I am developping an objective c application and I would like to detect non responsives windows even if they are not own by my application.
Is there a way to be notified when a such case occurs?
Thanks in advance for your help,
Regards,
I think the only way to detect whether an window is hanging is to detect when its application is hanging. And I think the only way to - reliably - do this is to talk to it. Send it some inter-process message and await an action. I think that's exactly how the system detects it: there is some delay before the beach ball appears. And this is because the system sent a message and received no answer in x seconds.
What kind of message that might be is hard to say. Must be something that goes through the main event loop but can be sent by every application. I'm sure Google will be of some help finding it. I'm no pro in inter-process communications and would have to search as well.
You can use the Instruments application with a "Spin Monitor" instrument track. If you set it to monitor "All Processes", it will capture stack traces whenever an application hangs (doesn't process the main event loop for a long time).
Related
I have an application where I need to create local notifications via polling without doing push - primarily due to client infrastructure limitations and their security model.
I've read: http://www.objc.io/issue-5/multitasking.html, I've seen David Chan's WWDC presentation - where single push messages kick off download tasks - but what I truly need is background fetch - on a regular basis - like every ten minutes - in iOS 7.
I've seen the VOIP hacks. No. What non-hack way is there to do this without user interaction or push messages? Any examples you can point me to?
Here's what I know:
Background data tasks will work in the debugger but if you can get a console on an IPA, you'll quickly find out they really are prohibited (thereby invalidated many examples).
Background URL tasks require custom delegates - but fetch completion handlers are iffy. This too I found with an IPA and console.
I would love to avoid using the AFNetworking lib - for something quite simple.
Background fetch is not a reliable solution - you are at the mercy of the OS, and it is not very merciful. Abusing iOS background modes is not a reliable solution - Apple is known to reject applications that enable background modes, such as location, VOIP and music playback, without a legitimate reason. Background URL tasks are not something you can rely upon to wake your app; they will wake it, but the app will not be awake enough in the background to enqueue a background URL task.
Your best and most intended method is still background fetch, but be prepared to be disappointed. Your app will not be woken app in the interval you need. Also, the user can kill the app in the app switcher screen, causing your app to never wake up until opened.
No real reliable method other than push. You need to insist with your client for the sake of user experience.
Unfortunately there is no "reliable" way to do that on iOS. With the background fetch API you are not guaranteed to have process run when you would like it run. As you've said, you've already looked at the API so i'm probably telling you something that you already know. A local notification wouldn't solve your issue either as this isn't a way that you can wake your application up and kick off network events. This is behavior that Apple doesn't want as this would negate the whole purpose of their background task coalescing.
You really need to have a push mechanism in place for something like this, so if this is something that is needed, then you may have to stress that to the client.
Using the iPhone and objective C, is there a way to stall or perform a timing loop to allow for the GPS to catch up and return a valid set of coordinates?
Currently, the application runs too quickly and the GPS cannot supply the coordinates fast enough...
Since you said you're on iPhone, you're using CLLocationManager. Just set a delegate on the manager and wait for the locationManager:didUpdateToLocation:fromLocation: message to know when the GPS data is ready.
Assuming your GPS polling is running in a different thread to the User Interface, you can call the static NSThread functions sleepForTimeInterval or sleepUntilDate from the thread that is waiting for the GPS data.
If your mobile application is using GPS, your application should be prepared for location updates, even if your application doesn't track movements..
A common case would be where the user put your application in background and activate it later on a completely different location.
On iOS, create an implementation of CLLocationManagerDelegate like Anomie wrote. And use the timestamp of the update to evaluate the freshness of the location.
Don't sleep & poll like other people suggested.
Either block to wait for data or don't update anything if no data received. There is of course usleep(), but without showing code and specifically how your loop is executed and by what mechanism (threaded or not) we can only answer in general terms.
I have a windows mobile application
I have noticed that it properly terminate on exiting, they simply minimize and take up memory. I need to cehck whether any instance of the same application is running in the taskmanager.If exists, i need to kill the process.
I need to write small app that would loop through all open application processes and terminate the required one.
Does such an application exist? If not, which onecould I use to write my own app for it?
Typically this is not how you solve this problem.
You should hold a 'mutex' in your application, and when it launches a second time, you first check this mutex, and if it's taken, you know your app is already running.
Find an appropriate global mutex to hold, and then check for it (I'm not sure what sort you can use on whatever version of Windows Mobile you are targetting, but a trivial search should help you find the answer).
If your app shows an [X] in the corner that's a Minimize button. Change the MinimizeButton property of the form and it will become an [ok] button which will close it.
The CF under Windows Mobile already enforces application singleton behavior. If the app is already running, the CF will look for it, find it, and bring it to the fore for you. No extra work needed.
If you really want to find the process and terminate it, that's done with the toolhelp API set. You can P/Invoke it or use the classes in the Smart Device Framework.
I have a rather unusual problem. I am using xpdfprint binary for the print job from my application. But if the user has a "directly print to the printer" setting enabled and by mistake if the printer is not available (power failure or cord not plugged in) then the application hangs. It seems to be a standard behaviour since in my machine other windows applications also behave the same way. Problem is, in this case the printer timeout is not happening, neither it returns an error. It is waiting on the synchronous call to finish the printing. Is there anyway I can handle this situation? I am forced to find a solution because of a demanding customer. If by some means I get the physical printer status before the printing job is sent, I could solve this problem to an extent. Mine is a windows application and the coding is largely done in C#. If anybody has a win32 sample code please share with me.
Thanks in advance for any kind of help.
If the printer isn't connected then don't have a print menu item enabled, with a message.
Then, you just check every so often on the status.
You may find this of interest to check the status:
http://www.codeproject.com/KB/printing/printeroffline.aspx
I have an application that needs to "poll" a webservice to see if the user has any new messages waiting. I have no control over the webservice so I cannot switch to a "push" mechanism, I'm stuck making a request every X number of seconds to see what's available.
I am using a System.Threading.Timer to make the request every so often, but am encountering a few problems. The biggest is that it stops running when the phone is sent into "standby" mode (screen off, but still able to get calls and email/txt notifications).
I'd really like it to behave like other background applications. What can I do to make it work without being too big of a drain on the battery?
Hate to answer my own question, but I was pointed to this, which was able to perform even when the device is asleep. Looks like it's working perfectly.
There's nothing you can do, AFAIK. Standby mode is meant to suspend the processor to save power, and there's no way your code can execute if the processor isn't running. There are things your application can do to prevent the device from going into standby mode, but this really isn't advisable at all.
Yep. Similar to how MusiGenesis has answered, you won't be able to do much without keeping the device up and running. Similar to how some phones will notify that "Game/App Running" and thus your battery is being slapped around.
What about writing an interface from your phone to leverage text messaging (which still works) and get it to send a text message to the web service? Would that be possible? I'm guessing that sort of method might also stop running, but I figure it's a thought?
I'm not sure about compact framework, but in Win32 there is WaitableTimer that can wake up computer from standby. It takes some native calls though as there's no wrapper in .Net.
Although you can't modify the webservice, you might be able to add a second "shadow" webservice in between your clients and the original webservice. The shadow webservice could poll the original webservice and then "push" anything it finds out to the PDAs.
I think you might still have the same problem, though. I've never done "push" from a webservice, but I think it's basically implemented by having the client make an initial call to a webservice method that takes a delegate to a method in the client, which the webservice then hangs onto. When the webservice needs to push something, it calls that delegate. If the client has gone into standby mode in the meantime, the attempt to call the delegate from the server will fail.