iOS 判断程序在前台还是后台运行

UIApplicationState state = [UIApplication sharedApplication].applicationState;

BOOL result = (state ==UIApplicationStateBackground);

NSLog(@"是后台运行: %@",result?@"YES":@"NO");

UIApplicationState state2 = [UIApplication sharedApplication].applicationState;  

BOOL result2 = (state2 ==UIApplicationStateActive);

NSLog(@"是前台运行: %@",result2?@"YES":@"NO");