A floating button on iOS for http://stackoverflow.com/q/34777558/77567

FloatingViewController.swift

import UIKit

class FloatingButtonController: UIViewController {

    private(set) var button: UIButton!

    required init?(coder aDecoder: NSCoder) {
        fatalError()
    }

    init() {
        super.init(nibName: nil, bundle: nil)
        window.windowLevel = CGFloat.max
        window.hidden = false
        window.rootViewController = self

        NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardDidShow:", name: UIKeyboardDidShowNotification, object: nil)
    }

    private let window = FloatingButtonWindow()

    override func loadView() {
        let view = UIView()
        let button = UIButton(type: .Custom)
        button.setTitle("Floating", forState: .Normal)
        button.setTitleColor(UIColor.greenColor(), forState: .Normal)
        button.backgroundColor = UIColor.whiteColor()
        button.layer.shadowColor = UIColor.blackColor().CGColor
        button.layer.shadowRadius = 3
        button.layer.shadowOpacity = 0.8
        button.layer.shadowOffset = CGSize.zero
        button.sizeToFit()
        button.frame = CGRect(origin: CGPointMake(10, 10), size: button.bounds.size)
        button.autoresizingMask = []
        view.addSubview(button)
        self.view = view
        self.button = button
        window.button = button

        let panner = UIPanGestureRecognizer(target: self, action: "panDidFire:")
        button.addGestureRecognizer(panner)
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        snapButtonToSocket()
    }

    func panDidFire(panner: UIPanGestureRecognizer) {
        let offset = panner.translationInView(view)
        panner.setTranslation(CGPoint.zero, inView: view)
        var center = button.center
        center.x += offset.x
        center.y += offset.y
        button.center = center

        if panner.state == .Ended || panner.state == .Cancelled {
            UIView.animateWithDuration(0.3) {
                self.snapButtonToSocket()
            }
        }
    }

    func keyboardDidShow(note: NSNotification) {
        window.windowLevel = 0
        window.windowLevel = CGFloat.max
    }

    private func snapButtonToSocket() {
        var bestSocket = CGPoint.zero
        var distanceToBestSocket = CGFloat.infinity
        let center = button.center
        for socket in sockets {
            let distance = hypot(center.x - socket.x, center.y - socket.y)
            if distance < distanceToBestSocket {
                distanceToBestSocket = distance
                bestSocket = socket
            }
        }
        button.center = bestSocket
    }

    private var sockets: [CGPoint] {
        let buttonSize = button.bounds.size
        let rect = view.bounds.insetBy(dx: 4 + buttonSize.width / 2, dy: 4 + buttonSize.height / 2)
        let sockets: [CGPoint] = [
            CGPointMake(rect.minX, rect.minY),
            CGPointMake(rect.minX, rect.maxY),
            CGPointMake(rect.maxX, rect.minY),
            CGPointMake(rect.maxX, rect.maxY),
            CGPointMake(rect.midX, rect.midY)
        ]
        return sockets
    }

}

private class FloatingButtonWindow: UIWindow {

    var button: UIButton?

    init() {
        super.init(frame: UIScreen.mainScreen().bounds)
        backgroundColor = nil
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }


    private override func pointInside(point: CGPoint, withEvent event: UIEvent?) -> Bool {
        guard let button = button else { return false }
        let buttonPoint = convertPoint(point, toView: button)
        return button.pointInside(buttonPoint, withEvent: event)
    }
    
}

can you please update code for iOS 13 and above when scene delegate is used

can you please update code for iOS 13 and above when scene delegate is used

import UIKit

class FloatingButtonController: UIViewController {

    private(set) var button: UIButton!

    required init?(coder aDecoder: NSCoder) {
        fatalError()
    }

    init(scene: UIWindowScene) {
        window = FloatingButtonWindow(scene: scene)
        super.init(nibName: nil, bundle: nil)
        window.windowLevel = UIWindow.Level(rawValue: CGFloat.greatestFiniteMagnitude)
        window.isHidden = false
        window.rootViewController = self

        NotificationCenter.default.addObserver(self, selector: #selector(keyboardDidShow(note:)), name: UIResponder.keyboardDidShowNotification, object: nil)
    }

    private let window: FloatingButtonWindow

    override func loadView() {
        let view = UIView()
        let button = UIButton(type: .custom)
        button.setTitle("Floating", for: .normal)
        button.setTitleColor(UIColor.green, for: .normal)
        button.backgroundColor = UIColor.white
        button.layer.shadowColor = UIColor.black.cgColor
        button.layer.shadowRadius = 3
        button.layer.shadowOpacity = 0.8
        button.layer.shadowOffset = CGSize.zero
        button.sizeToFit()
        button.frame = CGRect(origin: CGPoint(x: 10, y: 10), size: button.bounds.size)
        button.autoresizingMask = []
        view.addSubview(button)
        self.view = view
        self.button = button
        window.button = button

        let panner = UIPanGestureRecognizer(target: self, action: #selector(panDidFire(panner:)))
        button.addGestureRecognizer(panner)
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        snapButtonToSocket()
    }

    @objc func panDidFire(panner: UIPanGestureRecognizer) {
        let offset = panner.translation(in: view)
        panner.setTranslation(CGPoint.zero, in: view)
        var center = button.center
        center.x += offset.x
        center.y += offset.y
        button.center = center

        if panner.state == .ended || panner.state == .cancelled {
            UIView.animate(withDuration: 0.3) {
                self.snapButtonToSocket()
            }
        }
    }

    @objc func keyboardDidShow(note: NSNotification) {
        window.windowLevel = UIWindow.Level(rawValue: 0)
        window.windowLevel = UIWindow.Level(rawValue: CGFloat.greatestFiniteMagnitude)
    }

    private func snapButtonToSocket() {
        var bestSocket = CGPoint.zero
        var distanceToBestSocket = CGFloat.infinity
        let center = button.center
        for socket in sockets {
            let distance = hypot(center.x - socket.x, center.y - socket.y)
            if distance < distanceToBestSocket {
                distanceToBestSocket = distance
                bestSocket = socket
            }
        }
        button.center = bestSocket
    }

    private var sockets: [CGPoint] {
        let buttonSize = button.bounds.size
        let rect = view.bounds.insetBy(dx: 4 + buttonSize.width / 2, dy: 4 + buttonSize.height / 2)
        let sockets: [CGPoint] = [
            CGPoint(x: rect.minX, y: rect.minY),
            CGPoint(x: rect.minX, y: rect.maxY),
            CGPoint(x: rect.maxX, y: rect.minY),
            CGPoint(x: rect.maxX, y: rect.maxY),
            CGPoint(x: rect.midX, y: rect.midY)
        ]
        return sockets
    }

}

private class FloatingButtonWindow: UIWindow {

    var button: UIButton?

    init(scene: UIWindowScene) {
        super.init(windowScene: scene)
        backgroundColor = nil
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }


    fileprivate override func point(inside point: CGPoint, with event: UIEvent?) -> Bool {
        guard let button = button else { return false }
        let buttonPoint = convert(point, to: button)
        return button.point(inside: buttonPoint, with: event)
    }

}

in SceneDelegate:

var floatingButtonController: FloatingButtonController?

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    guard let scene = (scene as? UIWindowScene) else { return }
    floatingButtonController = FloatingButtonController(scene: scene)
    floatingButtonController?.button.addTarget(self, action: #selector(floatingButtonWasTapped), for: .touchUpInside)
}