I'm working on a small application using C++/wxWidgets, where several parts of the GUI need to be updated based on e.g. received UDP datagrams. More specifically, a secondary thread tries to keep a list of available "clients" in the network (which may come and go away) and e.g. corresponding comboboxes in the UI need to be updated to reflect the changes.
The documentation mentions that for this kind of thing EVT_UPDATE_UI would be a good choice. As far as I can understand from the sparse documentation, this event is sent automatically by the system and provides some support for assisted UI change.
However, I'd feel more comfortable using a more direct approach, i.e. where e.g. a window object could register/subscribe to receive notifications (either events or callbacks) upon particular events and another part of the code is sending out these notifications when required. I could do this in C++ using my own code, however I guess if wxWidgets already supports something like that, I should make use of it. However I haven't found anything in that regards.
So, the question is: does wxWidgets support this kind of notification system (or similar alternatives) or would I be best served coding my own?
AFAIK there is nothing directly usable in wxWidgets, but doing it on your own seems easy.
What I would do:
Create a wxEvtHandler-descendent class to hold the list of available "clients" in the network. Let this class have a wxCriticalSection, and use a wxCriticalSectionLocker for that in all methods that add or delete "clients".
Create a worker thread class by inheriting wxThread to handle your UDP datagrams, using blocking calls. The thread should directly call methods of the client list object whenever a client has to be added or removed. In these methods update the list of clients, and ::wxPostEvent() an event to itself (this will execute the whole notification calls in the main GUI thread).
Handle the event in the client list class, and notify all listeners that the list of clients has changed. The observer pattern seems to me a good fit. You could either call a method of all registered listeners directly, or send a wxCommandEvent to them.
Have you tried calling Update() on the widget(s) that change? Once you update the contents of the combo box, call Update(), and the contents should update.
Related
Can I extend the server-side Java Code in Worklight?
For example, there is a class called JavaScriptIntegrationLibraryImplementation under com.worklight.integration.js. Inside this class, there is a method broadcastNotification and I would like to override this method. Is it possible to do so?
EDIT
The reason is that:
When I make the subscription in client side with option field (e.g. add customType: A), I would like to retrieve a list of devices which have been subscribed to this event source. Base on the option field in deviceSubscrpition, I would like to have some business logic to determine who to send the notification message. For example, I will only submit the message to the user which 'customType=A'.
However, there is no API in Worklight which can retrieve a list of devices which make me to retrieve the list first. Then do the logic in JavaScript and called WL.Server.notifyDevice..
Therefore, I would like to check whether there is any method to retrieve a list of devices (through API / Adapter which connects to DB) which have subscribed to an event source.
Thanks.
This part of Worklight is not extendable. You can try and override this method as you say, but do note this is not supported and we cannot help in this case.
Edit
Now that it is clear what you're trying to achieve... what you are looking for currently not available. I will open a feature request for it and it will get evaluated at some point (if you are a customer of IBM, I suggest to get in touch with your contact...).
My suggestion (somewhat hackish in form): you could perhaps use multiple Event Sources, where each event source represents an iOS version. On the client-side, upon app initialization, you can retrieve the iOS version and use it to register to the correct event source (this would be very generic code to allow re-use). In case a new iOS version is released (you will likely know of this in advance), you simply add this event source to the adapter code and re-deploy the adapter. Users of the new iOS version could still register for notification, because you get the iOS version upon init, and use this information to register to the correct event source...
To reiterate:
The adapter contains: ES_iOS5 ES_iOS6
The client:
fetches iOS version, stores it in some variable.
registers to event source, where event source name is ES_${iOSVersion}
if a new iOS version is released, simply create a new event source and re-deploy
the adapter; the client is already equipped to handle this.
#Red23jordon,
i had similar case, i created a custom table where at the time of subscription, I was saving
user ID and event type in custom table. and when user unsubscribe then i also remove details from custom table.
For sending push to users subscribed to a particular "even type" i look into custom table to get list of user IDs subscribed to particular event type, and then i went into Notification user/device tables and fetching corresponding devices and sending Push.
Hope it may help you.
thanks
In my current project, there are lots of networking code, and it use the event handler to handle the input message. Is this mechanism different with the call back function ?
Typically not much. The handler is usually used in the context of a UI application where the UI control will call the handler to handle a UI event. The callback function is traditionally used from the C days (Function pointers) and also in the C++ (Functors) world.
As a general concept I would say that the call back functions are primarily used for Asynchronous execution. Where for example, client side function must look something up on the server and it may take a while. So instead of blocking it says :"Call back at this number (myCallBackFunction) when you are done looking up stuff on the server".
Now event handlers are just that: they handle some predefined events. Usually they wait for users to do something like click a button and then they spring into action. They typically but not necessarily expect some sort of input.
Hope this helps.
I've been fighting and fighting for some time with a decent way to handle a workflow based on a series of asynchronous ASIHTTPRequests (I am using queues). So far it seems to have eluded me and I always end with a hideous mess of delegate calls and spaghetti code exploding all over my project.
It works as follows:
Download a list of items (1 single ASIHTTPRequest, added to a queue).
