加入如下程式碼，你的app就可以支援後臺運行了～很簡單
#import "AppDelegate.h"
static UIBackgroundTaskIdentifier bgTask;

@implementation AppDelegate

- (void)applicationDidEnterBackground:(UIApplication *)application {
    [self getBackgroundTask];
}

- (void)applicationWillEnterForeground:(UIApplication *)application {
    [self endBackgroundTask];
}

//獲取後臺任務
- (void)getBackgroundTask {
    
    NSLog(@"getBackgroundTask");
    UIBackgroundTaskIdentifier tempTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
        //後臺任務
    }];
    
    if (bgTask != UIBackgroundTaskInvalid) {
        [self endBackgroundTask];
    }
    
    bgTask = tempTask;
    
    [self performSelector:@selector(getBackgroundTask) withObject:nil afterDelay:120];
}

//結束後臺任務
- (void)endBackgroundTask {
    [[UIApplication sharedApplication] endBackgroundTask:bgTask];
    bgTask = UIBackgroundTaskInvalid;
}

@end