如何使底部按钮跟随 SwiftUI 中的键盘显示

Question

在下面的帮助下，我能够跟随键盘显示上的按钮。但是动画不能很好的应用。

import SwiftUI
import Combine
import UIKit

class KeyboardResponder: ObservableObject {
    let willset = PassthroughSubject<CGFloat, Never>()
    private var _center: NotificationCenter
    @Published var currentHeight: CGFloat = 0
    var keyboardDuration: TimeInterval = 0

    init(center: NotificationCenter = .default) {
        _center = center
        _center.addObserver(self, selector: #selector(keyBoardWillShow(notification:)), name: UIResponder.keyboardWillShowNotification, object: nil)
        _center.addObserver(self, selector: #selector(keyBoardWillHide(notification:)), name: UIResponder.keyboardWillHideNotification, object: nil)
    }

    deinit {
        _center.removeObserver(self)
    }

    @objc func keyBoardWillShow(notification: Notification) {
        if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
            currentHeight = keyboardSize.height

            guard let duration:TimeInterval = notification.userInfo?[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double else { return }
            keyboardDuration = duration
        }
    }

    @objc func keyBoardWillHide(notification: Notification) {
        currentHeight = 0
    }
}

import SwiftUI

struct Content: View {
    @ObservedObject var keyboard = KeyboardResponder()

    var body: some View {
        VStack {
            Text("text")

            Spacer()

            NavigationLink(destination: SubContentView()) {
                Text("Done")
            }
        }
        .padding(.bottom, keyboard.currentHeight)
        animation(Animation.easeInOut(duration: keyboard.keyboardDuration))
    }
}

enter image description here

Answer 1

您的主要问题是您使用的是隐式动画。不仅它可能会为您可能不想制作动画的东西制作动画，而且您永远不应该在容器上应用 .animation() 。在 SwiftUI 文档中的几个警告中，这是其中之一：

Use this modifier on leaf views rather than container views. The animation applies to all child views within this view; calling animation(_:) on a container view can lead to unbounded scope.

来源：https://developer.apple.com/documentation/swiftui/view/3278508-animation

修改后的代码删除了隐式 .animation() 调用，并将其替换为两个隐式 withAnimation 闭包。

我还用 keyboardFrameEndUserInfoKey 替换了 keyboardFrameEndUserInfoKey，第二次调用给出了无用的几何图形。

class KeyboardResponder: ObservableObject {
    let willset = PassthroughSubject<CGFloat, Never>()
    private var _center: NotificationCenter
    @Published var currentHeight: CGFloat = 0
    var keyboardDuration: TimeInterval = 0

    init(center: NotificationCenter = .default) {
        _center = center
        _center.addObserver(self, selector: #selector(keyBoardWillShow(notification:)), name: UIResponder.keyboardWillShowNotification, object: nil)
        _center.addObserver(self, selector: #selector(keyBoardWillHide(notification:)), name: UIResponder.keyboardWillHideNotification, object: nil)
    }

    deinit {
        _center.removeObserver(self)
    }

    @objc func keyBoardWillShow(notification: Notification) {
        if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {

            guard let duration:TimeInterval = notification.userInfo?[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double else { return }
            keyboardDuration = duration

            withAnimation(.easeInOut(duration: duration)) {
                self.currentHeight = keyboardSize.height
            }

        }
    }

    @objc func keyBoardWillHide(notification: Notification) {
        guard let duration:TimeInterval = notification.userInfo?[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double else { return }

        withAnimation(.easeInOut(duration: duration)) {
            currentHeight = 0
        }
    }
}


struct ContentView: View {
    @ObservedObject var keyboard = KeyboardResponder()

    var body: some View {

        return VStack {
            Text("text \(keyboard.currentHeight)")

            TextField("Enter text", text: .constant(""))
            Spacer()

            NavigationLink(destination: Text("SubContentView()")) {
                Text("Done")
            }
        }
        .padding(.bottom, keyboard.currentHeight)
//        .animation(Animation.easeInOut(duration: keyboard.keyboardDuration))
    }
}

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