iOS 项目一直在后台执行

我后来是这么解决不知道行不行，能够长期的在后台执行

首先我在xx-info.plist 里的 "Required background modes" 里增加"App provides Voice over IP services"

然后在delegate里增加下面代码，原理是进入后台时程序会在600秒那样结束任务，我做的就是在结束任务前新开一个任务。再结束旧任务，这样就一直的在后台执行，希望可能帮助到很多其它的人。我也查了非常久才找到这种方法的。

UIBackgroundTaskIdentifier
 backgroundTaskIdentifier;

`02`	`UIBackgroundTaskIdentifier oldBackgroundTaskIdentifier;`

03

`04`	`- (BOOL) isMultitaskingSupported{`

05

`06`	`BOOL result = NO;`

07

`08`	`if` `([[UIDevice currentDevice]`

09

`10`	`respondsToSelector:@selector(isMultitaskingSupported)]){ result = [[UIDevice currentDevice] isMultitaskingSupported];`

11

12 }

13

`14`	`return` `result;`

15

16 }

17

`18`	`- (void) timerMethod:(NSTimer *)paramSender{`

`19`	`count++;`

`20`	`if` `(count % 500 == 0) {`

`21`	`UIApplication *application = [UIApplication sharedApplication];`

22

`23`	`//开启一个新的后台`

24

`25`	`backgroundTaskIdentifier = [application beginBackgroundTaskWithExpirationHandler:^{`

26

27 }];

`28`	`//结束旧的后台任务`

`29`	`[application endBackgroundTask:backgroundTaskIdentifier];`

`30`	`oldBackgroundTaskIdentifier = backgroundTaskIdentifier;`

31 }

`32`	`NSLog(@"%ld",count);`

33 }

`34`	`- (void)applicationDidEnterBackground:(UIApplication *)application`

35 {

`36`	`if` `([self isMultitaskingSupported] == NO){`

37

`38`	`return; }`

`39`	`//开启一个后台任务`

40

`41`	`backgroundTaskIdentifier = [application beginBackgroundTaskWithExpirationHandler:^{`

42 }];

`43`	`oldBackgroundTaskIdentifier = backgroundTaskIdentifier;`

`44`	`if` `([self.myTimer isValid]) {`

`45`	`[self.myTimer invalidate];`

46 }

`47`	`self.myTimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timerMethod:) userInfo:nil repeats:YES];`

48 }

49

`50`	`- (void)applicationWillEnterForeground:(UIApplication *)application`

51 {

`52`	`if` `(backgroundTaskIdentifier != UIBackgroundTaskInvalid){`

`53`	`[application endBackgroundTask:backgroundTaskIdentifier];`

`54`	`if` `([self.myTimer isValid]) {`

`55`	`[self.myTimer invalidate];`

56 }

57 }

58 }

59

`60`	`- (void)applicationWillEnterForeground:(UIApplication *)application`

61 {

`62`	`if` `(backgroundTaskIdentifier != UIBackgroundTaskInvalid){`

`63`	`[application endBackgroundTask:backgroundTaskIdentifier];`

`64`	`if` `([self.myTimer isValid]) {`

`65`	`[self.myTimer invalidate];`

66 }

67 }

68 }

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