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Merge pull request #55 from square/kve/keyboard-observation
ScrollView observes and adjusts for keyboard position
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BlueprintUICommonControls/Sources/Internal/KeyboardObserver.swift
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// | ||
// KeyboardObserver.swift | ||
// BlueprintUICommonControls | ||
// | ||
// Created by Kyle Van Essen on 2/16/20. | ||
// | ||
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import UIKit | ||
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protocol KeyboardObserverDelegate : AnyObject { | ||
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func keyboardFrameWillChange( | ||
for observer : KeyboardObserver, | ||
animationDuration : Double, | ||
options : UIView.AnimationOptions | ||
) | ||
} | ||
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/** | ||
Encapsulates listening for system keyboard updates, plus transforming the visible frame of the keyboard into the coordinates of a requested view. | ||
You use this class by providing a delegate, which receives callbacks when changes to the keyboard frame occur. You would usually implement | ||
the delegate somewhat like this: | ||
``` | ||
func keyboardFrameWillChange( | ||
for observer : KeyboardObserver, | ||
animationDuration : Double, | ||
options : UIView.AnimationOptions | ||
) { | ||
UIView.animate(withDuration: animationDuration, delay: 0.0, options: options, animations: { | ||
// Use the frame from the keyboardObserver to update insets or sizing where relevant. | ||
}) | ||
} | ||
``` | ||
Notes | ||
----- | ||
Implementation borrowed from Listable: | ||
https://github.com/kyleve/Listable/blob/master/Listable/Sources/Internal/KeyboardObserver.swift | ||
iOS Docs for keyboard management: | ||
https://developer.apple.com/library/archive/documentation/StringsTextFonts/Conceptual/TextAndWebiPhoneOS/KeyboardManagement/KeyboardManagement.html | ||
*/ | ||
final class KeyboardObserver { | ||
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private let center : NotificationCenter | ||
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weak var delegate : KeyboardObserverDelegate? | ||
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// | ||
// MARK: Initialization | ||
// | ||
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init(center : NotificationCenter = .default) { | ||
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self.center = center | ||
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/// We need to listen to both `will` and `keyboardDidChangeFrame` notifications. Why? | ||
/// When dealing with an undocked or floating keyboard, moving the keyboard | ||
/// around the screen does NOT call `willChangeFrame`; only `didChangeFrame` is called. | ||
/// Before calling the delegate, we compare `old.endingFrame != new.endingFrame`, | ||
/// which ensures that the delegate is notified if the frame really changes, and | ||
/// prevents duplicate calls. | ||
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self.center.addObserver(self, selector: #selector(keyboardFrameChanged(_:)), name: UIWindow.keyboardWillChangeFrameNotification, object: nil) | ||
self.center.addObserver(self, selector: #selector(keyboardFrameChanged(_:)), name: UIWindow.keyboardDidChangeFrameNotification, object: nil) | ||
} | ||
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private var latestNotification : NotificationInfo? | ||
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// | ||
// MARK: Handling Changes | ||
// | ||
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enum KeyboardFrame : Equatable { | ||
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/// The current frame does not overlap the current view at all. | ||
case nonOverlapping | ||
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/// The current frame does overlap the view, by the provided rect, in the view's coordinate space. | ||
case overlapping(frame: CGRect) | ||
} | ||
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/// How the keyboard overlaps the view provided. If the view is not on screen (eg, no window), | ||
/// or the observer has not yet learned about the keyboard's position, this method returns nil. | ||
func currentFrame(in view : UIView) -> KeyboardFrame? { | ||
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guard view.window != nil else { | ||
return nil | ||
} | ||
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guard let notification = self.latestNotification else { | ||
return nil | ||
} | ||
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let frame = view.convert(notification.endingFrame, from: nil) | ||
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if frame.intersects(view.bounds) { | ||
return .overlapping(frame: frame) | ||
} else { | ||
return .nonOverlapping | ||
} | ||
} | ||
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// | ||
// MARK: Receiving Updates | ||
// | ||
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private func receivedUpdatedKeyboardInfo(_ new : NotificationInfo) { | ||
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let old = self.latestNotification | ||
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self.latestNotification = new | ||
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/// Only communicate a frame change to the delegate if the frame actually changed. | ||
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if let old = old, old.endingFrame == new.endingFrame { | ||
return | ||
} | ||
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/** | ||
Create an animation curve with the correct curve for showing or hiding the keyboard. | ||
This is unfortunately a private UIView curve. However, we can map it to the animation options' curve | ||
like so: https://stackoverflow.com/questions/26939105/keyboard-animation-curve-as-int | ||
*/ | ||
let animationOptions = UIView.AnimationOptions(rawValue: new.animationCurve << 16) | ||
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self.delegate?.keyboardFrameWillChange( | ||
for: self, | ||
animationDuration: new.animationDuration, | ||
options: animationOptions | ||
) | ||
} | ||
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// | ||
// MARK: Notification Listeners | ||
// | ||
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@objc private func keyboardFrameChanged(_ notification : Notification) { | ||
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do { | ||
let info = try NotificationInfo(with: notification) | ||
self.receivedUpdatedKeyboardInfo(info) | ||
} catch { | ||
assertionFailure("Blueprint could not read system keyboard notification. This error needs to be fixed in Blueprint. Error: \(error)") | ||
} | ||
} | ||
} | ||
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extension KeyboardObserver | ||
{ | ||
struct NotificationInfo : Equatable { | ||
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var endingFrame : CGRect = .zero | ||
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var animationDuration : Double = 0.0 | ||
var animationCurve : UInt = 0 | ||
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init(with notification : Notification) throws { | ||
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guard let userInfo = notification.userInfo else { | ||
throw ParseError.missingUserInfo | ||
} | ||
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guard let endingFrame = (userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue else { | ||
throw ParseError.missingEndingFrame | ||
} | ||
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self.endingFrame = endingFrame | ||
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guard let animationDuration = (userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? NSNumber)?.doubleValue else { | ||
throw ParseError.missingAnimationDuration | ||
} | ||
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self.animationDuration = animationDuration | ||
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guard let animationCurve = (userInfo[UIResponder.keyboardAnimationCurveUserInfoKey] as? NSNumber)?.uintValue else { | ||
throw ParseError.missingAnimationCurve | ||
} | ||
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self.animationCurve = animationCurve | ||
} | ||
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enum ParseError : Error, Equatable { | ||
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case missingUserInfo | ||
case missingEndingFrame | ||
case missingAnimationDuration | ||
case missingAnimationCurve | ||
} | ||
} | ||
} |
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