UIImageView *backView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, SCREEN_WIDTH, TabBar_Height_1)];
    backView.image = [UIImage imageWithColor:[UIColor colorWithHex:0xffffff alpha:0.5]  size:CGSizeMake(SCREEN_WIDTH, TabBar_Height_1)];
    UIBlurEffect *effect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleLight];
    UIVisualEffectView *effectView = [[UIVisualEffectView alloc] initWithEffect:effect];
    effectView.frame = CGRectMake(0, 0, SCREEN_WIDTH, TabBar_Height_1);
    [backView addSubview:effectView];
 //這兩句話缺一不可  
    [rootTabBarController.tabBar insertSubview:backView atIndex:0];//新增到 tabbar 底層
    rootTabBarController.tabBar.backgroundImage = backView.image;//替換掉原生毛玻璃圖層