Responsive to keyboard frame in iOS

responsive_keyboard.swift

// in UIViewController

func setupHideKeypadWhenTappedAround() {
    let tap = UITapGestureRecognizer(target: self, action: #selector(handleTap))
    tap.cancelsTouchesInView = false
    view.addGestureRecognizer(tap)
    // responsive keyboard frame
    NotificationCenter.default.addObserver(self, selector: #selector(handleKeyboardWillChange),
    name: NSNotification.Name.UIKeyboardWillChangeFrame, object: nil)
}

@objc
private func handleTap(sender: UITapGestureRecognizer) {
    // hide keyboard
    view.endEditing(true)
}

@objc
private func handleKeyboardWillChange(sender: Notification) {
    // parsing notification
    let n = KeyboardNotification(sender)
    let keyboardFrame = n.frameEndForView(view: self.view)
    let duration = n.animationDuration
    let curve = n.animationCurve
    var frame: CGRect = self.view.frame
    frame.size = CGSize(width: frame.size.width, height: keyboardFrame.minY)
    willChangeViewFrame(frame, duration: duration, option: UIViewAnimationOptions(rawValue: UInt(curve << 16)))
}
/// Notify a view of UIViewController will be changes its frame
func willChangeViewFrame(_ to: CGRect, duration: Double, option: UIViewAnimationOptions) {
}




///
/// Helper struct to parse Notification of UIKeyboardWillChangeFrame

import UIKit

// https://gist.github.com/kristopherjohnson/13d5f18b0d56b0ea9242

/// Wrapper for the NSNotification userInfo values associated with a keyboard notification.
///
/// It provides properties that retrieve userInfo dictionary values with these keys:
///
/// - UIKeyboardFrameBeginUserInfoKey
/// - UIKeyboardFrameEndUserInfoKey
/// - UIKeyboardAnimationDurationUserInfoKey
/// - UIKeyboardAnimationCurveUserInfoKey
public struct KeyboardNotification {
    let notification: Notification
    let userInfo: Dictionary<String, Any>
    /// Initializer
    ///
    /// :param: notification Keyboard-related notification
    public init(_ notification: Notification) {
        self.notification = notification
        if let userInfo = notification.userInfo {
            self.userInfo = userInfo as! Dictionary
        } else {
            self.userInfo = Dictionary()
        }
    }
    /// Start frame of the keyboard in screen coordinates
    public var screenFrameBegin: CGRect {
        if let value = userInfo[UIKeyboardFrameBeginUserInfoKey] as? NSValue {
            return value.cgRectValue
        } else {
            return CGRect.zero
        }
    }
    /// End frame of the keyboard in screen coordinates
    public var screenFrameEnd: CGRect {
        if let value = userInfo[UIKeyboardFrameEndUserInfoKey] as? NSValue {
            return value.cgRectValue
        } else {
            return CGRect.zero
        }
    }
    /// keyboard animation duration
    public var animationDuration: Double {
        if let number = userInfo[UIKeyboardAnimationDurationUserInfoKey] as? NSNumber {
            return number.doubleValue
        } else {
            return 0.25
        }
    }
    /// Keyboard animation curve
    ///
    /// Note that the value returned by this method may not correspond to a
    /// UIViewAnimationCurve enum value.  For example, in iOS 7 and iOS 8,
    /// this returns the value 7.
    public var animationCurve: Int {
        if let number = userInfo[UIKeyboardAnimationCurveUserInfoKey] as? NSNumber {
            return number.intValue
        }
        return UIViewAnimationCurve.easeInOut.rawValue
    }
    /// Start frame of the keyboard in coordinates of specified view
    ///
    /// :param: view UIView to whose coordinate system the frame will be converted
    /// :returns: frame rectangle in view's coordinate system
    public func frameBeginForView(view: UIView) -> CGRect {
        return view.convert(screenFrameBegin, from: view.window)
    }

    /// End frame of the keyboard in coordinates of specified view
    ///
    /// :param: view UIView to whose coordinate system the frame will be converted
    /// :returns: frame rectangle in view's coordinate system
    public func frameEndForView(view: UIView) -> CGRect {
        return view.convert(screenFrameEnd, from: view.window)
    }
}