Here's the problem:
I have an Outlook add-in made with add-in express.
It hosts a panel with the only winforms ElementHost, where WPF content is performing.
In this WPF control I have a textbox and button.
Button click triggers Backgroundworker to load info from database, in 'RunWorkerCompleted' process this data is being put into control.
When button is pressed - everything goes normally. But if I catch 'Enter' key press in textbox and then trigger BackgroundWorker - 'RunWorkerCompleted' is being launched not in the main thread, but in a thread pool, and cannot access WPF elements.
In both cases BackGroundWorker.RunWorkerAsync() is being called from Main thread, DoWork runs in thread pool, and only in case of enter-key-catch, RunWorkerCompleted also runs in a thread pool.
You've run into a bug in Add-in Express. In some cases Add-in Express event handlers are called with System.Threading.SynchronizationContext.Current set to null. BackgroundWorker use it in RunWorkerAsync method to save the ui context, so that is the problem.
To fix SynchronizationContext you could use the following workaround. Here MyAction is the method where you call RunWorkerAsync from.
var ctx = SynchronizationContext.Current;
if (ctx != null)
{
MyAction();
}
else
{
var timer = new DispatcherTimer();
timer.Tick += (s, a) =>
{
MyAction();
timer.Stop();
timer = null;
};
timer.Interval = TimeSpan.FromMilliseconds(10);
timer.Start();
}
Another solution would be saving the valid SynchronizationContext.Current value somewhere in a static member and then calling SynchronizationContext.Post in the event handler for the same purpose. I haven't tried this one though.
Related
This question already has answers here:
How do I update the GUI from another thread?
(47 answers)
Closed 1 year ago.
Currently I am creating a background STA thread to keep the UI responsive but it slows down my function calls on the main thread.
Based on this thread How to update progress bar while working in the UI thread I tried the following but the UI only gets updated after all of the work has finished. I tried playing around with the Dispatcher priorities but none of them seem to work.
What I also tried is adding _frmPrg.Refresh() to my Progress callback but this does not seem to change anything.
Dim oProgress = New Progress(Of PrgObject)(Sub(runNumber)
_frmPrg.Invoke((Sub()
_frmPrg.Status = runNumber
End Sub))
End Sub)
System.Windows.Threading.Dispatcher.CurrentDispatcher.BeginInvoke(Sub()
DoLongRunningWork(oProgress, _cancellationToken)
End Sub, System.Windows.Threading.DispatcherPriority.Background)
I can't really help you with your problem, but I'll try to clarify what happens in your posted code.
DoLongRunningWork will be invoked through Dispatcher on the UI thread, when the UI thread is not busy. But once started, it will block the UI thread until it completes. So you can't show a progress this way. Your single chance is, to let DoLongRunningWork run on a background thread. That brings you nothing, if the long-running methods come from office objects, which must be accessed from the UI thread...
The Progress class (see the remarks section) invokes your event handler on the UI thread automatically, so you don't need _frmPrg.Invoke in your event handler.
Maybe you can start a STAthread for your progress form and show it from there. The instance of your Progress class must be created in this thread too, but not before your form is shown to ensure, that the thread becomes a WindowsFormsSynchronisationContext (or you set one explicitly after starting the thread). A plain SynchronisationContext won't work!
At least you get updates in your form this way, but the UI thread of the office app will still be blocked. And of course, any action you make with your progress form must be invoked on the UI thread, if accessing office objects.
After reading some other posts, I decided to suggest another solution. My previous answer still contains usable information, so I'll leave it there. I'm not familiar with VB.NET syntax, so the samples are in C#. I have tested the code in a VSTO plugin for PowerPoint, but it should run in any office application.
Forget the Progress class and background threads. Run everything on the UI thread!
