I would like to write a counter that shows how many seconds an app has be running for. (textView) and the counter should be cumulative and starts from where it left off. Im new to iphone sdk.
you are going to have to do these things:
get the time when the app starts in applicationDidFinishLaunching: in your application delegate
check if you have an old time using NSUserDefaults
have a thread that updates the ui (your textView display, may i suggest using a label instead) with the ever increasing time using NSThread or NSTimer - i recommend NSThread. you will also need to perform your updates on your ui thread as updating your ui from a background thread can just get lost in the post.
store the end time in applicationWillTerminate: in your application delegate using NSUserDefaults
lots of googling ahead of you, have fun!
Related
Restarting app development after a 15 year hiatus. Current project is conversion of old windows-type command line utility into interactive OS X windowed app.
I created a view delegate inside main window and can draw and update NSTable view.
The updates are generated in the App's main loop which takes a UDP/TCP stream, parses and updates view via appropriate delegation.
Here's the problem: When I run the app, the main window does not apparently get
focus (window control buttons on upper left are grey), the Menu created from my .xib is inert, and the window itself does not respond to resizing or to mouse hits inside the table view scroll bars. Also, the mouse pointer is the spinning beachball when over the App's window.
My guess is that I am not providing time to the Objective C run loop for event processing. I do send a "display" to my window on every iteration of my app loop, but I guess it is not sufficient (Apple is not very clear about what objects get what messages when sending this kind of update message). Am I on the right track?
Is there a way to let the system Event loop run an iteration each time through my app main loop?
Thanks!
Update: I tried explicitly providing event loop time in my app's main loop with:
[[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:0.1]];
There was no apparent change in app behavior.
My guess is that I am not providing time to the Objective C run loop for event processing.
In this case, I recommend you read about Grand Central Dispatch, which provides concurrency, allowing the GUI to remain responsive.
There's a good explanation of GCD here and whilst it looks like a large and complicated subject, you'll probably only need a few lines of code to make use of GCD. For example: -
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
// do some work
});
Despite comparing the nibs and connections between my code and a freshly created .xib prototype, i could find no reason for my code to not get focus.
The fix was to move my code guts into the project with a new .xib.
This works but is unsatisfying
I have a a few threads that needs to run constantly or be locked at my disposal. When I lock the phone or swap applications the thread seems to halt until the application is back in focus.
I have a class Worker that is a sub class of NSThread. There is a method called start which is called by the firstViewController that creates the Worker object.
//method start
[self performSelectorInBackground:#selector(run) withObject:self];
What do I need to do to make my thread run all the time, rather than only running while in focus?
Thanks :)
When your app enters the background, all threads as suspended - unless you've configured your application to use multi-tasking, and your work is being done using the multi-tasking methods. This is detailed at Apple developer.
In short, you basically can't have a thread running constantly in the background on iOS if you want to be accepted in the App store, unless you're a navigation or VOIP application. You can have a thread continue to run for around 10 minutes after you enter the background, but that's it.
I'm trying to figure out a way to have a timer that begins at the time that an app is installed and continues to run even when the app is in the background. I'm basically using the timer to periodically check the battery life of an external device that is linked to the phone. I've been told that the best way to do this is to use some sort of delegate calls to a timer function, but I'm fairly new to IOS and am pretty confused on how to do that. I know how to set up the timer and get the battery life, I'm however perplexed on how to keep the timer going through the life of the app. Any help you could give would be extreeemely appreciated! Thanks a bunch!
Running an app in the background (forever) isn't possible.
But while your app is running... you can set the repeats parameter of the method scheduledTimerWithInterval:target:selector:userInfo:repeats: to YES.
Here's a link to running it in the background for a certain period of time to perform a relatively large task.
run even when the app is in the background
Not possible. You can request an extra 10 minutes, but thats it. You will not be able to write your app as is.
For the timer part of your question, you can do this:
[NSTimer scheduledTimerWithTimeInterval:60.0
target:self
selector:#selector(checkBattery:)
userInfo:nil
repeats:YES];
But you should really be subscribing to the notifications on battery change events. Here is sample code from apple that shows how to do it.
coneybeare is right. This is iOS policy, which is in place exactly to prevent what you are trying to do, i.e. exhaust the iPhone's (or iPad's) battery life.
For the sake of learning i'm making a timer. Used an NSTimer but it appears this stops
when going to the background.
Thought of using NSDate instead. Does this work in the background?
Do i compare current time to a set time to get the timer running properly?
Some thoughts would be greatly appreciated!
If you are looking for something to handle time based events in the background, have a look at UILocalNotification. With a local notification, the OS will alert the user at the appointed time whether the app that scheduled the notification is running or not.
If you are looking for something to happen when the app starts, you can use NSUserDefaults and store a value containing the current timestamp. Fire this off when in the AppDelegate inside applicationWillResignActive method. You can then check this value in the applicationDidBecomeActive.
I'm working on an app for 4.0 using the background methods. I'm updating the user defaults with a number that is incremented each time the app is launched. Looks like in 4.0 didFinishLaunchingWithOptions doesn't fire each time the app is launched, only the first time it's launched if it's not already in the background. So right now, my user default is incrementing within the applicationDidBecomeActive method. Not sure if this is the right place. I did the same thing with Flurry Analytics and some other stuff that I want to instantiate each time the app is "launched".
I noticed that during an in-app purchase the applicationDidBecomeActive method fires twice. Not only is it falsely incrementing my user default as if the app was relaunched, it is also reinitializing flurry and the other items in the applicationDidBecomeActive method.
What am I doing wrong? Should I be using another method each time the app is "launched"?
Thanks,
Howie
Maybe you could try applicationWillEnterForeground instead of using applicationDidBecomeActive.