Hi all im trying to pause a function so some time in the middle of execution because ill have to wait for the call back functions from GData api and get my data ready to put in that function i dont know how to do that. I am developing in Xcode 4.2 really need some help
You need to consider redesigning a little bit. What ever portion of code you expect to process after callback happens, let that code called by the callback. That way it will give you the guarantee that it always executes after the callback.
where you want to wait your functionality write this code [self performSelector:#selector(WaitForTwoSecond) withObject:nil afterDelay:2]; and implement - (void)WaitForTwoSecond { //write your code here } this method wait for two second and after that you cant access all data and put it in appropriate place .
we can say that this function is working like in background process
Related
I wrote this little program which is supposed to print the current frontmost application twice, with a 3-second break in between.
void printFrontmostApp() {
NSRunningApplication *frontmostApplication = [NSWorkspace sharedWorkspace].frontmostApplication;
NSLog(#"%#",frontmostApplication);
}
int main(int argc, const char * argv[]) {
#autoreleasepool {
printFrontmostApp();
sleep(3);
printFrontmostApp();
}
return 0;
}
When I ran this program, I realised that frontmostApplication is not refreshed when it is called the second time. I found the solution here. But I still have two questions:
1) I want to know why the frontmostApplication is not updated.
2) How do I force it to refresh every time I call it? I don't want to receive a notification every time the frontmost application deactivates, because it is a little inefficient for my purposes.
Edit:
Just to be crystal clear, let's suppose the time now is 10:00:00. I call printFrontmostApp, and it prints "Xcode" to the console, because Xcode is the current frontmost app. Then the program sleeps for 3 seconds. At 10:00:01, I opened another app, say TextEdit. At 10:00:03, my program calls printFrontmostApp for the second time. I expect it to print "TextEdit", which is the current frontmost application. But it prints "Xcode" instead. I can't understand this behaviour.
Can someone please explain what happens at 10:00:03? The function seems to "remember" the value of frontmostApplication at 10:00:00 and retains it when it is called the second time. I thought that any memory will be released once it goes out of scope, so why is this happening?
And how do I get my program to get the frontmost app at 10:00:03? I can get the frontmost app at 10:00:00, I should be able to do the same 3 seconds later right?
The documentation for -[NSWorkspace runningApplications] — not the method you're using, but related — says:
Similar to the NSRunningApplication class’s properties, this property will only change when the main run loop is run in a common mode. Instead of polling, use key-value observing to be notified of changes to this array property.
From the NSRunningApplication documentation:
Properties that vary over time are inherently race-prone. For example, a hidden app may unhide itself at any time. To ameliorate this, properties persist until the next turn of the main run loop in a common mode. For example, if you repeatedly poll an unhidden app for its hidden property without allowing the run loop to run, it will continue to return NO, even if the app hides, until the next turn of the run loop.
It's a near certainty that the same principle applies to -frontmostApplication even though the documentation doesn't say so explicitly. You will never get different results by polling without allowing the run loop to run.
For 1) the answer is the same described in the question you have linked: You have to observe this notification, that tells you when a new application was activated:
NSWorkspaceDidActivateApplicationNotification
About 2) You have different observers for activation and deactivation like:
NSWorkspaceDidDeactivateApplicationNotification
So your are not going to observe notifications that you are not registered, please take a look at NSWorkspace Notifications for a comprehensive list.
Otherwise, please define your question about refreshing/polling (that I think it's not a good idea anyways).
I'm writing a small custom player based on libvlc. I've used much of the code from https://github.com/hartror/python-libvlc-bindings/blob/master/examples/gtkvlc.py that plays a single track just like I need.
Now I want to swtich to another track after previous has finished. To do that I catch callback "EventType.MediaPlayerEndReached" and in callback handler I write code:
<------>def endCallback(self,event):
<------><------>fname = vlc_controller.GetNextTrack()['url']
<------><------>self.w.set_title(fname)
<------><------>self.vlc.player.set_mrl(fname)
<------><------>self.w.set_title('after set_mrl')
<------><------>self.vlc.player.play()
<------><------>self.w.set_title('after play')
Now when this code gets executed it stucks on self.vlc.player.set_mrl(fname) and does not go any further and as a result I see NO NEXT TRACK.
I've tried different variations of this code using (vlc.stop(), vlc.set_media instead of vlc.set_mrl) but nothing works
Finally....
I think the best choise is to make multi threaded application on python
2 Threads:
Main thread - gtk.loop and displaying video an some other thinks
Additional thread that makes media switching.
For some time I was afraid of multithreading but now I know that this was the best way to do this task
For those facing similar issue in C# (Xamarin), per VLC documentation, calling the VLC object from an event tied to the object may freeze the application. So they said to use the code below inside the trigger event.
ThreadPool.QueueUserWorkItem(_ => PlayNext());
An example would be calling the code above inside the EndReach event.
Where PlayNext() is your own custom method to handle the next action you want to execute.
I struggled with this for about a day before seeing that portion of the documentation.
