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Invoke or BeginInvoke cannot be called on a control until the window handle has been created
(8 answers)
Closed 9 years ago.
I have a WinForm screen that is also a message consumer (using Rhino ESB). If I try to update anything on the screen when I receive a message, nothing happens. A call to Invoke gives me an error that the handle is not created. The form is definitely created though, I'm firing a message on button click on the form and the background process sends a message back. It's with this return message I want to update the UI.
THIS IS NOT A DUPLICATE QUESTION, NONE OF THE SUGGESTED SOLUTIONS WORK.
I believe the difference here may be because I'm using Rhino Service bus. Rhino may be constructing a separate instance of my form rather than the one I'm using. I think what I probably need to do is to have Rhino use my instance of the form as the consumer by passing my instance into the IoC container Rhino is using. Another alternative is to move the Consumer off to it's own class and inject my Form into the consumer, and put a public method on my Form for the Consumer to use. This may work fine with my app because this is the main form and will never be disposed unless the app is closed. This would become problematic on another form that may be instantiated multiple times. Perhaps I could have my form "observe" another static object that a separate Consumer class updates. Please give suggestions as to the best approach.
public partial class MainForm : Form, ConsumerOf<MoveJobCompletedEvent>
{
public void Consume(MoveJobCompletedEvent message)
{
// This does nothing!
txtLogs.Text = "\nJob completed!";
}
}
This throws an error:
this.BeginInvoke((MethodInvoker)delegate
{
txtLogs.Text += "\nJob job completed!";
});
ERROR: Invoke or BeginInvoke cannot be called on a control until the window handle has been created.
It seems that you're consuming a JobCompleted event before the window handle is created. You could try the following:
public partial class MainForm : Form, ConsumerOf<MoveJobCompletedEvent>
{
public void Consume(MoveJobCompletedEvent message)
{
if (!this.HandleCreated)
return;
this.BeginInvoke((MethodInvoker)delegate
{
txtLogs.Text += "\nJob job completed!";
});
}
}
Related
I have more question while migrating the dialog from V3 to V4. below is our code.
In v3, we were using
Microsoft.Bot.Builder.Dialogs.Conversation.SendAsync(conversationContext.CurrentActivity, new RootDialog());
public class RootDialog : IDialog {
public RootDialog()
{
.....
}
public async Task StartAsync(IDialogContext context)
{
context.Wait(this.MessageReceivedAsync);
}
public virtual async Task MessageReceivedAsync(IDialogContext context, IAwaitable<IMessageActivity> result)
{
}
In the MessageReceivedAsync, we used the context.Wait(), context.Done() and context.PostAsync().
Can you recommend how to replace in the V4? And what's the alertnative for Microsoft.Bot.Builder.Dialogs.Conversation.SendAsync in V4?
These APIs are all gone. Here are the explanations of their replacements in V4:
context.Wait(…)
This method was used to tell the dialog system what method to invoke next on your class when a new activity arrived and is now gone. Instead you now subclass Dialog and override several methods for various lifecycle events:
BeginDialogAsync - called when the dialog is first pushed on the stack by bot code or another dialog calling BeginDialogAsync on the DialogContext.
ContinueDialogAsync - called when a new activity comes in and the bot calls ContinueDialog on the DialogContext.
ResumeDialogAsync - called when another dialog on the stack has completed and a dialog that was previously on the stack is now at the top of the stack.
RepromptDialogAsync - called when an explicit request has been made to reprompt the user. This is basically a way to tell the dialog that nothing has changed, but that it should pick up from where it left off again by sending whatever activity it last sent.
EndDialogAsync - called when the dialog has indicated its done and is being popped off the stack.
context.Done()/.Fail()
This was one of the way you reported the status of your dialog, but this is now accomplished by returning a DialogTurnResult from most of the aforementioned lifecycle methods. One of the properties is named Status and is of type DialogTurnStatus which has values that indicate the current state of the dialog. For example:
Waiting - the dialog sent some activities and is awaiting more input and should remain at the top of the stack.
Complete - the dialog has completed it's work and should be ended and popped off the stack. When this state is returned, callers can also investigate the output of the dialog (if it has one) which is passed back via the DialogTurnResult::Result property.
Cancelled - the dialog was cancelled part of the way through its work.
context.PostAsync()/Conversation.SendAsync
These were both used to respond back to the user. Both are now replaced by calling SendActivityAsync on the ITurnContext that is accessible via the Context property of the DialogContext instance that is passed into most of the aforementioned lifecycle methods as a parameter. NOTE: a couple of the lifecycle methods actually receive an ITurnContext parameter directly and then you just use that.
I want to make a custom camel processor to behave as a custom component.I read it as it as possible from http://camel.apache.org/processor.html - section--> Turning your processor into a full component.
Here the Custom Processor created will have to do the job when i call
someComponent://action1?param1=value1¶m2=value2
in the route.
