Can we call the method after the application has been minimized? - iphone

Question

iOS
Can we call the method after the application has been minimized?
For example, 5 seconds after was called applicationDidEnterBackground:.
I use this code, but test method don't call
- (void)test
{
printf("Test called!");
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
[self performSelector:#selector(test) withObject:nil afterDelay:5.0];
}

Answer 1

You can use the background task APIs to call a method after you've been backgrounded (as long as your task doesn't take too long - usually ~10 mins is the max allowed time).
iOS doesn't let timers fire when the app is backgrounded, so I've found that dispatching a background thread before the app is backgrounded, then putting that thread to sleep, has the same effect as a timer.
Put the following code in your app delegate's - (void)applicationWillResignActive:(UIApplication *)application method:
// Dispatch to a background queue
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
// Tell the system that you want to start a background task
UIBackgroundTaskIdentifier taskID = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
// Cleanup before system kills the app
}];
// Sleep the block for 5 seconds
[NSThread sleepForTimeInterval:5.0];
// Call the method if the app is backgrounded (and not just inactive)
if (application.applicationState == UIApplicationStateBackground)
[self performSelector:#selector(test)]; // Or, you could just call [self test]; here
// Tell the system that the task has ended.
if (taskID != UIBackgroundTaskInvalid) {
[[UIApplication sharedApplication] endBackgroundTask:taskID];
}
});