Multitasking in iOS 7
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This document discusses background capabilities in iOS 7. It summarizes the three new background modes available: background fetching, remote notifications, and background transfers. Background tasks now run for 3 minutes instead of 10 minutes. Apps can now download content in the background in response to push notifications or on a scheduled basis using background fetch APIs. Developers have close control while Apple prioritizes battery life and network usage.
![Change in background tasks handling (2/3)
// AppDelegate
UIBackgroundTaskIdentifier background_task;
!
- (void)applicationDidEnterBackground:(UIApplication *)application
{
if([[UIDevice currentDevice] respondsToSelector:@selector(isMultitaskingSupported)])
{
NSLog(@"Multitasking Supported");
if (background_task == UIBackgroundTaskInvalid) {
background_task = [application beginBackgroundTaskWithExpirationHandler:^ {
NSLog(@"Background task expirationn");
//Clean up code. Tell the system that we are done.
[application endBackgroundTask: background_task];
background_task = UIBackgroundTaskInvalid;
}];
//To make the code block asynchronous
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
//### background task starts
NSLog(@"Running in the backgroundn");
while(TRUE)
{
NSLog(@"Background time Remaining: %f",[[UIApplication sharedApplication] backgroundTimeRemaining]);
[NSThread sleepForTimeInterval:1]; //wait for 1 sec
}
//#### background task ends
//Clean up code. Tell the system that we are done.
[application endBackgroundTask: background_task];
background_task = UIBackgroundTaskInvalid;
});
}
else
{
NSLog(@"Multitasking Not Supported");
}
}
}
!
Universal Push Notification Platform](https://image.slidesharecdn.com/multitaskinginios7-131114101524-phpapp02/85/Multitasking-in-iOS-7-4-320.jpg)
![Change in background tasks handling (3/3)
On iOS 6, starts with 10 min:
2013-11-14 08:59:54.165 Background1[149:1103] Background time Remaining: 599.981943
!
!
On iOS 7, starts with 3 min:
2013-11-14 09:02:33.182 Background1[6315:1803] Background time Remaining: 179.942678
!
This is a big change for many apps using
background tasks.
!
I never seem task being scheduled discontinously …
Yet.
Universal Push Notification Platform](https://image.slidesharecdn.com/multitaskinginios7-131114101524-phpapp02/85/Multitasking-in-iOS-7-5-320.jpg)
Multitasking in iOS 7
- 1. Multitasking in iOS 7 Mickaël Rémond <mremond@boxcar.io> Universal Push Notification Platform
- 2. Pre-iOS 7 options for background modes Previously you had access to the following options: ! Audio playback Location update Task completion (up to 10 minutes) Newsstand download Voice-over-IP (VoIP) services Accessory or CoreBluetooth communication ! Specific limitations for each of them Universal Push Notification Platform
- 3. Change in background tasks handling (1/3) Apps will get scheduled when device is active and not keep it awake They still get up to 10 minutes run time, not guaranteed to be continuous ! WWDC 204 Universal Push Notification Platform
- 4. Change in background tasks handling (2/3) // AppDelegate UIBackgroundTaskIdentifier background_task; ! - (void)applicationDidEnterBackground:(UIApplication *)application { if([[UIDevice currentDevice] respondsToSelector:@selector(isMultitaskingSupported)]) { NSLog(@"Multitasking Supported"); if (background_task == UIBackgroundTaskInvalid) { background_task = [application beginBackgroundTaskWithExpirationHandler:^ { NSLog(@"Background task expirationn"); //Clean up code. Tell the system that we are done. [application endBackgroundTask: background_task]; background_task = UIBackgroundTaskInvalid; }]; //To make the code block asynchronous dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ //### background task starts NSLog(@"Running in the backgroundn"); while(TRUE) { NSLog(@"Background time Remaining: %f",[[UIApplication sharedApplication] backgroundTimeRemaining]); [NSThread sleepForTimeInterval:1]; //wait for 1 sec } //#### background task ends //Clean up code. Tell the system that we are done. [application endBackgroundTask: background_task]; background_task = UIBackgroundTaskInvalid; }); } else { NSLog(@"Multitasking Not Supported"); } } } ! Universal Push Notification Platform
- 5. Change in background tasks handling (3/3) On iOS 6, starts with 10 min: 2013-11-14 08:59:54.165 Background1[149:1103] Background time Remaining: 599.981943 ! ! On iOS 7, starts with 3 min: 2013-11-14 09:02:33.182 Background1[6315:1803] Background time Remaining: 179.942678 ! This is a big change for many apps using background tasks. ! I never seem task being scheduled discontinously … Yet. Universal Push Notification Platform
