ps.WindowStyle = ProcessWindowStyle.Hidden;
ps.FileName = strFullFilePath;
Process.Start(ps);
Process proc = Process.Start(ps);
KillthisProcess("AcroRd32");
}
public void KillthisProcess(string name)
{
foreach (Process prntProcess in Process.GetProcesses())
{
if (prntProcess.ProcessName.StartsWith(name))
{
prntProcess.WaitForExit(10000);
prntProcess.Kill();
}
}
}