iOS程式進入後台後仍運行定時器NSTimer

步驟一：在Info.plist中，添加"Required background modes"鍵，value為：App plays audio

步驟二：

1. - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
   
2. {
   
3. self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
   
4. // Override point for customization after application launch.
   
5. NSError *setCategoryErr = nil;
   
6. NSError *activationErr = nil;
   
7. [[AVAudioSession sharedInstance]
   
8. setCategory: AVAudioSessionCategoryPlayback
   
9. error: &setCategoryErr];
   
10. [[AVAudioSession sharedInstance]
    
11. setActive: YES
    
12. error: &activationErr];
    
13. self.window.backgroundColor = [UIColor whiteColor];
    
14. [self.window makeKeyAndVisible];
    
15. return YES;
    
16. }

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步驟三：將以下代碼添加到appDelegate檔案中的- (void)applicationDidEnterBackgroundUIApplication
*)application函數，也可添加到在具體類中註冊的應用進入後台後的通知方法

1. - (void)applicationDidEnterBackground:(UIApplication *)application{
   
2. 
   
3. UIApplication* app = [UIApplication sharedApplication];
   
4. __block UIBackgroundTaskIdentifier bgTask;
   
5. bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
   
6. dispatch_async(dispatch_get_main_queue(), ^{
   
7. if (bgTask != UIBackgroundTaskInvalid)
   
8. {
   
9. bgTask = UIBackgroundTaskInvalid;
   
10. }
    
11. });
    
12. }];
    
13. dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    
14. dispatch_async(dispatch_get_main_queue(), ^{
    
15. if (bgTask != UIBackgroundTaskInvalid)
    
16. {
    
17. bgTask = UIBackgroundTaskInvalid;
    
18. }
    
19. });
    
20. });
    
21. }

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完成以上步驟你會發現，程式進入後台後仍可運行定時器！

原文連結：http://www.cnblogs.com/zzltjnh/archive/2013/05/15/3080058.html