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Đẩy TextField lên trên bàn phím

Chúng ta có một vấn đề như thế này: nếu Text Field ở gần phía đấy màn hình, khi keyboard được bật lên nó sẽ che mốt ô text cần nhập. Chúng ta sẽ cần xử lý để đẩy ô Text Field lên phía trên của Key board



Chúng ta sẽ phải lắng nghe sự kiện ẩn, hiện của keyboard

 NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(notification:)), name: .UIKeyboardWillShow, object: nil) 
NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide(notification:)), name: .UIKeyboardWillHide, object: nil)

 @objc func keyboardWillShow(notification: NSNotification) {
        if let keyboardSize = (notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
            guard let globalPoint =  textField.superview?.convert(textField.frame.origin, to: nil) else {
                return
            }
            if globalPoint.y + 50 > heightScreen - keyboardSize.height {
                distanceConstraint.constant = CGFloat(keyboardSize.height - (heightScreen - globalPoint.y) + 50)
            }
        }
    }

    @objc func keyboardWillHide(notification: NSNotification) {
        if distanceConstraint.constant > 0 {
            distanceConstraint.constant = CGFloat(0)
        }
    }

textField : Text Field cuối cùng

textField.superview?.convert : là câu lệnh để quy đổi tới hệ toạ độ trên màn hình
50 : là chiều cao của Text Field 40dp công thêm một khoảng 10dp

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