注冊通知

NotificationCenter.default.addObserver(self, selector: #selector(ComposeViewController.keyboardWillChangeFrame(node:)), name: Notification.Name.UIKeyboardWillChangeFrame, object: nil)

移除通知

deinit {
    NotificationCenter.default.removeObserver(self)
}

監(jiān)聽鍵盤高度變化

@objc private func keyboardWillChangeFrame(node : Notification){
    //1.獲取動畫執(zhí)行的時間
    let duration =  node.userInfo!["UIKeyboardAnimationDurationUserInfoKey"] as! Double
    //2. 獲取鍵盤最終的Y值
    let endFrame = (node.userInfo!["UIKeyboardFrameEndUserInfoKey"] as! NSValue).cgRectValue
    let y = endFrame.origin.y
    //3.計算工具欄距離底部的間距
    let margin =  UIScreen.main.bounds.height - y
    //4.執(zhí)行動畫
    toolBarBottomCons.constant = margin
    UIView.animate(withDuration: duration) {
        self.view.layoutIfNeeded()
    }
}

常用的通知的名字
. 監(jiān)聽軟鍵盤的彈出
.UIKeyboardWillShow
. 監(jiān)聽軟鍵盤的收起
.UIKeyboardWillHide
.監(jiān)聽軟鍵盤的高度變化
.UIKeyboardWillChangeFrame