I have some NSOperations that are started regularly in my application. They should complete even when the the application is put to background. For this, I'm using the beginBackgroundTaskWithExpirationHandler method.
Am I supposed to use the beginBackgroundTaskWithExpirationHandler/ endBackgroundTask: every time I start my task even if the app is not going to background? Or am I supposed the call the begin/end methods only when I detected a UIApplicationDidEnterBackgroundNotification?
Option 1: Use background task every time
/**
* This method is called regularly from a NSTimer
*/
- (void)processData
{
__block UIBackgroundTaskIdentifier operationBackgroundId = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
[[UIApplication sharedApplication] endBackgroundTask:operationBackgroundId];
operationBackgroundId = UIBackgroundTaskInvalid;
}];
NSOperation *operation = ...
[self.queue addOperation:operation];
operation.completionBlock = ^{
[[UIApplication sharedApplication] endBackgroundTask:operationBackgroundId];
operationBackgroundId = UIBackgroundTaskInvalid;
};
}
Option 2: Use background task only when the application is about to go to background
/**
* This method is called regularly from a NSTimer
*/
- (void)processData
{
NSOperation *operation = ...
[self.queue addOperation:operation];
}
- (void)applicationDidEnterBackground:(NSNotification *)notification
{
__block UIBackgroundTaskIdentifier operationBackgroundId = [[UIApplication sharedApplication] beginBackgroundTaskWithName:#"EnterBackgroundFlushTask" expirationHandler:^{
[[UIApplication sharedApplication] endBackgroundTask:operationBackgroundId];
operationBackgroundId = UIBackgroundTaskInvalid;
}];
// wait for all operations to complete and then
// let UIApplication know that we are done
[[UIApplication sharedApplication] endBackgroundTask:operationBackgroundId];
}
Answering my own question. From the Apple Docs:
You do not need to wait until your app moves to the background to
designate background tasks. A more useful design is to call the
beginBackgroundTaskWithName:expirationHandler: or
beginBackgroundTaskWithExpirationHandler: method before starting a
task and call the endBackgroundTask: method as soon as you finish. You
can even follow this pattern while your app is executing in the
foreground.
Other Apple API reference:
You should call this method at times where leaving a task unfinished might be detrimental to your app’s user experience.
You can call this method at any point in your app’s execution.
Option2 is correct option.Here is code from Apple document for your reference.
- (void)applicationDidEnterBackground:(UIApplication *)application
{
bgTask = [application beginBackgroundTaskWithName:#"MyTask" expirationHandler:^{
// Clean up any unfinished task business by marking where you
// stopped or ending the task outright.
[application endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
}];
// Start the long-running task and return immediately.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Do the work associated with the task, preferably in chunks.
[self processData];
[application endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
});
}
Apple developer Guide
Related
I had integrated pedometer and i am doing some calculation when the app is on background. But after 180sec my application get forcefully terminated by the Apple OS. Is there any way to run timer more than 180sec.
If time is of your concern and want to know exact after a specified interval , i suggest instead of using a timer you register for a local notification with fire date after your desired time interval.
If you need to perform a long task in background instead , you have to register it with system calling beginBackGroundTaskWithExpirationHandler method in this way :
- (void)applicationDidEnterBackground:(UIApplication *)application
{
bgTask = [application beginBackgroundTaskWithName:#"MyTask" expirationHandler:^{
// Clean up any unfinished task business by marking where you
// stopped or ending the task outright.
[application endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
}];
// Start the long-running task and return immediately.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Do the work associated with the task, preferably in chunks.
[application endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
});
}
you can also refer to link here : BackGroundTask
I have added data fetching operations to NSOperationQueue .During the process, I just put the device to sleep mode and the process gets stopped. I surfed stack overflow an get some basic ideas.I need help to continue my fetching process without any interruption when device moves to sleep mode.Help appreciated !!
NSManagedObjectContext *managedObjectContext=((AppDelegate *)[[UIApplication sharedApplication] delegate]).managedObjectContext;
NSOperationQueue *downLoadQueue=((AppDelegate *)[[UIApplication sharedApplication] delegate]).downloadqueue;
//Fetch operation
if([fetchqueue count]>0)
{
Queue *queue=[fetchqueue objectAtIndex:0];
queue.status=#"INP";
[managedObjectContext performBlockAndWait:^{
NSError * error = nil;
if (![managedObjectContext save:&error]){
NSLog(#"Unresolved error while loading3");
}
}];
DownloadOperation *downloadOp=[[DownloadOperation alloc]init];
downloadOp.queue=queue;
[downLoadQueue addOperation:downloadOp];
}
}
The downLoadQueue started its execution. It is fetching data from server meanwhile the device goes to sleep and the execution stops. I don't know how to continue in this block applicationDidEnterBackground. How can I get my lengthy downloading process during sleep mode?
