我如何在macOS上的SwiftUI视图中检测键盘事件?
我想要使用按键来控制特定屏幕上的元素,但是不清楚如何检测键盘事件,通常可以通过重写NSView
中的keyDown(_ event: NSEvent)
来完成。
commands
修饰符,该修饰符允许我们使用keyboardShortcut
视图修饰符声明关键输入。接下来需要一些方式将按键输入转发给子视图。以下是使用 Subject
的解决方案,但由于它不是引用类型,因此无法使用 environmentObject
进行传递 - 这确实是我们想要做的,因此我创建了一个小包装器,符合ObservableObject
并且为了方便起见,还包含 Subject
本身(通过 subject
转发)。.commands {
CommandMenu("Input") {
keyInput(.leftArrow)
keyInput(.rightArrow)
keyInput(.upArrow)
keyInput(.downArrow)
keyInput(.space)
}
}
.environmentObject(keyInputSubject)
然后一个子视图 GameView
可以通过 onReceive
监听事件,如下所示:
struct GameView: View {
@EnvironmentObject private var keyInputSubjectWrapper: KeyInputSubjectWrapper
@StateObject var game: Game
var body: some View {
HStack {
board
info
}.onReceive(keyInputSubjectWrapper) {
game.keyInput($0)
}
}
}
< p > 在 < code > CommandMenu 构建器中声明键的方法只有这个 < code > keyInput :
private extension ItsRainingPolygonsApp {
func keyInput(_ key: KeyEquivalent, modifiers: EventModifiers = .none) -> some View {
keyboardShortcut(key, sender: keyInputSubject, modifiers: modifiers)
}
}
extension KeyEquivalent: Equatable {
public static func == (lhs: Self, rhs: Self) -> Bool {
lhs.character == rhs.character
}
}
public typealias KeyInputSubject = PassthroughSubject<KeyEquivalent, Never>
public final class KeyInputSubjectWrapper: ObservableObject, Subject {
public func send(_ value: Output) {
objectWillChange.send(value)
}
public func send(completion: Subscribers.Completion<Failure>) {
objectWillChange.send(completion: completion)
}
public func send(subscription: Subscription) {
objectWillChange.send(subscription: subscription)
}
public typealias ObjectWillChangePublisher = KeyInputSubject
public let objectWillChange: ObjectWillChangePublisher
public init(subject: ObjectWillChangePublisher = .init()) {
objectWillChange = subject
}
}
// MARK: Publisher Conformance
public extension KeyInputSubjectWrapper {
typealias Output = KeyInputSubject.Output
typealias Failure = KeyInputSubject.Failure
func receive<S>(subscriber: S) where S : Subscriber, S.Failure == Failure, S.Input == Output {
objectWillChange.receive(subscriber: subscriber)
}
}
@main
struct ItsRainingPolygonsApp: App {
private let keyInputSubject = KeyInputSubjectWrapper()
var body: some Scene {
WindowGroup {
#if os(macOS)
ContentView()
.frame(idealWidth: .infinity, idealHeight: .infinity)
.onReceive(keyInputSubject) {
print("Key pressed: \($0)")
}
.environmentObject(keyInputSubject)
#else
ContentView()
#endif
}
.commands {
CommandMenu("Input") {
keyInput(.leftArrow)
keyInput(.rightArrow)
keyInput(.upArrow)
keyInput(.downArrow)
keyInput(.space)
}
}
}
}
private extension ItsRainingPolygonsApp {
func keyInput(_ key: KeyEquivalent, modifiers: EventModifiers = .none) -> some View {
keyboardShortcut(key, sender: keyInputSubject, modifiers: modifiers)
}
}
public func keyboardShortcut<Sender, Label>(
_ key: KeyEquivalent,
sender: Sender,
modifiers: EventModifiers = .none,
@ViewBuilder label: () -> Label
) -> some View where Label: View, Sender: Subject, Sender.Output == KeyEquivalent {
Button(action: { sender.send(key) }, label: label)
.keyboardShortcut(key, modifiers: modifiers)
}
public func keyboardShortcut<Sender>(
_ key: KeyEquivalent,
sender: Sender,
modifiers: EventModifiers = .none
) -> some View where Sender: Subject, Sender.Output == KeyEquivalent {
guard let nameFromKey = key.name else {
return AnyView(EmptyView())
}
return AnyView(keyboardShortcut(key, sender: sender, modifiers: modifiers) {
Text("\(nameFromKey)")
})
}
extension KeyEquivalent {
var lowerCaseName: String? {
switch self {
case .space: return "space"
case .clear: return "clear"
case .delete: return "delete"
case .deleteForward: return "delete forward"
case .downArrow: return "down arrow"
case .end: return "end"
case .escape: return "escape"
case .home: return "home"
case .leftArrow: return "left arrow"
case .pageDown: return "page down"
case .pageUp: return "page up"
case .return: return "return"
case .rightArrow: return "right arrow"
case .space: return "space"
case .tab: return "tab"
case .upArrow: return "up arrow"
default: return nil
}
}
var name: String? {
lowerCaseName?.capitalizingFirstLetter()
}
}
public extension EventModifiers {
static let none = Self()
}
extension String {
func capitalizingFirstLetter() -> String {
return prefix(1).uppercased() + self.lowercased().dropFirst()
}
mutating func capitalizeFirstLetter() {
self = self.capitalizingFirstLetter()
}
}
extension KeyEquivalent: CustomStringConvertible {
public var description: String {
name ?? "\(character)"
}
}
截至目前,SwiftUI中没有原生的API支持该功能。
以下仅是一个可能的解决方案演示。已在Xcode 11.4 / macOS 10.15.4上进行测试。
struct KeyEventHandling: NSViewRepresentable {
class KeyView: NSView {
override var acceptsFirstResponder: Bool { true }
override func keyDown(with event: NSEvent) {
print(">> key \(event.charactersIgnoringModifiers ?? "")")
}
}
func makeNSView(context: Context) -> NSView {
let view = KeyView()
DispatchQueue.main.async { // wait till next event cycle
view.window?.makeFirstResponder(view)
}
return view
}
func updateNSView(_ nsView: NSView, context: Context) {
}
}
struct TestKeyboardEventHandling: View {
var body: some View {
Text("Hello, World!")
.background(KeyEventHandling())
}
}
输出:
super.keyDown(with: event)
(这会告诉剩余的响应链该按键动作未被处理),那么错误声音就不再发出。 - Milossuper.keyDown(with: event)
。 - stef还有一种非常简单的解决方案,但只适用于特定类型的按键-您需要进行实验。只需创建带有 .keyboardShortcut
修改器的 Buttons
,但在视觉上隐藏它们。
Group {
Button(action: { goAway() }) {}
.keyboardShortcut(.escape, modifiers: [])
Button(action: { goLeft() }) {}
.keyboardShortcut(.upArrow, modifiers: [])
Button(action: { goDown() }) {}
.keyboardShortcut(.downArrow, modifiers: [])
}.opacity(0)
ZStack
的最顶层,按键甚至都不能触发动作。 - lazarevzubov
import SwiftUI import Combine
- Tom Grushka.tab
和.escape
似乎无法正常工作。 - Joannes