OC申请后台运行时间

//申请后台运行程序时间(当程序进去后台时，单位分钟)
- (void)applicationDidEnterBackground:(UIApplication *)application {
    [[UIApplication sharedApplication]beginBackgroundTaskWithExpirationHandler:nil];
    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(pushAction) userInfo:nil repeats:NO];
    NSLog(@"%@",timer);
}
 
- (void)pushAction{
    NSLog(@"申请后台运行时间，时间为0，点击home键，直接后台挂起程序");
}