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Easy way to get your view controllers to respect appearance of the keyboard.
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| // KeyboardAvoidable | |
| // Roy McKenzie | |
| protocol KeyboardAvoidable: class { | |
| func addKeyboardObservers(customBlock: ((CGFloat) -> Void)?) | |
| func removeKeyboardObservers() | |
| var layoutConstraintsToAdjust: [NSLayoutConstraint] { get } | |
| } | |
| var KeyboardShowObserverObjectKey: UInt8 = 1 | |
| var KeyboardHideObserverObjectKey: UInt8 = 2 | |
| extension KeyboardAvoidable where Self: UIViewController { | |
| var keyboardShowObserverObject: NSObjectProtocol? { | |
| get { | |
| return objc_getAssociatedObject(self, | |
| &KeyboardShowObserverObjectKey) as? NSObjectProtocol | |
| } | |
| set { | |
| objc_setAssociatedObject(self, | |
| &KeyboardShowObserverObjectKey, | |
| newValue, | |
| .OBJC_ASSOCIATION_RETAIN_NONATOMIC) | |
| } | |
| } | |
| var keyboardHideObserverObject: NSObjectProtocol? { | |
| get { | |
| return objc_getAssociatedObject(self, | |
| &KeyboardHideObserverObjectKey) as? NSObjectProtocol | |
| } | |
| set { | |
| objc_setAssociatedObject(self, | |
| &KeyboardHideObserverObjectKey, | |
| newValue, | |
| .OBJC_ASSOCIATION_RETAIN_NONATOMIC) | |
| } | |
| } | |
| func addKeyboardObservers(customBlock: ((CGFloat) -> Void)? = nil) { | |
| keyboardShowObserverObject = NotificationCenter.default.addObserver(forName: .UIKeyboardWillShow, | |
| object: nil, | |
| queue: nil) { [weak self] notification in | |
| guard let height = self?.getKeyboardHeightFrom(notification: notification) else { return } | |
| if let customBlock = customBlock { | |
| customBlock(height) | |
| return | |
| } | |
| self?.layoutConstraintsToAdjust.forEach { | |
| $0.constant = height | |
| } | |
| UIView.animate(withDuration: 0.2){ | |
| self?.view.layoutIfNeeded() | |
| } | |
| } | |
| keyboardHideObserverObject = NotificationCenter.default.addObserver(forName: .UIKeyboardWillHide, | |
| object: nil, | |
| queue: nil) { [weak self] notification in | |
| if let customBlock = customBlock { | |
| customBlock(0) | |
| return | |
| } | |
| self?.layoutConstraintsToAdjust.forEach { | |
| $0.constant = 0 | |
| } | |
| UIView.animate(withDuration: 0.2){ | |
| self?.view.layoutIfNeeded() | |
| } | |
| } | |
| } | |
| private func getKeyboardHeightFrom(notification: Notification) -> CGFloat { | |
| guard let info = notification.userInfo else { return .leastNormalMagnitude } | |
| guard let value = info[UIKeyboardFrameEndUserInfoKey] as? NSValue else { return .leastNormalMagnitude } | |
| let keyboardSize = value.cgRectValue.size | |
| return keyboardSize.height | |
| } | |
| func removeKeyboardObservers() { | |
| if let keyboardShowObserverObject = keyboardShowObserverObject { | |
| NotificationCenter.default.removeObserver(keyboardShowObserverObject) | |
| } | |
| if let keyboardHideObserverObject = keyboardHideObserverObject { | |
| NotificationCenter.default.removeObserver(keyboardHideObserverObject) | |
| } | |
| keyboardShowObserverObject = nil | |
| keyboardHideObserverObject = nil | |
| } | |
| } | |
| // Example Implementation | |
| // final class NiceViewController: UIViewController { | |
| // | |
| // @IBOutlet weak var scrollViewBottomConstraint: NSLayoutConstraint! | |
| // | |
| // override func viewWillAppear(animated: Bool) { | |
| // super.viewWillAppear(animated) | |
| // | |
| // addKeyboardObservers() | |
| // } | |
| // | |
| // override func viewWillDisappear(animated: Bool) { | |
| // super.viewWillDisappear(animated) | |
| // | |
| // removeKeyboardObservers() | |
| // } | |
| // } | |
| // | |
| // extension NiceViewController: KeyboardAvoidable { | |
| // | |
| // var layoutConstraintsToAdjust: [NSLayoutConstraint] { | |
| // return [scrollViewBottomConstraint] | |
| // } | |
| // } |
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Don't removeKeyboardObservers() should be called on the beginning of addKeyboardObservers() to prevent issues when it was called more than once?