- 6. iOS 7 new background modes With iOS 7 you have three new modes: ! Background fetching Remote notification Background transfers ! All modes keep Apple and users in control to preserve battery life Universal Push Notification Platform
- 7. Project *info.plist: select background modes Two new modes available: ! fetch (App downloads content from the network) remote-notification (App download content in response to push notifications) Universal Push Notification Platform
- 8. Background fetch Universal Push Notification Platform
- 9. Background fetching: close control ! iOS stays in control: “Application launched opportunistically” Coalesced across applications means scheduled based on usage pattern sensitive to energy and data usage ! Users stay in control: Force close disable background fetch Dedicated setting panel Universal Push Notification Platform
- 10. Background fetching: user control Preferences -> General -> Background App Refresh Universal Push Notification Platform
- 11. Background fetching: usage patterns WWDC 204 Universal Push Notification Platform
- 12. Background fetching: App Delegate New delegate method on UIApplication is called - (void)application:(UIApplication *)application! performFetchWithCompletionHandler:(void (^) (UIBackgroundFetchResult! result))completionHandler;! ! Call the completion handler when fetch is complete to let iOS 7 learn about data availability patterns: UIBackgroundFetchResultNewData! UIBackgroundFetchResultNoData! UIBackgroundFetchResultFailed Universal Push Notification Platform
- 13. Background fetching: Limit server load At application launch: ! Define the minimum fetch interval to limit server load: - (void)setMinimumBackgroundFetchInterval: (NSTimeInterval)minInterval;! ! Use constants: const NSTimeInterval UIApplicationBackgroundFetchIntervalMinimum! const NSTimeInterval UIApplicationBackgroundFetchIntervalNever! ! More likely custom values (in seconds) Universal Push Notification Platform
- 14. Background fetching: Tips Simulate background fetch for testing Do not forget simulator has an option to manually trigger background fetch Limit operation to bare minimum You have at most 30 seconds of time to perform download operation Use NSURLSession to benefit from background download infrastructure Track background fetches per user on your server to discover patterns Universal Push Notification Platform
- 15. Remote notifications Universal Push Notification Platform
- 16. Remote notifs: Dev and Apple control Developers control: content-available set to 1 in APNS payload to tell the application content is available. ! Apple stays in control: Silent notification (without sound / alert / badge) can be delayed: Battery saving Normal notifications are send immediately Universal Push Notification Platform
- 17. Remote notifs: App Delegate New delegate method on UIApplication is called - (void)application:(UIApplication *)application! didReceiveRemoteNotification:(NSDictionary *)userInfo! fetchCompletionHandler:(void (^) (UIBackgroundFetchResult result))completionHandler;! ! Call the completion handler when download is complete to let iOS 7 learn about data availability patterns: UIBackgroundFetchResultNewData! UIBackgroundFetchResultNoData! UIBackgroundFetchResultFailed! Universal Push Notification Platform
- 18. Remote notifs: Tips ! Limit operation to bare minimum You have at most 30 seconds of time to perform download operation ! Use NSURLSession to benefit from background download infrastructure Universal Push Notification Platform
- 19. Background transfers Universal Push Notification Platform
- 20. Background transfers: Usage ! Used for data download and upload ! Used for granting iOS control over background operation ! Does not obsolete AFNetworking especially if you need parsing / serialization ! Quite a large piece of code with many options: Take the time to learn them, they are powerful Universal Push Notification Platform
- 21. Background transfers: Nice features ! Download / upload tasks in background ! Discretionary setting to save battery ! Limit download to Wifi only Universal Push Notification Platform
- 22. Background transfers: Tips ! Take the time to explore all the options / cases. To implement complex cases, data will flow through multiple paths in code ! Not “magic”: You still have to handle network failure and errors, resume on the next chunk Do not forget there is a server on the back that will timeout at some point ! Take it as a great toolbox to handle advanced cases Universal Push Notification Platform
- 23. References Talk example code https://github.com/boxcar/talk-code-examples/tree/ master/background-ios7 ! Background Modes in iOS Tutorial (pre-iOS 7) http://www.raywenderlich.com/29948/ backgrounding-for-ios ! WWDC 2013 Session 204: What’s new with multitasking. Universal Push Notification Platform