Tab 设置圆角
self.tabBar.backgroundImage = [[UIImage alloc]init];
self.tabBar.shadowImage = [[UIImage alloc]init];
self.tabBar.translucent = NO;
self.tabBar.layer.masksToBounds = YES;
self.tabBar.layer.cornerRadius = 15.0;
if ( @available(iOS 11.0, *)) {
self.tabBar.layer.maskedCorners = kCALayerMinXMinYCorner | kCALayerMaxXMinYCorner;
}