For this i created a sample component using maven catalog.This created Endpoint,Consumer, Producer and Component classes.
The link says that the component should return ProcessorEndpoint which i have done.
So, Endpoint looks as below
public class SampleEndpoint extends ProcessorEndpoint{
// Automatically Generated code begins
public Producer createProducer() throws Exception{
return new SampleProducer(this, processor);
}
public Consumer createConsumer() throws Exception{
throw new UnsupportedOperationException("This operation is not permitted....");
}
// Automatically generated code ends here
//added below to make custom processor work for custom component
public Processor createProcessor(Processor processor){
return new SampleProcessor();
}
}
But, here the code in the processor is not getting executed instead the code in the SampleProducer gets executed.
Here i want the processor to be excuted.How do i do that?
When extending ProcessorEndpoint, the Producer from createProducer() will handle the exchange, i.e. Producer.process(Exchange exchange).
This is why you are seeing SampleProducer being used. But if you wanted to delegate to a processor, you could probably just change your code to be:
return new SampleProducer(this, new SampleProcessor());
My best advice would be to attach a debugger and put breakpoints in your SampleEndpoint, SampleProducer and SampleProcessor methods to see what gets called and when.
I'm not very experienced with this topic so forgive me if this isn't very clear.
I've created a Portable Class Library that has an ObservableCollection of Sections, and each secion has an ObservableCollection of Items.
Both of these collections are bound to the UI of separate Win8 and WP8 apps.
I'm trying to figure out the correct way to populate these collections correctly so that the UI gets updated from the PCL class.
If the class was inside the win8 project I know I could do something like Dispatcher.BeginInvoke, but this doesn't translate to the PCL, nor would I be able to reuse that in the WP8 project.
In this thread (Portable class library equivalent of Dispatcher.Invoke or Dispatcher.RunAsync) I discovered the SynchroniationContext class.
I passed in a reference to the main app's SynchroniationContext, and when I populate the sections I can do so because it's only the one object being updated:
if (SynchronizationContext.Current == _synchronizationContext)
{
// Execute the CollectionChanged event on the current thread
UpdateSections(sections);
}
else
{
// Post the CollectionChanged event on the creator thread
_synchronizationContext.Post(UpdateSections, sections);
}
However, when I try to do the same thing with articles, I have to have a reference to both the section AND the article, but the Post method only allows me to pass in a single object.
I attempted to use a lambda expression:
if (SynchronizationContext.Current == _synchronizationContext)
{
// Execute the CollectionChanged event on the current thread
section.Items.Add(item);
}
else
{
// Post the CollectionChanged event on the creator thread
_synchronizationContext.Post((e) =>
{
section.Items.Add(item);
}, null);
}
but I'm guessing this is not correct as I'm getting an error about being "marshalled for a different thread".
So where am I going wrong here? how can I update both collections correctly from the PCL so that both apps can also update their UI?
many thanks!
Hard to say without seeing the rest of the code but I doubt is has anything to do with Portable Class Libraries. It would be good to see the details about the exception (type, message and stack trace).
The way you call Post() with more than argument looks correct. What happens if you remove the if check and simply always go through SynchronizationContext.Post()?
BTW: I don't explicitly pass in the SynchronizationContext. I assume that the ViewModel is created on the UI Thread. This allows me to capture it like this:
public class MyViewModel
{
private SynchronizationContext _context = SynchronizationContext.Current;
}
I would recommend that at least in your ViewModels, all publicly observable state changes (ie property change notifications and modifications to ObservableCollections) happen on the UI thread. I’d recommend doing the same thing with your model state changes, but it might make sense to let them make changes on different threads and marshal those changes to the UI thread in your ViewModels.
To do this, of course, you need to be able to switch to the UI thread in portable code. If SynchronizationContext isn’t working for you, then just create your own abstraction for the dispatcher (ie IRunOnUIThread).
The reason you were getting the "marshalled on a different thread" error is that you weren't passing the item to add to the list as the "state" object on the Post(action, state) method.
Your code should look like this:
if (SynchronizationContext.Current == _synchronizationContext)
{
// Execute the CollectionChanged event on the current thread
section.Items.Add(item);
}
else
{
// Post the CollectionChanged event on the creator thread
_synchronizationContext.Post((e) =>
{
var item = (YourItemnType) e;
section.Items.Add(item);
}, item);
}
If you make that change, your code will work fine from a PCL.