Now use some async code. To stay on the UI thread, we need a "good" SynchronizationContext.
private static void EnsureWinFormsSyncContext()
{
// Ensure that we have a "good" SynchronisationContext
// See https://stackoverflow.com/a/32866156/10318835
if (SynchronizationContext.Current is not WindowsFormsSynchronizationContext)
SynchronizationContext.SetSynchronizationContext(new WindowsFormsSynchronizationContext());
}
This is the event handler of a button. Note the manually added async keyword. The SynchronizationContext.Current gets resetted again and again, so ensure the good one in the EventHandler:
private async void OnButtonClick(object sender, EventArgs e)
{
EnsureWinFormsSyncContext();
// Return from event handler, ensure that we are really async
// See https://stackoverflow.com/a/22645114/10318835
await Task.Yield();
await RunLongOnUIThread();
}
This will be the worker method, also running on the UI thread.
private async Task RunLongOnUIThread()
{
//Dummy code, replace it with your code
var pres = addIn.Application.Presentations.Add();
for (int i = 0; i < 100; i++)
{
Debug.Print("Creating slide {0} on thread {1}", i, Thread.CurrentThread.ManagedThreadId);
// If you have some workloads that can be run on a background
// thread, execute them with await Task.Run(...).
try
{
var layout = pres.Designs[1].SlideMaster.CustomLayouts[1];
var slide = pres.Slides.AddSlide(i + 1, layout);
var shape = slide.Shapes.AddLabel(Microsoft.Office.Core.MsoTextOrientation.msoTextOrientationHorizontal, 0, 15 * i, 100, 15);
shape.TextFrame.TextRange.Text = $"Text on slide {i + 1}";
}
catch (Exception ex)
{
Debug.Print("I don't know what am I doing here, I'm not familiar with PowerPoint... {0}", ex);
}
// Update UI
statusLabel.Text = $"Slide {i + 1} done";
progressBar1.Value = i + 1;
// This is the magic! It gives the main thread the opportunity to update the UI.
// It also processes input messages so you need to disable unwanted buttons etc.
await IdleYield();
}
}
The following method is for Windows Forms Applications where it does the job perfect. I've tried it also in PowerPoint. If you are facing problems, try the WPF flavour with await Dispatcher.Yield(DispatcherPriority.ApplicationIdle) instead of await IdleYield().
private static Task IdleYield()
{
var idleTcs = new TaskCompletionSource<bool>();
void handler(object s, EventArgs e)
{
Application.Idle -= handler;
idleTcs.SetResult(true);
}
Application.Idle += handler;
return idleTcs.Task;
}
Here are the (clickable) links to the answers that I used (I can't put them in the code-blocks...).
Incorrect async/await working, Excel events in Excel Application Level Add-in
When would I use Task.Yield()?
Task.Yield - real usages?
If in your real code something runs not as expected, check the thread you are running on and SynchronizationContext.Current.
I would like to create a custom FunctionPlotter component that is based on the JavaFx WebEngine. My plots will be shown in a browser. Before I execute my plot commands I have to wait until the browser has been initialized (it loads d3.js). Currently I do so by putting my plot expressions in a Runnable and pass that runnable to the FunctionPlotter. (The FunctionPlotter passes the runnable to the loading finished hook of the browser):
private FunctionPlotter plotter;
...
Runnable plotRunnable = ()->{
plotter.plot("x^2");
}
plotter = new FunctionPlotter(plotRunnable);
However I would prefer following (blocking) work flow for the usage of my FunctionPlotter component:
Functionplotter plotter = new FunctionPlotter();
plotter.plot("x^2")
=> The FunctionPlotter should automatically wait until the wrapped browser has been initialized.
How should I do this in an JavaFx Application?
Inside the FunctionPlotter I could do something like
private Boolean isInitialized = false
...
ReadOnlyObjectProperty<State> state = webEngine.getLoadWorker().stateProperty();
state.addListener((obs, oldState, newState) -> {
boolean isSucceeded = (newState == Worker.State.SUCCEEDED);
if (isSucceeded) {
isInitialized = true;
}
});
webEngine.loadContent(initialBrowserContent);
waitUntilInitialLoadingIsFinished();
My actual question is how the method on the last line could be implemented. If I use following code, the application will wait for ever:
private void waitUntilBrowserIsInitialized() {
while(!isInitialized){
try {
Thread.sleep(100);
} catch (InterruptedException e) {
}
}
}
I know that there is stuff like JavaFx Tasks, Platform.runLater(), Service, CountdownLatch (JavaFX working with threads and GUI) but those did not help me (= I did not get it working). How can I wait in the main Thread until a Runnable is finished?
