改变tabbar的高度做法

UITabBarController *tabBarController =[[UITabBarController alloc] init];
CGRect frame = self.window.bounds;
tabBarController.tabBar.frame = CGRectMake(0, CGRectGetHeight(frame) - 98, CGRectGetWidth(frame), CGRectGetHeight(frame));
UIView *transitionView = [[tabBarController.view subviews] objectAtIndex:0];
frame.size.height = CGRectGetHeight(frame) - 98;
transitionView.frame = frame;