在SwiftUI中开始文本字段编辑时检索键盘高度

Question

所以我有一个类，它有一个名为keyboardHeight的已发布变量，用于检索keyboardHeight:的值

import UIKit
class KeyboardHeightHelper: ObservableObject {
@Published var keyboardHeight: CGFloat = 0
init() {
self.listenForKeyboardNotifications()
}
private func listenForKeyboardNotifications() {
NotificationCenter.default.addObserver(forName: UIResponder.keyboardDidShowNotification,
object: nil,
queue: .main) { (notification) in
guard let userInfo = notification.userInfo,
let keyboardRect = userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect else { return }

self.keyboardHeight = keyboardRect.height
}

NotificationCenter.default.addObserver(forName: UIResponder.keyboardDidHideNotification,
object: nil,
queue: .main) { (notification) in
self.keyboardHeight = 0
}
}
}

然后，在ContentView中，我只有一个TextField，当你开始/停止编辑字段时，它应该打印键盘高度：

import SwiftUI
struct ContentView: View {
@State var textFieldText = ""
@ObservedObject var keyboardHeightHelper = KeyboardHeightHelper()
var body: some View {
VStack {
TextField("Text field",
text: $textFieldText, onEditingChanged: { _ in print("the keyboard height is (self.keyboardHeightHelper.keyboardHeight)") })

}
}
}

我遇到的问题是：当我不编辑文本字段，然后单击它时，它会打印键盘高度为0.0(我想这是因为它在显示键盘之前获取了keyboardHeight值，所以当时高度为0.0，因为看不到键盘(。当我按下回车键，键盘被关闭时，键盘的高度(适用于iPhone 8模拟器(将打印为260.0的正确值。我的问题是，当我开始编辑时，如何访问键盘的值？

Answer 1

试试这个。您可以使用SwiftUI视图的修改器将其集成：

extension UIResponder {
static var currentFirstResponder: UIResponder? {
_currentFirstResponder = nil
UIApplication.shared.sendAction(#selector(UIResponder.findFirstResponder(_:)), to: nil, from: nil, for: nil)
return _currentFirstResponder
}
private static weak var _currentFirstResponder: UIResponder?
@objc private func findFirstResponder(_ sender: Any) {
UIResponder._currentFirstResponder = self
}

var globalFrame: CGRect? {
guard let view = self as? UIView else { return nil }
return view.superview?.convert(view.frame, to: nil)
}
}

extension Publishers {
static var keyboardHeight: AnyPublisher<CGFloat, Never> {
let willShow = NotificationCenter.default.publisher(for: UIApplication.keyboardWillShowNotification)
.map { $0.keyboardHeight }

let willHide = NotificationCenter.default.publisher(for: UIApplication.keyboardWillHideNotification)
.map { _ in CGFloat(0) }

return MergeMany(willShow, willHide)
.eraseToAnyPublisher()
}
}
extension Notification {
var keyboardHeight: CGFloat {
return (userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect)?.height ?? 0
}
}

struct KeyboardAdaptive: ViewModifier {
@State private var bottomPadding: CGFloat = 0
func body(content: Content) -> some View {
GeometryReader { geometry in
content
.padding(.bottom, self.bottomPadding)
.onReceive(Publishers.keyboardHeight) { keyboardHeight in
let keyboardTop = geometry.frame(in: .global).height - keyboardHeight
let focusedTextInputBottom = UIResponder.currentFirstResponder?.globalFrame?.maxY ?? 0
self.bottomPadding = max(0, focusedTextInputBottom - keyboardTop - geometry.safeAreaInsets.bottom)
}
.animation(.easeOut(duration: 0.16))
}
}
}
extension View {
func keyboardAdaptive() -> some View {
ModifiedContent(content: self, modifier: KeyboardAdaptive())
}
}

用法：

struct ContentView: View {
@State private var text = ""

var body: some View {
VStack {
Spacer()

TextField("Enter something", text: $text)
.textFieldStyle(RoundedBorderTextFieldStyle())
}
.padding()
.keyboardAdaptive()//note this
}
}

多个在线来源的学分。

Answer 2

.onEditingChanged不是读取键盘高度的合适位置，因为您在点击TextField的那一刻就收到了这个回调，所以还没有显示键盘(因此也没有收到通知(。

相反，您可以显式侦听keyboardHeight属性发布者，并在其更改时得到确切通知(键盘通知同步执行，因此及时执行(

这是一个解决方案(用Xcode 12/iOS 14测试(

VStack {
TextField("Text field",
text: $textFieldText, onEditingChanged: { _ in  })
.onReceive(keyboardHeightHelper.$keyboardHeight) { value in
print("the keyboard height is (value)")
}
}