AppDelegate * app=(AppDelegate *)[[UIApplication sharedApplication]delegate];    UIWindow *window = app.window;    [UIView animateWithDuration:1.0f animations:^{        window.alpha = 0;        window.frame = CGRectMake(window.bounds.size.width/2.0, window.bounds.size.width, 0, 0);    } completion:^(BOOL finished) {        exit(0);    }];

有一个视觉效果，比较友好