swift 监听键盘弹出的高度

      // 监听键盘通知
        NotificationCenter.default.addObserver(self, selector: #selector(ComposeViewController.keyboardWillChangeFrame(note:)), name: NSNotification.Name.UIKeyboardWillChangeFrame, object: nil)

    //监听键盘的事件
    func keyboardWillChangeFrame(note: Notification) {

        print(note.userInfo ?? "")
        // 1.获取动画执行的时间
        let duration = note.userInfo?[UIKeyboardAnimationDurationUserInfoKey] as! TimeInterval

        // 2.获取键盘最终 Y值
        let endFrame = (note.userInfo?[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
        let y = endFrame.origin.y

        //计算工具栏距离底部的间距
        let margin = UIScreen.main.bounds.height - y
        print(margin)
        // 更新约束,执行动画
        toolBarBottom.snp.updateConstraints { (make) in
            make.left.equalTo()
            make.right.equalTo()
            make.height.equalTo()
            make.bottom.equalTo(-margin)
        }
        UIView.animate(withDuration: duration) {
            self.view.layoutIfNeeded()
        }
    }