Here someone says that the JavaFx Application thread should never be blocked:
Make JavaFX application thread wait for another Thread to finish
Any other suggestions?
Edit
Related question: JavaFX/SWT WebView synchronous loadcontent()
I decided to wrap the plot functionality in an internal queue of plot instructions. The command
plotter.plot("x^2");
will not actually execute the plot but add a plot instruction to the queue. After the browser has been initialized, that queue will be worked through and the plot commands will be executed with a delay. While the browser is initializing I will show some kind of progress bar.
If you know a solution that does not need this delayed execution work around please let me know.
I have a worker thread doing calculation on the background and I want to send a event/message to call a update function to update the graphics on screen once the worker thread finish calculation.
How do I do that in cocos2d ?
Some demo code:
-(void) updateGraphic
{
//this one update all the graphics/sprite
}
//note workerThreadFunc is being used to start a new thread
-(void) workerThreadFunc
{
//...
//...
//finish calculation here
//since it's in a different thread, I cannot call updateGraphic directly here
//So I need a event to notify update Graphic here somehow
}
Cocos2D calls the -(void) draw {} method on all nodes automatically on the main thread. You do not need to call that method from another thread, and you can not perform custom OpenGL drawing outside the draw method.
In order to call a method that should be performed on the main thread, use the performSelectorOnMainThread method.
I've achieve it via pthreads, it needs to do some changes in CCDirector.cpp & CCDirector.h
the details is in this thread.
to use it, we can register handleMessageInUI in UI thread, then worker thread sends a message to UI thread, which will call handleMessageInUI to do UI drawing. some sample code is below:
In UI thread, we can register a handler to process message in UI thread.
bool HelloWorldScene::handleMessageInUIThread(const EXTCCMessage &msg) {
// implementations
// return true if this handler has processed this msg,
// otherwise, false is returned
switch (msg.msgId) {
case 2:
break;
default:
return false;
}
return true;
}
// register this Handler to UI Threader
CCDirector::mainLoopHandler()->registerHandler(this, (EXTCCHandleMessage)&HelloWorldScene::handleMessageInUIThread);
send a message to UI thread in a worker thread
EXTCCMessage msg;
msg.msgId = 2;
msg.msgData1 = NULL;
// "msg" will be processed by "handleMessageInUIThread" in UI thread
CCDirector::mainLoopHandler()->postMessage(msg);
I am using LWUIT ResrouceEditor(latest SVN code revision 1513) to generate a UI State machine.
I want to show a wait screen when a long running command is invoked by a user using a button on the current form. I believe I can use the asynchronous option when linking the command on the button. I have setup a form in which I have a button which should invoke the asynchronous command. In command selection for that button, I have set the action to show the wait screen form and have marked the command as asynchronous. However when I use the asynchronous option, the code shows the wait screen, but after that it throws a NullPointerException.
As per my understanding, once you mark a command as asynchronous, it will call the following methods from a different thread where you can handle its processing.
protected void asyncCommandProcess(Command cmd, ActionEvent sourceEvent);
protected void postAsyncCommand(Command cmd, ActionEvent sourceEvent);
However this methods are not getting called and it throws a NullPointerException.