I am doing meta-programming with objective-C and try to automate some of an application functions. Thus, I am not changing the source code files and the view controllers of the application but from another file I am managing to get the UI navigation stack and I am using Objective-C Runtime Reference to find the tappable UI elements and the actions. for example for a button I found the target and action and call objc_msgSend to programatically fire the event.
step = (NSObject *)objc_msgSend(element.target, NSSelectorFromString(element.action));
However I need to be notified when the action was done, or in other word, I need to wait until the action was done and then continue my automation. I was thinking of using NSNotificationCenter
//To raise an event
[[NSNotificationCenter defaultCenter] postNotificationName:FIRE_EVENT_NOTIFICATION object:self];
but doesn't look like working.
I am even thinking of using Categories or
So I am not sure if there is anyway to wait for objc_msgSend and where should I continue.
It isn't entirely clear what you are trying to do and the exact problem that you are having but I'll have a go at answering your question.
If I understand correctly you are trying to fire the action associated with a UI element, presumably something like a button press. You have a reference to the element in element and you want to call the associated action on the elements target. The following assumes the action is an IBAction.
The simplest way to do this would presumably be:
[element.target performSelector:element.action];
Note: element.action almost certainly returns a SEL (a selector) not an NSString so there is no need to run it through NSSelectorFromString().
Normally, an IBAction event would receive the clicked on element as a parameter so I think you might want to do:
[element.target performSelector:element.action withObject:element];
IBAction's have no return value so there is nothing to store when the method returns.
performSelector: and performSelector:withObject: will only return once the called method has run to completion. You shouldn't need to organise some sort of notification of the action completing.
However, if the action you are calling is launching code on another thread then it is possible that the called action will return before the result of pressing the button has completed. This will be difficult to monitor without knowledge of the code that is being run.
If, for some reason, you have to use objc_msgSend then you would use the following:
objc_msgSend(element.target, element.action, element);
Like performSelector:, objc_msgSend will only return when the called method has run to completion.
Hopefully I have understood your question and my answer makes sense, it is entirely possible I'm barking up the wrong tree though.
I am looking to make an app that, after a given time of no use, will close or give a message to the user.
How can I implement this?
UKIDleTimer is what you're looking for. You create a timer that only fires when the system becomes idle and implement the following method in its delegate:
-(void) timerBeginsIdling: (id)sender {
// terminate app
[NSApp terminate];
}
How about:
[NSApp performSelector:#selector(terminate:)
withObject:nil
afterDelay:[your delay...]];
Look at various Hello World examples on the net for Objective C. Once you have a hello world example going, you'll want to add some event listeners to monitor user activity. When any of those event handlers are called as a result of a users' actions, they should set a variable with the time of that action. Finally, set up a timer to check for user inactivity, say once every 30 seconds, which checks that value, to see if it's exceeded the time at which you want the application to close. If so, then send an exit command.
Hi I would like to pause the execution of a function in an cocoa project. I dont want to use sleep() because the function needs to resume after user interaction. I also want to avoid doing this with multiple calls to sleep.
Thanks for your responses. Ok I started the code while waiting for some answers. I then realized that sleep or pause would not be usefull to me because it freeses my whole program. I think I might have to do some threading. Here is the situation:
I have a program that uses coreplot. I also use it to debug and develop algorithms so I do lots of plots while the data is being processed (ie in the midfle of the code but I need the flexibility to put it anywhaere so I cant separate my function). I was able to do this with NSRunAlertPanel but having a message box like that doesnt make it very presentable and I cant do much with the main window while an alert is open.
I hope I am not too confusing with my explanation but if I am ill try to one line it here:
I would like to interact with my cocoa interface while one of my functions is stopped in the middle of what it is doing.
Its sounds to me like you're looking for -NSRunLoop runUntilDate:
Apple's Docs: runUntilDate
This code will cause the execution within your method to pause but still let other events like timers and user input occur:
while ( functionShouldPause )
{
[[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:1]];
}
Switching functionShouldPause back to false will allow the rest of the method to execute.
It seems more like you are interested in reacting to user events rather than "pausing" the function. You would probably want to put the code that you want to execute into another function that is called as a result of the user's actions.
In C you can use the pause() function in <unistd.h>. This causes the calling program to suspend until it receives a signal, at which point the pause call will return and your program will continue (or call a signal handler; depending on what signal was received).
So it sounds like you want to break the function into two parts; the bit that happens before the sleep and the bit that happens afterward. Before going to sleep, register for a notification that calls the "after" code, and can be triggered by the UI (by an IBAction connected to whatever UI element). Now instead of calling sleep(), run the run loop for the period you want to go to sleep for, then after that has returned post the "after" notification. In the "after" code, remove the object as an observer for that notification. Now, whichever happens first - the time runs out or the user interrupts you - you get to run the "after" code.
Isn't there a clock or timer function? When your button is pressed start running a loop like timeTillAction = 10 and do a loop of timeTillAction = timeTillAction - 1 until it reaches 0 then run whatever code after the 10 seconds.
Sorry if this isn't well explained.