The items retrieved in step 1 need to be stored.
Each item, from 1 is then parsed, queuing a 1 ASIHTTPRequest per item, for it's sub-items.
Each of the requests from step 3 are processed and the sub-items stored.
I need to be able to update the UI with the progress %age and messages.
I'm unable for the life of me to figure out a clean/maintainable way of doing this.
I've looked at the following links:
Manage Multiple Asynchronous Requests in iOS with ASINetworkQueue
Sync-Async Pair Pattern Easy Concurrency on iOS
But either I'm missing something, or they don't seem to adequately describe what I'm trying to achieve.
Could I use blocks?
I see myself facing a quite similar issue as I got the exercise to work on a app using a set of async http and ftp handlers in a set of process and workflows.
I'm not aware about ASIHTTP API but I assume I did something similar.
I defined a so called RequestOperationQueue which can for example represent all request operations of a certain workflow. Also I defined several template operations for example FTPDownloadOperation. And here comes the clue. I implemented all these RequestOperations more or less accroding to the idea of http://www.dribin.org/dave/blog/archives/2009/05/05/concurrent_operations/. Instead of implementing the delegate logic in the operation itself I implemented sth like callback handlers specialized for the different protocols (http, ftp, rsync, etc) providing a status property for the certain request which can be handled by the operation via KVO.
The UI can be notified about the workflow for example by a delegate protocol for RequestOperationQueue. for example didReceiveCallbackForRQOperation:(RequestOperation) rqo.
From my point of view the coding of workflows including client-server operations gets quite handy with this approach.
I've spend days trying to find a solution the problem i'm going to try to describe, i've googled alot and even looked at the .NET 4 reference source for SendReply and InternalSendReply activity. But until now i'm stuck.
To make the life of our end customers simpler i want to replace the Receive and SendReply activities with custom activites and use bookmarks instead.
I'm implementing a central webservice which can route to a correct workflow instance, that workflow modifies the bookmark value and finaly it creates a new bookmark while returning the modified bookmark value. It's rather complex already with a WorkflowServiceHostFactory which adds Behaviours and Attach a DataContractResolver to the endpoint.
The endpoint is derived from WorkflowHostingEndpoint which resolves a bookmark created in a custom activity (instead of a receive). And i want another activity instead of a sendreply. Those 2 should correlate and the custom sendreply does send a response on the open channel through the endpoint while creating a new bookmark.
The problem is that i didn't find a way yet to access the endpoint responseContext from within my custom send activity. On the other side, at the workflowcreating endpoint side, it seems that i'm not able to be notified whenever the workflow becomes Idle and as well i don't seem to be able to access the WorkflowExtensions from the host. i'm missing something?
A possible solution i've in mind might be not using a WorkflowServiceHost, but then i loose alot of AppFabric functionaly.
The workflowapplication in platform update 1 has some extension methods called RunEpisode with an overload Func called idleEventCallback. There it's possible to hook into the OnIdle and get a workflowextension to get the object to send back as response.
To answer my own question, i ended up in a workaround using the servicebroker functionality of sql server. The SqlDependency class where the workflow listens for the event to be fired whenever the workflow reach the activity that creates a new bookmark in another state.
I have a problem with the dnn module communication. I have a module that implements the module communication interface both listener and sender. in this module, I have a placeholder where I load a new ascx control. the problem is when I want to Communicate from this new dynamically loaded control. In this control i also implemented module communication interfaces( listener and sender). but when I call sender method, in this dynamic loaded control to update an other module (on same page)nothing happens. But then i call a " sender " from the dynamic loaded controls container control( the control where i have the placeholder) it works updating the other module on the same page. It seams that module comunications do not work in dynamic loaded ascx controls at all.
Is there anyone who have any idea , to solve this
/theonealf
I would guess that it's a timing issue. Try loading your dynamic control in the Init event, and see if it will catch the communication being sent.
Agree with #bdukes, Also there are additional things that I would recommend to check:
Check if there is any exception while nothing happens
Does your control inherits from PortalModuleBase? This will be required if you want to use moduleId, UserInfo, PortalId or any other dnn specific objects.
There can be other checks but it depends on your answer by trying above and #bdukes suggestion.
Honestly, I have had limited success with the communications interface. If you can get to work for your needs, then excellent. In case you find you need another solution, here's what I've done:
If I understand the question correctly, you're concerned with the specific use-case where one module needs to communicate with another module during the loading of a page. If that is so, you most likely have one module which is the one that needs to communicate, and one or more modules which need to pick up that communication.
I've used Context.Items in combination with the ASP.NET life cycle to solve this problem. The Items collection is just a bag that anything can be stuffed into or pulled out of. The module that needs to communicate can put things into that item bag during Page_Load:
var item = "My Thing";
Context.Items.Add("MyThingKey", item);
The modules which need to consume that thing can pull things out of that bag during PreRender.
var item = Context.Items["MyThingKey"].ToString();
The key is doing this during PreRender. This way, you are assured that the consuming of the communication happens after the production of the communication.
Good luck!