How can you make a background web request and then update the UI, but have all the code that does the web requesting/parsing in a separate class so you can use it in multiple places? I thought I could use the classes methods as event handlers for a BackgroundWorker class, like
APIHelper mHelper = new APIHelper("http://example.com?foo=bar");
BackgroundWorker bw = new BackgroundWorker();
bw.DoWork +=new DoWorkEventHandler(mHelper.GetResponse);
bw.RunWorkerCompleted +=new RunWorkerCompletedEventHandler(mHelper.HandleResponse);
bw.RunWorkerAsync();
where APIHelper has the method
public void GetResponse(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = (BackgroundWorker) sender;
WebRequest request = HttpWebRequest.Create(this.URL);
IAsyncResult result = (IAsyncResult)
request.BeginGetResponse(ResponseCallback, request);
}
but then I don't know how to access the worker thread from ResponseCallback and, anyway, HandleResponse gets called first (obviously). (I tried putting in result.AsyncWaitHandle.WaitOne(); but I get a NotSupportedException error.) Yet I can't work out how to make the web request call synchronously. I'm clearly trying to go about this the wrong way, but I have no idea what the right way is.
ETA:
My aim is to be able to go:
user clicks (a) button(s) (on various pages)
a "working" message is displayed on the UI thread (and then input is blocked)
in a background thread my APIHelper class makes the relevant API call, gets the response, and passes it back to the UI thread; I only seem to be able to do this by starting another thread and waiting for that to return, because there's no synchronous web requests
the UI thread updates with the returned message (and input continues as before)
I can do the first two bits, and if I have the response, I can do the last bits, but I can't work out how to do the middle bit. Hopefully that made it clearer!
It took me several tried before I found there is a Dispatcher.
During the BackgroundWorker's dowork and complete methods you can call:
this.Dispatcher.BeginInvoke(() =>
{
// UPDATE UI BITS
});
I think the Dispatcher is only available in the view. So I'm not sure if the methods can exist outside of the xaml.cs
Put whatever you want to update in your UI; when updating an ObservableCollection you must do the update of you items in the Dispatcher.BeginInvoke too
This link might be a good read too:
http://www.windowsphonegeek.com/articles/All-about-Splash-Screens-in-WP7-ndash-Creating-animated-Splash-Screen
Update to assist notes
This is just a rough idea mind you...
bw.DoWork +=new DoWorkEventHandler(DoWork);
bw.RunWorkerCompleted +=new RunWorkerCompletedEventHandler(Complete)
// At least I think the EA is DoWork....
public void DoWork(object sender, DoWorkEventArgs e)
{
mHelper.GetResponse();
this.Dispatcher.BeginInvoke(() =>
{
UIObject.Visibility Collapse.
});
// Wait and do work with response.
});
}
public void Complete(object sender, RunWorkerCompleteEventArgs e)
{
this.Dispatcher.BeginInvoke(() =>
{
UIObject.Visible ....
});
}
I'd put all this logic in a viewmodel that the viewmodel of each page inherits from.
Have the pages bind to properties on the viewmodel (such as ShowLoading, etc.) which the model updates appropriately. i.e. before making the webrequest and in the callback.
As you won't be running the viewmodel code in the UI thread you also wouldn't need to run in a separate BackgroundWorker and you'll be able to access the properties of the viewmodel without issue.
It might be useful if you use a helper class that I have developed for WebDownload purposes during WP7 development.
I'm using it in 2-3 WP7 apps and no problem so far. Give it a go to see if it helps. You can get the class from the my blog linked bellow:
http://www.manorey.net/mohblog/?p=17#content
[NOTE] When working with this class you don't need to run anything in a background worker or new thread; it handles it all asynchronously.
I have an application that has a class named: UploadItem. The application creates uploading tasks based on information it has, for example, an upload needs to be created to upload a file to sitex.com with this the application creates a new UploadItem and adds that to an ObservableCollection, the collection is bound to a listview.
Now comes the part that I cannot solve.. I decided to change the structure so that people can create their own plugins that can upload a file, the problem lies with the fact that the UploadItem class has properties such as:
string _PercentagedDone;
public string PercentageDone
{
get { return _PercentagedDone; }
set { _PercentagedDone = value + "%"; NotifyPropertyChanged("PercentageDone"); }
}
But the plugin controls on how a file is uploaded, so how would the plugin edit the PercentageDone property that is located in the UploadItem class? If there is no way to do such a thing, then is there another way to achieve the same, i.e. showing the progress on the main GUI?
You'll want to define an interface for the plugins. Something like:
public interface IUploadPlugin
{
Task<bool> Upload(IEnumerable<Stream> files);
int Progress { get; }
}
The plugins then need to implement this interface and export themselves:
[Export(typeof(IUploadPlugin))]
public class MyUploader : IUploadPlugin, INotifyPropertyChanged
{
// ...
}
Notice that this plugin implements INotifyPropertyChanged. This is an easy way to handle updating the progress. Fire PropertyChanged on the Progress property and then databind your ProgressBar control in the main view to this property. Make sure that you fire PropertyChanged on the UI thread.
Another option would be to fire a custom event when the property changes. You could handle this event in the main view logic and update the progress.
Notice that I'm using Task for the return. This allows the caller to wait until the upload task finishes. You could use a callback instead, but with the CTP of the next version of .NET, using Task<> will allow you to use the await keyword for your async programming. Check it out here and here.