When I looked at the LWUIT code, in UIBuilder.java(lineno. 2278), I see that it constructs the new thread for an asynchronous command as follows:
new Thread(new FormListener(currentAction, currentActionEvent, f)).start();
But when running it through Debugger I see that currentAction and currentActionEvent are always null. And hence when the FormListener thread starts running, it never calls the above two async command processing methods. Please see the listing of the run() method in the UIBuilder.java(line no. 2178)
public void run() {
if(currentAction != null) {
if(Display.getInstance().isEdt()) {
postAsyncCommand(currentAction, currentActionEvent);
} else {
asyncCommandProcess(currentAction, currentActionEvent);
// wait for the destination form to appear before moving back into the LWUIT thread
waitForForm(destForm);
}
} else {
if(Display.getInstance().isEdt()) {
if(Display.getInstance().getCurrent() != null) {
exitForm(Display.getInstance().getCurrent());
}
Form f = (Form)createContainer(fetchResourceFile(), nextForm);
beforeShow(f);
f.show();
postShow(f);
} else {
if(processBackground(destForm)) {
waitForForm(destForm);
}
}
}
}
In the above method, since the currentAction is null, it always goes into the else statement and since the nextForm is also null, it causes the NullPointerException.
On further look at the UIBuilder.java code, I noticed what is causing the NullPointer exception. It seems when the FormListner is created, it is passed currentAction and currentActionEvent, however they are null at that time. Instead the code should be changed as follows(starting at line 2264):
if(action.startsWith("#")) {
action = action.substring(1);
Form currentForm = Display.getInstance().getCurrent();
if(currentForm != null) {
exitForm(currentForm);
}
Form f = (Form)createContainer(fetchResourceFile(), action);
beforeShow(f);
/* Replace following with next lines for fixing asynchronous command
if(Display.getInstance().getCurrent().getBackCommand() == cmd) {
f.showBack();
} else {
f.show();
}
postShow(f);
new Thread(new FormListener(currentAction, currentActionEvent, f)).start();
*/
new Thread(new FormListener(cmd, evt, f)).start();
return;
}
Can lwuit development team take a look at the above code, review and fix it. After I made the above change, the asynchronous command processing methods were invoked.
Thank you.
Thanks for the information, its probably better to use the issue tracker for things like this (at http://lwuit.java.net).
I will make a similar change although I don't understand why you commented out the form navigation portion.
To solve your use case of a wait screen we have a much simpler solution: Next Form. Just show the wait screen and in it define the "Next Form" property.
This will trigger a background thread to be invoked (processBackground callback) and only when the background thread completes the next form will be shown.
I'm having a very frustrating problem. I have a c# win application. When I have clicked the button, the program closes itself after executed the click event handler. Even if I have debugged the code unfortunately I can't see any error, It just quits the program.
Where am I going wrong?
Here is the Code:
private void btnOpenFolder_Click(object sender, EventArgs e)
{
DialogResult dg = fd1.ShowDialog();
if (dg == DialogResult.OK)
{
lblInput.Text = fd1.SelectedPath;
btnOpenFolder.Enabled = false;
timerCallback = new TimerCallback(tmrQualityEvent);
tmrQuality = new System.Threading.Timer(timerCallback, null, 0, 1000);
Thread qualityThread = new Thread(new ThreadStart(QualityMapOpenFolder));
qualityThread.Start();
QualityMapOpenFolder();
}
}
void QualityMapOpenFolder()
{
fileList.Clear();
string path = lblInput.Text;
if (Directory.Exists(path))
{
foreach (var file in Directory.GetFiles(path))
{
if (Path.GetExtension(file) != ".kml")
{
fileList.Add(file);
}
}
SetProgressBarValue(0);
ChangeFileNameLabel(fileList[0]);
FileName = fileList[0];
}
else
SetText("Please make sure you have correctly set the open folder path!", true);
dataListQuality = GetInputData();
SetText("Calculated Data has been created, please click process files...", false);
SetProcessButtonStatus(true);
}
Attach an event handler to the UnhandledException handler and log it. Should help you to find out why your application is crashing.
Update: Now that you have posted some code:
You seem to update UI elements from another thread which you start. You should access UI components only from the thread on which they were created (usually the main thread). Consider using a BackgroundWorker
You start the QualityMapOpenFolder method on a thread and then you also call it after you started the thread - this seems a bit weird and has probably some unexpected side effects.
The common reason for this kind of behavior is unhandled exception in background thread. To prevent program.
#ChrisWue wrote on how to detect this kind of exceptions.
Also, often Windows Application log provides an insight on unhandled errors.
See here how to prevent killing app in this case.