请问为什么要加这个通知？到前台又发进入后台的通知看上去不太合理

[frank-du]

- (void)applicationDidBecomeActive:(NSNotification *)notification {
    double systemVersion = [[UIDevice currentDevice].systemVersion doubleValue];
    if (systemVersion >= 12.0) {
        [[NSNotificationCenter defaultCenter]postNotificationName:UIApplicationDidEnterBackgroundNotification object:nil];
    }
}

谢谢!