MBProgressHUD在确定模式下不是动画

Question

MBProgressHUD在将mode设置为.determinate时不会设置动画，只是显示圆圈而不是动画。

self.progressHUD = MBProgressHUD.showAdded(to: self.view, animated: true)
self.progressHUD?.mode = .determinate
self.progressHUD?.contentColor = .purple