Also tried this one..But the operation was not resumed.
//code follows
- (void)applicationDidEnterBackground:(UIApplication *)application
{
// Start the long-running task and return immediately.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSOperationQueue *downLoadQueue;
downLoadQueue=((AppDelegate *)[[UIApplication sharedApplication] delegate]).downloadqueue;
[downLoadQueue waitUntilAllOperationsAreFinished];
});
}
Please suggest any ideas.
I think the only way to do this is background task. Take a look at apple docs about this. There are also a lot of answers on stackowerflow how to implemet such feature.
I think in your case you can try next code to execute NSOperations a in backgraund task:
- (void)applicationDidEnterBackground:(UIApplication *)application
{
bgTask = [application beginBackgroundTaskWithName:#"MyTask" expirationHandler:^{
// Clean up any unfinished task business by marking where you
// stopped or ending the task outright.
[application endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
}];
// Start the long-running task and return immediately.
//Start your NSOperationQueue if it's not executing
//Lock current thread while operations are executing
[queue waitUntilAllOperationsAreFinished];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Do the work associated with the task, preferably in chunks.
[application endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
});
}
I am trying to update the location to server when the app is not running. I am getting the location update when user location is changed but the web service is not getting called... Any help is greatly appreciated.
You need implementation an background task like this
- (void)applicationDidEnterBackground:(UIApplication *)application
{
bgTask = [application beginBackgroundTaskWithName:#"MyTask" expirationHandler:^{
// Clean up any unfinished task business by marking where you
// stopped or ending the task outright.
[application endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
}];
// Start the long-running task and return immediately.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Do the work associated with the task, preferably in chunks.
[application endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
});
}
I'm developing an app in which I want to make a network call (syncing purpose) on an hourly basis. Even when the app is in the terminated state. How can I achieve this?
There is no UI Update involved anywhere, I just need to update local database and the cloud storage file.
developer apple BackgroundExecution
-(void)applicationDidEnterBackground:(UIApplication *)application
{
bgTask = [application beginBackgroundTaskWithName:#"MyTask" expirationHandler:^{
// Clean up any unfinished task business by marking where you
// stopped or ending the task outright.
[application endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
}];
// Start the long-running task and return immediately.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Do the work associated with the task, preferably in chunks.
[application endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
});
}
if([[UIDevice currentDevice] respondsToSelector:#selector(isMultitaskingSupported)])
{
__block UIBackgroundTaskIdentifier background_task;
background_task = [application beginBackgroundTaskWithExpirationHandler:^ {
[application endBackgroundTask: background_task];
background_task = UIBackgroundTaskInvalid;
}];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
while(YES)
{
[NSThread sleepForTimeInterval:your_sleep_time];
}
});
}
else
{
NSLog(#"Multitasking Not Supported");
}
We've created a new background task and add a new thread to it, so you can sleep the thread freely :)
I Hope I've help you
I want to upload some files which should continue even if the application goes into background.
Currently I am retrieving the files from the DB and than adding it to the Queue via NSOperation which is then starts the upload procedure.
All the files should be uploaded even if the app goes to background or foreground.
Below is the code for single task can anyone give me a hint how we can make it to work for uploading many files.
UIApplication* application = [UIApplication sharedApplication];
bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
// Clean up any unfinished task business by marking where you
// stopped or ending the task outright.
[application endBackgroundTask: bgTask];
bgTask = UIBackgroundTaskInvalid;
}];
Why not try doing this? .. I haven't yet tried it out, I'll post an update after attempting this
UIApplication* application = [UIApplication sharedApplication];
bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
// Clean up any unfinished task business by marking where you
// stopped or ending the task outright.
// Bring up your NSOperation queue instance here and block this thread until it is complete
[queue waitUntilAllOperationsAreFinished];
[application endBackgroundTask: bgTask];
bgTask = UIBackgroundTaskInvalid;
}];
also ensure that you have a way to cancel all these long standing operation in the background
bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
// Clean up any unfinished task business by marking where you.
// stopped or ending the task outright.
[queue cancelAllOperations];
[application endBackgroundTask:endSessionTask];
bgTask = UIBackgroundTaskInvalid;
}];
Apple allows background execution if your app follows and satisfy the necessary condition.
plese refer here